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The efficiency of Bembidion lampros (Herbst) (Coleoptera:Carabidae) as a predator of Hylemya brassicae.. 1976

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THE EFFICIENCY OF BEMBIDION LAMPROS (HERBST) (COLEOPTERA:CARABIDAE) AS A PREDATOR OF HYLEMYA BRASSICAE (BOUCHE) (DIPTERA:ANTHOMYIIDAE) EGGS AND THE EFFECTS OF SEVERAL INSECTICIDES ON THE BEETLE by ADEGBOYEGA ADEKUNLE OBADOFIN B . S c , U n i v e r s i t y of IFE, 1971 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of P l a n t Science. We accept t h i s t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1976 (c) Adegboyega Adekunle Obadofin, 1976 In p re sent ing t h i s t he s i s in p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree tha t permiss ion fo r ex ten s i ve copying of t h i s t he s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r ep re sen ta t i ve s . It i s understood that copying or p u b l i c a t i o n o f t h i s t he s i s f o r f i n a n c i a l ga in s h a l l not be a l lowed without my w r i t t e n permi s s ion . Department o f ' P l a n t S c i e n c e The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date A p r i l 1976 ABSTRACT The e f f i c i e n c y of the c a r a b i d b e e t l e , Bembidion lampros (Herbst) as a predator of the eggs of Hylemya b r a s s i c a e (Bouch§) and the e f f e c t s of the i n s e c t i c i d e s D i p e l , methomyl and c h l o r f e n v i n p h o s on the b e e t l e were s t u d i e d by i n t r o d u c i n g some B. lampros i n t o experimental p l o t s of B r u s s e l s s p r o u t s and r e s t r i c t i n g t h e i r movements by surrounding the p l o t s w i t h polythene b a r r i e r s . More eggs were l a i d i n the f i r s t than i n the second g e n e r a t i o n of the cabbage r o o t f l y . There was p r o g r e s s - i v e decrease i n the number o f r o o t f l y eggs and the number of B. lampros as the p l a n t s matured. During the f i r s t g e n e r a t i o n the u n t r e a t e d c o n t r o l had s i g n i f i c a n t l y more eggs than the o t h e r treatments. Egg p r e d a t i o n by B. lampros r e s u l t e d i n a 45% r e d u c t i o n . In p l o t s c o n t a i n i n g B. lampros and t r e a t e d w i t h methomyl, D i p e l or c h l o r f e n v i n p h o s , the numbers of eggs were reduced by 35, 44 and 66% r e s p e c t i v e l y . L a b o r a t o r y t o x i c i t y s t u d i e s showed t h a t methomyl at 1 g/ l i t r e produced 100% m o r t a l i t y of B. lampros one day a f t e r treatment. When the r a t e was reduced t o 1/2, 1/4 and 1/8, the m o r t a l i t y of B. lampros dropped to 70, 40 and 20% r e s p e c t - i v e l y . D i p e l [ B a c i l l u s t h u r i n q i e n s i s B e r l i n e r (16000 IU/mg)] at 1 g / l i t r e and 5 g / l i t r e and c h l o r f e n v i n p h o s a t 10 ppm and 40 ppm; produced no m o r t a l i t y t h r e e days a f t e r t r e a t - ment. F o l i a r a p p l i c a t i o n of methomyl f o r aphid c o n t r o l i i i i n the f i e l d s i g n i f i c a n t l y reduced the B. lampros p o p u l a t i o n . There was no s i g n i f i c a n t e f f e c t on B. lampros when D i p e l was a p p l i e d as a f o l i a r spray t o c o n t r o l l e p i d o p t e r o u s l a r v a e . C h l o r f e n v i n p h o s granules a p p l i e d once e a r l y i n the season as a subsurface treatment prevented damage by cabbage maggot and was not t o x i c t o B. lampros. Cabbage maggot damage was not severe enough to cause s i g n i f i c a n t r e d u c t i o n i n y i e l d a t h a r v e s t but examination of r o o t s showed t h a t u n t r e a t e d p l o t s had s i g n i f i c a n t l y more maggot damage than other treatments. The damage index ranged from 2.5 f o r u n t r e a t e d p l a n t s to 0.0 i n p l a n t s from p l o t s t r e a t e d w i t h c h l o r f e n v i n p h o s and c o n t a i n i n g B. lampros. Although d i f f e r e n c e s were not s i g n i f i c a n t , the numbers of o v e r w i n t e r i n g r o o t f l y p u p a r i a were h i g h e s t i n u n t r e a t e d p l o t s . S i g n i f i c a n t l y more empty p u p a r i a , i n d i c a t i n g second g e n e r a t i o n f l y emergence, were a l s o found i n the u n t r e a t e d p l o t s . Besides B. lampros, other c a r a b i d s removed from the experimental p l o t s i n c l u d e d : Harpalus a f f i n i s Schr., Amara spp., C a l a t h u s f u s c i p e s Goeze, P t e r o s t i c h u s melanarius 111. and other Bembidion spp., i n d e c r e a s i n g order of abundance. B. lampros alone does not g i v e complete p r o t e c t i o n a g a i n s t r o o t maggot, e s p e c i a l l y i f f l y o v i p o s i t i o n i s very heavy d u r i n g the f i r s t g e n e r a t i o n when the b e e t l e i s most e f f e c t i v e . But the b e e t l e w i l l go a long way to suppress p a r t of the p o p u l a t i o n . The use of n o n - s e l e c t i v e i n s e c t i - i v c i d e s f o r c o n t r o l of p e s t s of B r a s s i c a may l e a d t o r e d u c t - i o n of B. lampros p o p u l a t i o n s and a consequent i n c r e a s e i n cabbage maggot a t t a c k . V TABLE OF CONTENTS 1. INTRODUCTION 1 2. LITERATURE REVIEW 4 2.1 Bembidion lampros (Herbst) ( C o l e o p t e r a : Carabidae) 4 2.1.1 D i s t r i b u t i o n and abundance 4 2.1.2 L i f e h i s t o r y 5 2.1.3 Economic importance 6 2.2 Cabbage maggot, Hylemya b r a s s i c a e (Bouche) (D iptera:AnthomyTidae) 8 2.2.1 Generation and l i f e c y c l e 8 2.2.2 C o n t r o l 10 2.3 Other major p e s t s of b r a s s i c a s (aphids and l e p i d o p t e r a ) 15 2.3.1 E f f e c t i v e n e s s o f methomyl on aphids and l e p i d o p t e r a 15 2.3.2 E f f e c t i v e n e s s of B a c i l l u s t h u r i n g i e n s i s B e r l i n e r on l e p i d o p t e r a 16 2.4 T o x i c i t y of i n s e c t i c i d e s on n a t u r a l enemies of cabbage r o o t f l y 17 2.4.1 D i r e c t e f f e c t s of i n s e c t i c i d e s 17 2.4.2 I n d i r e c t e f f e c t s of i n s e c t i c i d e s 19 2.5 P r o s p e c t s of i n t e g r a t e d c o n t r o l of b r a s s i c a p e s t s 21 2.5.1 S e l e c t i v i t y i n i n s e c t i c i d e s 21 2.5.2 Mode of a p p l i c a t i o n 23 3. MATERIALS AND METHODS 2 5 3.1 D e s c r i p t i o n of s i t e and pretreatment c u l t i v a t i o n 25 v i 3.2 Crop and l a y o u t of f i e l d 25 3.3 Design of experiment and treatments 29 3.4 Release of r o o t f l y p u p a r i a 30 3.5 I n t r o d u c t i o n and sampling of B. lampros p o p u l a t i o n 33 3.6 Egg counts 37 3.7 I n s e c t i c i d e treatments 39 3.8 C u l t u r a l p r a c t i c e s 39 3.9 Harvest 40 3.10 Puparia counts 4 2 3.11 La b o r a t o r y t e s t s 43 4. OBSERVATION AND RESULTS 45 4.1 Development of cabbage r o o t f l y i n f e s t a t i o n 45 4.2 Occurrence of B. lampros 45 4.3 E f f e c t o f B. lampros on cabbage r o o t f l y eggs 49 4.4 E f f e c t s of i n s e c t i c i d e treatment on B. lampros 55 4.5 C a r a b i d b e e t l e s o t h e r than B. lampros 59 4.6 Y i e l d and s u r v i v a l of B r u s s e l s sprout p l a n t s 62 4.7 Cabbage maggot damage 64 5. DISCUSSION 67 5.1 L e v e l of o v i p o s i t i o n and consequent i n f e s t a t i o n 67 5.2 E f f e c t o f weather on o v i p o s i t i o n by cabbage r o o t f l y 68 5.3 P o p u l a t i o n t r e n d o f B. lampros 69 5.4 P r e d a t i o n of the egg stage of cabbage r o o t f l y by B. lampros 71 v i i 5.5 S u s c e p t i b i l i t y of B. lampros t o i n s e c t i c i d e treatments 5.6 I n t e g r a t e d c o n t r o l of i n s e c t p ests of stem b r a s s i c a s 6. SUMMARY AND CONCLUSIONS 7. LITERATURE CITED APPENDIX TABLE 1 APPENDIX TABLE 2 APPENDIX TABLE 3 APPENDIX TABLE 4 APPENDIX TABLE 5 APPENDIX TABLE 6 APPENDIX TABLE 7 Average number of eggs/plant date f o r each treatment a t 2 days i n t e r v a l May - August 1975 Average number of B. lampros taken from p i t f a l l t r a p s (4/plot) each date a t 2 days i n t e r v a l f o r the v a r i o u s treatments Weekly counts of cabbage r o o t f l y eggs on B r u s s e l s sprout p l a n t s (4 samples/plot) d u r i n g the growing season (May - August) Number of B. lampros taken from p i t f a l l t r a p s (4/plot) i n 20 p l o t s i n s i d e the b a r r i e r each week f o r the v a r i o u s treatments May - August 1975 Weekly mean of cabbage r o o t f l y eggs and the corre s p o n d i n g mean of B. lampros f o r the v a r i o u s treatments combined Number of other c a r a b i d s taken i n s i d e the b a r r i e r from 80 p i t f a l l t r a p s from May - August 1975 Weekly t o t a l s of c a r a b i d s p e c i e s caught o u t s i d e the b a r r i e r from 20 p i t f a l l t r a p s May - August 1975 APPENDIX TABLE 8 The numbers and weights of B r u s s e l s sprout p l a n t s a t h a r v e s t 73 76 78 80 99 102 105 106 107 108 110 111 APPENDIX TABLE 9 Root examination and number of cabbage r o o t f l y pup a r i a per p l a n t 112 v i i i APPENDIX TABLE 10 Percentage m o r t a l i t y of B. lampros 1, 2 and ,4 days a f t e r exposure t o f r e s h i n s e c t i c i d e - t r e a t e d s o i l 113 APPENDIX TABLE 11 Names o f p e s t i c i d e s and chemical d e f i n i t i o n o f compounds used f o r p r e v e n t i n g cabbage maggot damage i n Canada and other p a r t s o f the world 115 APPENDIX TABLE 12 Names of p e s t i c i d e s and chemical d e f i n i t i o n of compounds used f o r the c o n t r o l o f aphids and l e p i d o p t e r o u s l a r v e on b r a s s i c a s 116 LIST OF TABLES ix Table I Table I I Table I I I Ta b l e IV Table V Table VI Table V I I Table V I I I T a b l e IX Ta b l e X Ta b l e XI N a t u r a l p o p u l a t i o n s o f c a r a b i d b e e t l e s taken from p i t f a l l t r a p s i n s i d e the b a r r i e r i n the f o u r u n t r e a t e d p l o t s (64 sq m), May - August 1975. Monthly averages of cabbage r o o t f l y eggs May - August 197 5. The mean number of eggs sampled from p l a n t s d u r i n g the f i r s t and second g e n e r a t i o n of the cabbage r o o t f l y i n 1975. Percentage r e d u c t i o n i n egg numbers due to p r e d a t i o n by B. lampros f o r the v a r i o u s treatments durxng the f i r s t g e n e r a t i o n of cabbage r o o t f l y . Percentage m o r t a l i t y of B. lampros exposed t o i n s e c t i c i d e - t r e a t e d s o i l , sampled p e r i o d i c a l l y a f t e r a p p l i c a t i o n , Monthly t o t a l s of B. lampros taken from p i t f a l l t r a p s (4/plot) i n s i d e the b a r r i e r f o r the v a r i o u s treatments May - August 197 5. Numbers of c a r a b i d b e e t l e s other than B. lampros, taken i n s i d e the b a r r i e r from 80 p i t f a l l t r a p s i n the v a r i o u s treatments May - August 1975. Numbers of c a r a b i d b e e t l e s taken from 20 p i t f a l l t r a p s o u t s i d e the b a r r i e r May - September 1975. Percentage s u r v i v a l and mean weight of f r e s h B r u s s e l s sprout p l a n t s a t h a r v e s t . Average index per p l a n t f o r maggot damage a f t e r v a r i o u s treatments (20 p l a n t s , 5 / p l o t ) . Average number of cabbage r o o t f l y p u p a r i a per p l a n t (20 p l a n t s , 5/plot) a t h a r v e s t . 48 51 52 54 56 58 60 61 63 65 66 X LIST OF FIGURES F i g u r e 1 Layout of experimental f i e l d showing some 27 of the p l o t s , the polythene b a r r i e r s and B r u s s e l s sprout t r a n s p l a n t s a t the e a r l y stages. F i g u r e 2 P o s i t i o n of p i t f a l l t r a p w i t h i n an 28 experimental p l o t . F i g u r e 3 Mass r e a r i n g of cabbage r o o t f l y f o r f i e l d 31 r e l e a s e a t A g r i c u l t u r e Canada l a b o r a t o r y , Vancouver. F i g u r e 4 Stages i n the l i f e c y c l e of the cabbage 32 r o o t f l y , Hylemya b r a s s i c a e (Bouch£). F i g u r e 5 The c a r a b i d s p e c i e s taken from p i t f a l l 35, 36 t r a p s i n the experimental f i e l d . F i g u r e 6 Counting of H. b r a s s i c a e eggs i n an 38 experimental p l o t . F i g u r e 7 Root maggot damage c a t e g o r i e s i n 41 B r u s s e l s s p r o u t s . F i g u r e 8 O v i p o s i t i o n by the cabbage r o o t f l y 46 Hylemya b r a s s i c a e (Bouche1) : average number of eggs/plant on 52 dates f o r each treatment, May - August 1975. F i g u r e 9 P o p u l a t i o n trends of B. lampros: 47 average numbers taken every 2 days from p i t f a l l t r a p s i n each p l o t (4 t r a p s / p l o t ) f o r each treatment May - August 1975. F i g u r e 10 Occurrence of Hylemya b r a s s i c a eggs 50 and c o r r e s p o n d i n g BembTdion lampros p o p u l a t i o n (weekly average) m the experimental f i e l d . x i ACKNOWLEDGEMENT I wish to express my s i n c e r e thanks t o Dr. D.G. F i n l a y s o n , Entomology D i v i s i o n , Research S t a t i o n , A g r i c u l t u r e Canada, Vancouver f o r h i s guidance and s u p e r v i s i o n throughout t h i s study. His he l p i n p r e p a r a t i o n of the photographs i n the t h e s i s i s g r a t e f u l l y acknowledged. I am a l s o indebted t o Dr. H.R. MacCarthy, Head, Entomology D i v i s i o n , Research S t a t i o n , A g r i c u l t u r e Canada, Vancouver f o r suggesting t h i s t o p i c and f o r h i s h e l p f u l d i s c u s s i o n and encouragement d u r i n g the f i e l d and w r i t i n g stages of my p r o j e c t . I a l s o thank my f a c u l t y super- v i s o r , Dr. J.H. Myers, I n s t i t u t e o f Animal Resouces Ecology, U.B.C, f o r her keen i n t e r e s t and a d v i c e on the p r o j e c t . Thanks to members of my committee, Dr. V.C. Runeckles, Dr. H.R. MacCarthy, Dr. D.G. F i n l a y s o n and Dr. J.H. Myers f o r h e l p f u l suggestions and c r i t i c i s m s i n the w r i t i n g o f the t h e s i s . I would l i k e t o express my a p p r e c i a t i o n to Mr. C.J. Campbell, T e c h n i c i a n , Research S t a t i o n , A g r i c u l t u r e Canada, Vancouver f o r h i s t e c h n i c a l a s s i s t a n c e i n the f i e l d and l a b o r a t o r y s t u d i e s . His a s s i s t a n c e i n i d e n t i f y i n g some of the c a r a b i d b e e t l e s i s g r a t e f u l l y acknowledged. Acknowledgement i s a l s o g i v e n t o Dr. G.W. Eaton, Department of P l a n t S c i e n c e , U.B.C., f o r h i s a d v i c e on s t a t i s t i c a l a n a l y s i s . S p e c i a l thanks go t o Mrs. R. Iy e r , T e c h n i c i a n , I.A.R.E., U.B.C; Miss 0. P i e d r a h i t a and Miss K. Fr y f o r t h e i r f i e l d a s s i s t a n c e d u r i n g the summer of 1975. x i i I am g r a t e f u l t o the D i r e c t o r , Research S t a t i o n , A g r i c u l t u r e Canada, Vancouver f o r p e r m i t t i n g my use of the f a c i l i t i e s a v a i l a b l e at the Research S t a t i o n . The c l o s e c o o p e r a t i o n of other members of the s t a f f , p a r t i c u l a r l y the l i b r a r y s t a f f a t the S t a t i o n , i s g r a t e f u l l y acknowledged. F i n a l l y , I am g r a t e f u l to the F e d e r a l Department of A g r i c u l t u r e , F e d e r a l R e p u b l i c of N i g e r i a f o r p r o v i d i n g f i n a n c i a l a i d d u r i n g the course of t h i s study. 1. INTRODUCTION The cabbage maggot, Hylemya b r a s s i c a e (Bouch<§) i s a p a r t i c u l a r l y d e s t r u c t i v e p e s t of cabbage, B r u s s e l s s p r o u t s , c a u l i f l o w e r , r a d i s h , t u r n i p , swede and rutabaga (Lovett, 1913; P a i l l o t , 1914; Schoene, 1916; B r i t t a i n , 1927; Smith, 1927). In Canada, i n a review by Beirne (1971), i t i s s a i d t o be the most important vege t a b l e pest i n Newfoundland and Labrador, the most important s i n g l e f a c t o r l i m i t i n g t u r n i p p r o d u c t i o n i n New Brunswick, one of the main f a c t o r s l i m i t i n g h i g h q u a l i t y rutabaga p r o d u c t i o n i n A l b e r t a , and the most s e r i o u s pest of cabbage and c a u l i f l o w e r i n B r i t i s h Columbia where i t i s a c r i t i - c a l f a c t o r i n the p r o d u c t i o n o f e a r l y cabbage i n the c o a s t a l r e g i o n s . In c e r t a i n seasons i n North America, as many as 90% of the p l a n t s i n some b r a s s i c a crops may be k i l l e d (Forbes and King, 1957) and t h i s must s u r e l y a l s o be the case i n oth e r c o u n t r i e s where i n f e s t a t i o n s are severe (Coaker and F i n c h , 1971). In England and Wales, crop l o s s e s of e d i b l e b r a s s i c a s can be as high as 60% but the average estimate, assuming t h a t the crop l o s s i s lower i n wet than i n dry yea r s , i s nearer t o 24% ( S t r i c k l a n d , 1965). P l a n t s a t t a c k e d as s e e d l i n g s or a f t e r t r a n s p l a n t i n g are u s u a l l y s e v e r e l y damaged and they o f t e n d i e because the combination of l a r v a l f e e d i n g and subsequent r o t t i n g d e s t r o y the e n t i r e r o o t system (Coaker and F i n c h , 1971). V i g o r o u s l y growing stem b r a s s i c a s can support heavy p o p u l a t i o n s o f l a r v a e without showing s i g n s of a t t a c k but when the l a r v a e d i r e c t l y 2. a t t a c k t h a t p a r t of the p l a n t which i s used f o r human consumption, e.g. swede and r a d i s h , even a s m a l l amount of damage lowers the q u a l i t y . The presence of l a r v a e w i t h i n the buttons of B r u s s e l s sprouts i s a s e r i o u s problem i n crops grown f o r p r o c e s s i n g because, even though the i n c i d e n c e of damage i s very low, the crop may be r e j e c t e d (Coaker, 1967). C e r t a i n p a r a s i t e s and p r e d a t o r s have been i d e n t i f i e d and these e x e r t some measure of c o n t r o l by f e e d i n g on the immature stages of the cabbage r o o t f l y (Wishart e t a l . , 1956; Hughes, 1959; Wright e t a l . , 1960; Read, 1962; M i t c h e l l , 1963a; Coaker and W i l l i a m s , 1963). The s i n g l e - f a c t o r approach to i n s e c t c o n t r o l , i n v o l v i n g s o l e r e l i a n c e on i n s e c t i c i d e s , has the f o l l o w i n g l i m i t a t i o n s : 1) s e l e c t i o n f o r r e s i s t a n c e i n p e s t p o p u l a t i o n s , 2) d e s t r u c t i o n of b e n e f i c i a l s p e c i e s , 3) resurgence of t r e a t e d p o p u l a t i o n s , 4) outbreaks of secondary p e s t s , 5) r e s i d u e i n feeds, foods and the environment, and 6) hazards to humans and the environment (Luckmann and M e t c a l f , 1975). S t r a i n s of cabbage maggots r e s i s t a n t to c h l o r i n a t e d hydrocarbons have a l r e a d y appeared i n most c o u n t r i e s ( F i n l a y s o n , 1962; Howitt and C o l e , 1962; H a r r i s e t a l . , 1962; Chapman and P i t r e , 1963; Coaker e t al_. , 1963). I t has a l s o been found t h a t most of the recommended i n s e c t i c i d e s are t o x i c to the n a t u r a l p a r a s i t e s and p r e d a t o r s of the cabbage r o o t f l y (Morris, 1960; Coaker, 1966; Edwards e t a l . , 1970; C r i t c h l e y , 1972b; Hassan, 1973). Any r e d u c t i o n i n the numbers of p a r a s i t e s and p r e d a t o r s , mostly c a r a b i d s and s t a p h y l i n i d s would cause a p r o p o r t i o n a t e i n c r e a s e i n s u r v i v a l and numbers of 3. the p e s t and of the amount of damage on b r a s s i c a r o o t s ( P i c k e t t , 1959; Coaker and W i l l i a m s , 1963; Coaker, 1965). Luckmann and M e t c a l f (1975), remark t h a t i t i s l i k e l y t h a t most i n s e c t p e s t - management programs w i l l u t i l i z e i n s e c t i c i d e s , but t h i s use must be compatible w i t h other c o n t r o l s and c o n s i s t e n t w i t h the p e s t - management concept. The prese n t study e v a l u a t e d the e f f i c i e n c y of the c a r a b i d b e e t l e , Bembidion.lampros (Herbst) as a p r e d a t o r of cabbage r o o t f l y eggs and gauged the e f f e c t s of c e r t a i n i n s e c t i c i d e s on the b e e t l e w i t h a view to a p p l y i n g an i n t e g r a t e d c o n t r o l program f o r the pest complex of b r a s s i c a crops. 4. 2. LITERATURE REVIEW 2.1 Bembidion lampros (Herbst) (ColeopterarCarabidae) 2.1.1 D i s t r i b u t i o n and abundance Bembidion lampros i s a ground b e e t l e i n the f a m i l y Carabidae, a n a t i v e of Europe and A s i a where i t i s v e r y w i d e l y d i s t r i b u t e d (Hatch, 1953). T h i s s p e c i e s was f i r s t recorded i n North America i n southwest B r i t i s h Columbia i n 1946 but the extent of i t s prese n t d i s t r i b u t i o n i n North America i s not completely known (F i n l a y s o n and Campbell, 1974; F i n l a y s o n e t a l . , 1975). In cabbage p l o t s B. lampros occurs i n higher numbers on bare ground between the p l a n t s than under the p l a n t s , and the p o p u l a t i o n of a d u l t s found between the p l a n t s decreases as the p l a n t s i n c r e a s e i n s i z e ( M i t c h e l l , 1963a). They appear to p r e f e r bare or s p a r s e l y covered ground between p l a n t s t o shaded ground. M i t c h e l l (1963b) showed t h a t the numbers of B. lampros were i n v e r s e l y r e l a t e d to the age of each crop, and d i r e c t l y r e l a t e d t o the amount of bare ground on each p l o t . 5. 2.1.2 L i f e h i s t o r y The f o l l o w i n g d e s c r i p t i o n of the l i f e h i s t o r y of B. lampros i s taken from M i t c h e l l (1963a). A d u l t males and females are found on the ground d u r i n g A p r i l and May. C o p u l a t i o n occurs between l a t e A p r i l and l a t e J u l y and g r a v i d females p a r t i c u l a r l y those ready f o r o v i p o s i t i o n r e a d i l y move i n t o deep cracks i n the s o i l , a behaviour p a t t e r n which i s not t y p i c a l of non-breeding a d u l t s except d u r i n g the w i n t e r . The t o t a l number of eggs produced i s not known but one batch c o n s i s t i n g of about 16 eggs i s l a i d a t a time. The eggs are very s m a l l w i t h no c h o r i o n markings or other e x t e r n a l c h a r a c t e r i s t i c s and measure about 0.55 x 0.34 mm. They hatch a f t e r 12 to 15 days at 18°C. The l a r v a e are found between June and August of the same year and there are t h r e e i n s t a r s . The l a r v a e are s l e n d e r , about 3 mm long depending on the i n s t a r . Pupation takes p l a c e a t the end of the t h i r d i n s t a r . A d u l t s emerge from the pupae between J u l y and September and some a d u l t s s u r v i v e f o r a year or more. Young a d u l t s are p a l e and u s u a l l y take a few days to darken. The a d u l t s are very s m a l l , about 3.5 mm long, b l a c k and s h i n y , w i t h a b r a s s y or aeneous l u s t r e . The l e g s are p a l e r e d d i s h and prothorax i s s t r o n g l y c o n s t r i c t e d a t the base. Carabids have g e n e r a l l y one g e n e r a t i o n per year and can be c o n v e n i e n t l y d i v i d e d i n t o s p r i n g breeders which g i v e r i s e to summer l a r v a e and autumn breeders whose l a r v a e occur d u r i n g the w i n t e r months ( L i n d r o t h , 1949). B. lampros c l e a r l y belongs to the former group ( M i t c h e l l , 1963a). 6. 2.1.3 Economic importance Wright e t a l . , (1956) and Wishart e t a l . , (1956) f i r s t r e c o g n i z e d the importance of c e r t a i n s p e c i e s of c a r a b i d and s t a p h y l i n i d b e e t l e s as p r e d a t o r s of the immature stages of the cabbage r o o t f l y . Hughes and S a l t e r (1959) and Coaker and W i l l i a m s (19 63) have shown t h a t some c a r a b i d and s t a p h y l i n i d b e e t l e s commonly found i n the s o i l can be e f f e c t i v e p r e d a t o r s of cabbage r o o t f l y eggs and l a r v a e , and t h a t r e d u c t i o n i n t h e i r numbers can i n c r e a s e the s u r v i v a l of the p e s t (Wright et a l . , 1960; Coaker, 1965). In B r i t a i n , p r e d a t o r y b e e t l e s e x e r t a c o n s i d e r a b l e n a t u r a l check on cabbage r o o t f l y p o p u l a t i o n s d e s t r o y i n g 90 to 95% of the eggs and l a r v a e produced d u r i n g the f i r s t and second generat- i o n s (Hughes, 1959). About t w o - t h i r d s of the m o r t a l i t y occurs i n the egg stage and the fewest eggs s u r v i v e d when catches of B. lampros were g r e a t e s t (Coaker, 1965). Wright e t a l . (1960), i n experiments u s i n g crops exposed to the f i r s t g e n e r a t i o n of the p e s t , showed t h a t p r e d a t o r y b e e t l e s c o u l d markedly reduce cabbage r o o t f l y numbers and consequently crop damage. They demonstrated t h a t the numbers of the p r i n c i p a l p r e d ator trapped, B. lampros, were i n v e r s e l y r e l a t e d t o the numbers of s u r v i v i n g r o o t f l y eggs and l a r v a e . Coaker (1965) used b a r r i e r s to r e s t r i c t the movement of a d u l t c a r a b i d s i n t o and out of p l o t s of b r a s s i c a crops and a l s o found t h a t the s u r v i v a l of the immature stages of the cabbage r o o t f l y was i n v e r s e l y r e l a t e d to the p o p u l a t i o n l e v e l of the p r e d atory c a r a b i d s . A f t e r e x c l u d i n g a d u l t c a r a b i d s almost e n t i r e l y from the p l o t s , he estimated t h a t they had been 7. r e s p o n s i b l e f o r up to o n e - t h i r d o f the t o t a l egg m o r t a l i t y , although t h i s v a r i e d w i t h the s p e c i e s composition of the c a r a b i d p o p u l a t i o n . Van D i n t h e r and Mensink (1971) s t u d i e d the r o l e t h a t c a r a b i d b e e t l e s p l a y as p r e d a t o r s of the cabbage r o o t f l y , u s i n g house 32 f l y eggs l a b e l l e d w i t h P and exposed under f i e l d c o n d i t i o n s . L a b e l l e d eggs were then used t o d e t e c t those s p e c i e s out o f the many pr e d a t o r s encountered i n the f i e l d , t h a t are predacious on eggs. They found t h a t among the c a r a b i d s B. lampros, B. ustulatum and B. femoraturn were the most important egg-feeders. 8. 2.2 Cabbage maggot, Hylemya b r a s s i c a e (Bouch6) ( D i p t e r a : Anthomyiidae) T h i s i n s e c t i s c a l l e d the cabbage r o o t f l y i n the U.K. (Anon., 1947) and the cabbage maggot i n North America (Muesebeck, 1942). Although the s p e c i f i c name, b r a s s i c a e has been g e n e r a l l y accepted, the g e n e r i c name has not and t h e r e are a t p r e s e n t f i v e i n r e g u l a r use. Hylemya i s used by workers i n the U n i t e d S t a t e s and Canada. French (Missonier and S t e n g e l , 1966), German ( E n d r i g k e i t , 1953) and Russian (Ageeva, 1965) authors used C h o r t o p h i l a w h i l e o t h e r s use Phorbia ( R i e d e l , 1967), Hylemyia (Rygg, 1962; V a r i s , 1958) or D e l i a (Berte e t a l . , 1965). In the U.K. D e l i a has been superseded by E r i o i s c h i a (Kloet and Hincks, 1945) and the p e s t i s d e s i g n a t e d as E r i o i s c h i a b r a s s i c a e (Bouch<*=) . T h i s i n s e c t has been a d e s t r i c t i v e p e s t i n E a s t e r n Canada s i n c e about 1855. I t i s not known when the pest a r r i v e d i n B r i t i s h Columbia but by 1915 the pest had become w e l l e s t a b l i s h e d i n the p r o v i n c e ,'Gibson and Treherne (1916) . I t now occurs i n v e g e t a b l e growing areas throughout the country, i n c l u d i n g the North West T e r r i t o r i e s (Beirne, 1971). 2.2.1 Generation and l i f e c y c l e Depending on c l i m a t i c c o n d i t i o n s , t h i s i n s e c t may have one g e n e r a t i o n per year i n the n o r t h e r n U.S.S.R. (Danilevsky, 1961) or f o u r or f i v e i n some p a r t s o f the U.S.A. (Carlson e t a l . , 1947). In Canada, the number of g e n e r a t i o n s ranges from one complete wi t h a p a r t i a l second i n Newfoundland to t h r e e i n south western O n t a r i o and southern B r i t i s h Columbia (Caesar, 1922; M u k e r j i and Harcourt, 1970; Forbes, 1962). Smith (1927) used the term 9. ge n e r a t i o n t o d e s c r i b e the c y c l e s t a r t i n g a t the a d u l t and ending a t the pupa. Other workers ( M i l e s , 1954; Hughes and S a l t e r , 1959) have used i t to d e s c r i b e the c y c l e s t a r t i n g from the egg and ending w i t h the a d u l t . A d u l t s of the f i r s t g e n e r a t i o n emerge i n l a t e A p r i l and e a r l y May from the overwintered pupae. A f t e r a p r e - o v i p o s i t i o n p e r i o d o f 6 to 8 days the females begin to l a y eggs s i n g l y , i n c r e v i c e s i n the s o i l and on the underside of s o i l crumbs u s u a l l y w i t h i n 5 cm of the host p l a n t (Hughes and S a l t e r , 1959). Eggs are l a i d c h i e f l y around the stems of c r u c i f e r o u s p l a n t s but under some c o n d i t i o n s , they are l a i d on the heads of c a u l i f l o w e r s (Smith, 1927) and on B r u s s e l s sprouts (Brooks, 1951; Coaker, 1967). The eggs hatch w i t h i n a week i n the f i e l d and the l a r v a e move immediately to the p l a n t roots' to feed. At the end of a 3 to 4 week i n t e n s i v e l a r v a l f e e d i n g p e r i o d , t h i r d - i n s t a r l a r v a e move away from the r o o t s to pupate i n the s o i l . The next gen- e r a t i o n of a d u l t s emerges from these p u p a r i a w i t h i n two weeks, prov i d e d t h a t there has been no i n d u c t i o n of pupal a e s t i v a t i o n ( M i s s o n i e r , 1960) or diapause (Hughes and S a l t e r , 1959; Zabirov, 1961). 10. 2.2.2 C o n t r o l C u l t u r a l These methods i n c l u d e crop r o t a t i o n , the d e s t r u c t i o n of i n f e s t e d p l a n t s , a v o i d i n g growing autumn crops of host p l a n t s t h a t encourage l a r g e o v e r w i n t e r i n g p o p u l a t i o n s of cabbage r o o t f l y , and growing seed crops away from main b r a s s i c a areas (Schoene, 1916; Bonnemaison, 1965). Most of f i r s t - g e n e r a t i o n f l i e s feed o n l y on the n e c t a r of hedgerow f l o w e r s . Removal of these f l o w e r s from the v i c i n i t y of the host crop may t h e r e f o r e o f f e r a p o s s i b l e method of c o n t r o l l i n g cabbage r o o t f l y (Coaker and F i n c h , 1971). F i n c h and Skinner (1971) found t h a t removing hedgerow s i t e s from w i t h i n 40, 80 or 160 m of p l o t s of b r a s s i c a s , f a i l e d t o reduce p o p u l a t i o n s of the cabbage r o o t f l y . P l a n t r e s i s t a n c e R e s i s t a n c e has been r e p o r t e d among the host p l a n t s of the cabbage r o o t f l y (Pimentel, 1961; Beck, 1965). P l a n t s can be r e s i s t a n t because they are not a t t r a c t i v e t o o v i p o s i t i n g a d u l t s ( R a d c l i f f e and Chapman, 1960; Doane and Chapman, 1962), or because they are capable of t o l e r a t i n g and outgrowing damage when a t t a c k e d (Matthewman and L y a l l , 1966). Doane and Chapman (1962) r e p o r t e d t h a t the cabbage r o o t f l y l a i d eggs on rutabagas and t u r n i p s i n p r e f e r e n c e to r a d i s h or mustard, c a u l i f l o w e r being the l e a s t p r e f e r r e d of the crops t e s t e d . In New Brunswick, y i e l d s of v a r i e t i e s r e s i s t a n t to cabbage r o o t f l y were 30 to 50% higher than s u s c e p t i b l e v a r i e t i e s ; but the v a r i e t i e s r e s i s t a n t to cabbage r o o t f l y were more a t t r a c t i v e to bean-seed f l y (Pond et a l . , 1962). Swailes (1960) found t h a t r e s i s t a n c e c o u l d r e s u l t 11. e i t h e r because l a r v a e encounter d i f f i c u l t i e s i n becoming e s t a b l i s h e d or because the n u t r i t i v e q u a l i t i e s of the r o o t s are u n s u i t a b l e f o r l a r v a l growth. I n s e c t i c i d e I t was not u n t i l i n t r o d u c t i o n of the c y c l o d i e n e . group of o r g a n o c h l o r i n e i n s e c t i c i d e s , which were h i g h l y potent and per- s i s t e n t i n the s o i l , t h a t t r u l y p r a c t i c a l and r e l i a b l e c o n t r o l of cabbage r o o t f l y was achieved (Wright, 1954). These compounds were a p p l i e d e i t h e r t o the s o i l or t o the p l a n t r o o t s b e f o r e or a f t e r sowing or p l a n t i n g , or to the f o l i a g e (Forbes and King, 1956; Bonnemaison, 1965). The t o x i c i t y o f o r g a n o c h l o r i n e i n s e c t i c i d e s t o n a t u r a l enemies of cabbage r o o t f l y (Morris, 1960; Chapman and Eckenrode, 1973), and the development of r e s i s t a n c e by t h i s p e s t t o c y c l o d i e n e compounds i n North America ( F i n l a y s o n , 1962; H a r r i s e t a_l. , 1962; Howitt and c o l e , 1962; McEwen et_ a l . , 1967), and i n England (Coaker e t al_. , 1963), S c o t l a n d (Osborne, 1968), Norway (Taksdal and Nordby, 1966), Sweden ( H e l i q u i s t , 1964) and France (Missonier e t a l . , 1964) have l e d to the use of other i n s e c t i c i d e s . In Canada and elsewhere a l t e r n a t i v e i n s e c t i c i d e s have been' found among the organophosphorus and'carbamate compounds (Coaker and F i n c h , 1964; F i n l a y s o n and Noble, 1964; F i n l a y s o n , e t a l . , 1967; Judge e t a l . , 1968; R o l f e , 1969) (Appendix Ta b l e 11). Of the organophosphorus i n s e c t i c i d e s t e s t e d i n the f i e l d , c h l o r f e n v i n p h o s , f e n s u l f o t h i o n , d i a z i n o n and t h i o n a z i n , the l e a s t e f f e c t i v e was d i a z i n o n . Carbofuran, an organocarbamate had 12. systemic properties (Finlayson, 1969). Similar r e s u l t s have been obtained by Morris (1968) and Read (1970). Finlayson and Campbell (1969) found that s p l i t applications, one at seeding and one at 30 days l a t e r with chlorfenvinphos, fensulfothion or carbofuran protected cauliflowers from damage u n t i l harvest. Hertveldt- a l . (197 3) i n t h e i r experiments on chemical control of cabbage root f l y i n transplanted Brussels sprouts found that chlorfenvinphos i n wettable powder retained a high degree of effectiveness for at l e a s t 12 weeks when the i n s e c t i - cide was applied around the base of the transplants at a rate of 100 mg active ingredient per plant. I t has become more d i f f i c u l t i n recent years to achieve acceptable lev e l s of control of a number of important pests of vegetables than was the case ten years ago (Gair, 1971; Wright, 1971). There i s a strong tendency to blame the present problems on the inadequacies of the new types of chemicals which do not have the persistence for single applications to protect crops throughout t h e i r growing season. The very c h a r a c t e r i s t i c of persistence, which so favoured the performance of the organo- chlorine compounds, was the p r i n c i p a l reason for t h e i r downfall (Wheatley, 1971). Some r e l a t i v e l y stable organophosphorus compounds, such as chlorfenvinphos or fonofos, are perhaps one- half to o n e - f i f t h as persistent i n s o i l as gamma-BHC, which i s one of the l e a s t persistent organochlorines (Wheatley, 1971). The i d e a l l y s e l e c t i v e chlorfenvinphos, which i s probably the best present-day al t e r n a t i v e , i s less e f f e c t i v e than were the o r g a n o c h l o r i n e s , d e s p i t e the l a r g e n a t u r a l enemy-induced m o r t a l i t y t h a t the use of c h l o r f e n v i n p h o s permits (Mowat and Coaker, 1967). N e v e r t h e l e s s , i f a h i g h l e v e l of c o n t r o l ' i s o b t a i n e d d u r i n g the f i r s t few weeks a f t e r p l a n t i n g , the crops become w e l l e s t a b l i s h e d and can then withstand i n j u r y without s e r i o u s r e d u c t i o n i n y i e l d , (Coaker, 1969). N a t u r a l The immature stages of the cabbage r o o t f l y are food f o r many arthropods (Wishart e t a l . , 1956; de Wilde, 1947; Abu Yaman, 1960; Coaker, 1965). Many hymenopterous p a r a s i t e s of the cabbage r o o t f l y a t t a c k the l a r v a l stages but o n l y k i l l the i n s e c t a f t e r pupation. F i v e s p e c i e s of Braconidae, t h r e e of C y n i p i d a e and f o u r of Ichneumonidae have been re a r e d from cabbage r o o t f l y pupae (Wishart e t a l . , 1957; Hughes and S a l t e r , 1959). The c y n i p i d Idiomorpha rapae (Westw.) which l a y s i t s eggs on the f i r s t or second-stage l a r v a e , i s the o n l y hymenopterous p a r a s i t e of major importance (Wishart e t a l . , 1957). Species of A l e o c h a r a ( C o l e o p t e r a : S t a p h y l i n i d a e ) are known to p a r a s i t i z e 20 to 30% of cabbage r o o t f l y pupae (Read, 1962; Coaker, 1966). Coaker and W i l l i a m s (1963) have shown t h a t a d u l t c a r a b i d b e e t l e s were r e s p o n s i b l e f o r about o n e - t h i r d of the egg m o r t a l i t y and the remaining egg m o r t a l i t y was due mostly to p r e d a t i o n by a d u l t s t a p h y l i n i d b e e t l e s . The c a r a b i d s t h a t were found to be most important i n c l u d e d : B. lampros and Harpalus aeneus (Fab) which were predominant d u r i n g A p r i l and May; and F e r o n i a m e l a naria (111.) (= P. m e l a n a r i u s ) , Harpalus r u f i p e s (Deg.) and Trechus q u a d r i s t r i a t u s (Schrank), which became important i n 14. J u l y (Coaker and W i l l i a m s , 1963; M i t c h e l l , 1963a). An a n a l y s i s of the p o p u l a t i o n dynamics of the cabbage r o o t f l y i n England (Hughes and M i t c h e l l , 1960) showed t h a t no s i n g l e m o r t a l i t y f a c t o r was r e s p o n s i b l e f o r m a i n t a i n i n g the remarkably c o n s t a n t number of a d u l t s t h a t o c c u r r e d from one g e n e r a t i o n t o the next. Only the d i r e c t r e l a t i o n s h i p between the numbers of f e e d i n g l a r v a e and the p r o p o r t i o n of p l a n t s k i l l e d c o u l d p o s s i b l y account f o r t h i s r e g u l a t i o n . . In a s i m i l a r analysis,---Mukerji (1971) showed t h a t "misadventure" of young l a r v a e i s the key f a c t o r a f f e c t i n g s u r v i v a l i n Canada. Benson (1973) r e - a n a l y z e d the l i f e - t a b l e s f o r cabbage r o o t f l y popu- l a t i o n s i n Canada (Mukerji, 19 71) and England (Hughes and M i t c h e l l , 1960). He showed t h a t the k e y - f a c t o r determining p o p u l a t i o n change i n Canada i s caused by f a i l u r e of the observed , a d u l t females t o achieve t h e i r p o t e n t i a l egg p r o d u c t i o n . T h i s o n l y occurs a t the begi n n i n g of the second g e n e r a t i o n each year. In England the k e y - f a c t o r i s probably egg p r e d a t i o n . 15. 2.3 O t h e r m a j o r p e s t s o f b r a s s i c a s ( A p h i d s and L e p i d o p t e r a ) B r a s s i c a c r o p s a r e a l s o a t t a c k e d b y o t h e r p e s t s o f e c o n o m i c i m p o r t a n c e b e s i d e s t h e cab b a g e r o o t f l y . T h e s e i n c l u d e t h e ca b b a g e a p h i d , B r e v i c o r y n e b r a s s i c a e ( L i n n a e u s ) ; g r e e n p e a c h a p h i d , Myzus p e r s i c a e ( S u l z e r ) ; i m p o r t e d c a b b a g e worm, P i e r i s r a p a e ( L i n n a e u s ) ; diamond-back moth, P l u t e l l a m a c u l i p e n n i s ( C u r t i s ) ; and c a b b a g e l o o p e r , T r i c h o p l u s i a n i (Hubner) ( F o r b e s and M a c C a r t h y , 1959; Banham and A r r a n d , 1 9 7 0 ) . 2.3.1 E f f e c t i v e n e s s o f methomyl on a p h i d s and l e p i d o p t e r a The c a r b a m a t e i n s e c t i c i d e , methomyl ( L a n n a t e ) S - m e t h y l - N - [ ( m e t h y l c a r b a m o y l ) - o x y ] t h i o a c e t i m i d a t e , f o r m u l a t e d a s a w a t e r - d i s p e r s i b l e powder i s e f f e c t i v e as a f o l i a r s p r a y a g a i n s t a w i d e s p e c t r u m o f p e s t s s u c h as c a b b a g e l o o p e r s , c a b b a g e worm, diamond- bac k moth, c o r n earworm, s o u t h e r n armyworm, t o b a c c o budworm, a p h i d s , l e a f h o p p e r s and c e r t a i n b e e t l e s ( C r e i g h t o n e t a l . , 1971; G r e e n and Workman, 1971). Methomyl has a s h o r t r e s i d u a l e f f e c t and i t i s r e a d i l y m e t a b o l i z e d by c o r n and c a b b a g e p l a n t s i n t o h a r m l e s s p r o d u c t s l i k e a c e t o n i t r i l e , c a r b o n d i o x i d e , and m e t h y l - amine w h i c h a r e r e i n c o r p o r a t e d i n t h e p l a n t t i s s u e s a s c a r b o h y d r a t e s o r l i p i d s ( H i l l , 1970; H a r v e y , 1 9 7 1 ) . B u t t h e i n s e c t i c i d e i s m o d e r a t e l y p e r s i s t e n t i n s o i l , f r o m 50 t o 75% r e m a i n i n g 30 d a y s a f t e r a p p l i c a t i o n ( H i l l , 1 9 7 0 ). 2.3.2. E f f e c t i v e n e s s o f B a c i l l u s t h u r i n g i e n s i s . B e r l i n e r on l e p i d o p t e r a B a c i l l u s t h u r i n g i e n s i s B e r l i n e r has been used a g a i n s t the imported cabbage worm, the cabbage looper and the diamond-back moth, by i t s e l f or wit h a chemical i n s e c t i c i d e . The b a c t e r i a remain a c t i v e from f i v e to ten days (Tanada, 1956; Fox and Jacques, 1961). T e s t s by McEwen and Harvey (1959) showed t h a t good c o n t r o l of the imported cabbage worm c o u l d be obtained w i t h B. thurin^..'. g i e n s i s spore dust a p p l i e d a t a r a t e of 0.3 l b s / a c r e a t a con- c e n t r a t i o n o f 10^ spores/g. C r e i g h t o n e t a l . (1971) compared B. t h u r i n g i e n s i s w i t h chemical i n s e c t i c i d e s . D i p e l , a commercial f o r m u l a t i o n of B. t h u r i n g i e n s i s , was the most e f f e c t i v e of fou r t e s t e d . I t was s u p e r i o r to c o n v e n t i o n a l sprays of methomyl and endosulfan p l u s p a r a t h i o n i n p r o t e c t i n g cabbage p l a n t s . There has been much documented evidence t h a t B. t h u r i n g i e n s i s does not d i r e c t l y d e s t r o y p a r a s i t e s and p r e d a t o r s (Jacques, 1965; F a l c o n e t a l . , 1968). With the c u r r e n t i n t e r e s t i n p r e v e n t i n g environmental contamination and the need to develop i n t e g r a t e d c o n t r o l and pes t management programs, B. t h u r i n g i e n s i s i s one of the few a v a i l a b l e s e l e c t i v e and e c o l o g i c a l l y s a f e , i n s e c t c o n t r o l agents (Falcon, 1971). 17. 2.4 T o x i c i t y of i n s e c t i c i d e s to n a t u r a l enemies of cabbage r o o t f l y 2.4.1 D i r e c t e f f e c t s of i n s e c t i c i d e s The m o r t a l i t y caused d i r e c t l y by c o n t a c t of a n a t u r a l enemy with a t o x i c a n t has been abundantly documented i n terms of the r e d u c t i o n s i n t h e i r numbers or i n the degree of p a r a s i t i s m or p r e d a t i o n which f o l l o w e d i n s e c t i c i d e a p p l i c a t i o n s i n the f i e l d . S ince one or more stages of a n a t u r a l enemy must a c t i v e l y search out prey or h o s t s , i t i s reasonable to expect t h a t p r e d a t o r s and p a r a s i t e s would p i c k up g r e a t e r amounts of t o x i c a n t and thus s u f f e r g r e a t e r m o r t a l i t y from r e s i d u a l d e p o s i t s than would the more sedentary p e s t s occupying the same h a b i t a t ( C r o f t and Brown, 1975). There i s c o n s i d e r a b l e evidence which suggest t h a t i n s e c t i - c i d e s , p a r t i c u l a r l y c y c l o d i e n e s , when a p p l i e d to s o i l as a p r o t e c t i o n a g a i n s t r o o t maggots i n a d v e r t e n t l y d e s t r o y l a r g e numbers o f p r e d a t o r s and p a r a s i t e s r e s u l t i n g , i n some cases, i n more severe i n f e s t a t i o n and subsequent damage (Mo r r i s , 1960; Read, 1960, 1964; Mowat, 196 4; Coaker, 196 6; Mowat and Coaker, 1967)). Hassan (1969) s t u d i e d the e f f e c t s of organophosphorus (OP) i n s e c t i c i d e s on c a r a b i d and s t a p h y l i n i d b e e t l e s d u r i n g the egg stage of the cabbage r o o t f l y u s i n g d i a z i n o n and c h l o r f e n - vinphos granules a p p l i e d around the base of cabbage t r a n s p l a n t s . The r e s u l t s showed t h a t d i a z i n o n treatments reduced s i g n i f i c a n t l y the number of c a r a b i d and s t a p h y l i n i d p r e d a t o r s i n the p l o t s f o r about ele v e n weeks. The c a r a b i d s were found to be remarkably t o l e r a n t to c h l o r f e n v i n p h o s . 18. Edwards and Thompson (175) a s s e s s e d t h e e f f e c t s on c a r a - b i d p r e d a t o r s o f some a g r i c u l t u r a l s o i l i n s e c t i c i d e s and c o n - c l u d e d t h a t among t h o s e t e s t e d , f o n o f o s , p a r a t h i o n and p h o r a t e were e x t r e m e l y t o x i c . The b e e t l e s were p r o b a b l y k i l l e d by t h e stomach a c t i o n o f t h e i n s e c t i c i d e when th e y f e d on l e a f t i s s u e s and a l s o , but l e s s l i k e l y , on p r e y c o n t a i n i n g t h i s i n s e c t i c i d e s i n c e i t i s well-known t h a t many s p e c i e s o f c a r a b i d s and s t a p h y l i n i d s a r e not e x c l u s i v e l y predaceous. and c a r n i v o r o u s but w i l l f e e d on p l a n t t i s s u e s . A l a b o r a t o r y s t u d y o f t h e e f f e c t s o f some s o i l - a p p l i e d OP p e s t i c i d e s on c a r a b i d b e e t l e s showed t h a t h i g h e r s o i l m o i s t u r e i n c r e a s e d t h e speed o f k i l l i n s o i l t r e a t e d w i t h t h i o n a z i n ( C r i t c h l e y , 1972a). I n a s i m i l a r f i e l d i n v e s t i g a t i o n , C r i t c h l e y (1972b) found t h a t s p e c i e s o f C a r a b i d a e a f f e c t e d most by t h e t r e a t m e n t s were s m a l l , d i u r n a l l y a c t i v e s p e c i e s such as Bembidion lampros ( H b s t . ) , B. quadrimaculatum (L.) and Trechus q u a d r i s t r i a t u s ( S c h r . ) , w h i c h were abundant a t t h e time when t h e t r e a t m e n t was a p p l i e d . L a r g e s p e c i e s such as H a r p a l u s r u f i p e s (deg.), P t e r o s t i c h u s v u l g a r i s ( L . ) , P. madidus (F.) and C a l a t h u s f u s c i p e s (Goeze) were a l s o a f f e c t e d but were g e n e r a l l y l e s s s u s c e p t i b l e , p a r t l y because t h e y appeared l a t e r i n t h e season when some o f t h e p e s t i c i d e had d i s a p p e a r e d . B a r t l e t t (1964) has g e n e r a l i z e d t h a t i t i s i n t h e a d u l t s t a g e s t h a t p r e d a t o r s a r e most s u s c e p t i b l e t o i n s e c t i c i d e s , and eggs l e a s t a f f e c t e d . 2.4.2 I n d i r e c t e f f e c t s of i n s e c t i c i d e s P e s t i c i d e s can a f f e c t p r e d a t o r s and p a r a s i t e s i n d i r e c t l y through t h e i r i n f l u e n c e on the pe s t s p e c i e s which c o n s t i t u t e t h e i r prey or t h e i r h o s t s , e i t h e r by e l i m i n a t i n g these as a source of food or by l e a v i n g them as sources of secondary p o i s o n i n g ( C r o f t and Brown, 1975). There are numerous reviews which r e l a t e to pest resurgence, r e s u l t i n g from the sequence of pest e l i m i n a t i o n , s t a r v a t i o n among the remaining n a t u r a l enemies, and pest r e i n v a s i o n b e f o r e the n a t u r a l enemies are r e - e s t a b l i s h e d (Ripper, 1956; S t e r n e t a l . , 1 9 5 9 ; Van den Bosch and S t e r n , 1962)* The e f f e c t s of s u b l e t h a l doses of i n s e c t i c i d e s a t l e v e l s which cause no m o r t a l i t y i n the p o p u l a t i o n or a t t o x i c l e v e l s which leave some s u r v i v o r s , have been reviewed by M o r i a r t y (1969). Coaker (1966) r e p o r t e d t h a t a n o n - s e l e c t i v e i n s e c t i c i d e , p resent a t c o n c e n t r a t i o n s too low to c o n t r o l the cabbage r o o t f l y , can i n c r e a s e damage by r e d u c i n g p o p u l a t i o n s of i t s n a t u r a l enemies, p a r t i c u l a r l y p r e d a t o r y b e e t l e s . The a c t i v i t y o f c a r a - b i d b e e t l e s i s g r e a t l y i n c r e a s e d by the OC i n s e c t i c i d e s a l d r i n , d i e l d r i n and DDT and by c e r t a i n OP compounds, e.g. t h i o n a z i n (Coaker, 1966; Dempster, 1968; Edwards e t a l . , 1970; C r i t c h l e y , 1972a). With B. lampros t h i s b e h a v i o u r a l response r e s u l t e d i n i n c r e a s e d catches i n p i t f a l l t r a p s (Coaker, 1966). Harpalus aeneus (= H. a f f i n i s ) when exposed to s u b l e t h a l l e v e l s of i n s e c t i c i d e s responds by r e l e a s i n g l a r g e amounts of a chem i c a l , probably formic a c i d , which might be s u f f i c i e n t t o cause s e l f - a n n i h i l a t i o n i n the c o n f i n e s of i t s burrows ( C r i t c h l e y , 1972a) A d u l t H. r u f i p e s when exposed to s u b l e t h a l d e p o s i t s o f DDT had a reduced f e e d i n g r a t e which may prevent the pr e d a t o r from c o n t r o l l i n g P i e r i s rapae f o r some time a f t e r spray treatments (Dempster, 1968). 2.5 Pr o s p e c t s f o r i n t e g r a t e d c o n t r o l of b r a s s i c a p e s t s The concept of i n t e g r a t e d c o n t r o l i m p l i e s t h a t chemical treatments be used with minimal harm to pr e d a t o r y b e e t l e s (Edwards and Thompson, 1975). With r e c e n t r e s t r i c t i o n s p l a c e d on OC i n s e c t i c i d e s , growers have l o s t some of t h e i r most e f f e c t i v e p e s t c o n t r o l s . 2.5.1 S e l e c t i v i t y i n i n s e c t i c i d e s Expansion of i n t e g r a t e d c o n t r o l programs i s l i m i t e d i n p a r t by the nature of a v a i l a b l e c o n t r o l m a t e r i a l s . I t has been s a i d t h a t the i d e a l s e l e c t i v e treatment i s not n e c e s s a r i l y one t h a t e l i m i n a t e s a l l i n d i v i d u a l s of the pe s t s p e c i e s w h i l e l e a v i n g a l l of the n a t u r a l enemies (Clausen, 1956; Ripper, 1956; S t e r n e t a l . , 1959). Use o f such a m a t e r i a l would f o r c e the p r e d a t o r s and p a r a s i t e s to leave the t r e a t e d area or s t a r v e . Wright (1956) n o t i c e d t h a t p l o t s where DDT, a l d r i n , or BHC had been used by i n c o r p o r a t i o n i n t o the top 9 cm of s o i l , s u s t a i n e d more damage from cabbage r o o t f l y l a r v a e than those u n t r e a t e d . Root and s o i l samples r e v e a l e d l a r g e r numbers of cabbage r o o t f l y l a r v a e and pupae on t r e a t e d than u n t r e a t e d p l o t s ; a p p a r e n t l y the i n s e c t i c i d e s were s e l e c t i v e l y more t o x i c t o cabbage r o o t f l y p r e d a t o r s than t o the cabbage r o o t f l y i t s e l f thus r e s u l t i n g i n more damage to the cabbage crop. In a f i e l d study of the e f f e c t i v e n e s s of c e r t a i n i n s e c t i - c i d e s i n c o n t r o l l i n g the cabbage r o o t f l y and the harm they may cause to p a r a s i t e s , Hassan (1973) found t h a t c h l o r f e n v i n p h o s gave the be s t p r o t e c t i o n f o l l o w e d by bromophos, d i a z i n o n , dimethoate, P a r a t h i o n - e t h y l and l i n d a n e i n order of d i m i n i s h i n g e f f e c t i v e n e s s . In s i m i l a r s t u d i e s , Mowat (1966) compared the t o x i c i t y of d i e l d r i n , an OC, with t h a t of f o u r OP i n s e c t i c i d e s , to ground b e e t l e s which prey on immature stages of the r o o t f l y . In medium sandy loam, the most t o x i c was t h i o n a z i n . C h l o r f e n v i n p h o s was of v e r y low t o x i c i t y as were a l s o azinphos- methyl and, i n dry s o i l d i a z i n o n . F i n l a y s o n e t a l . (1975) a l s o found t h a t the i n s e c t i c i d e s isophenphos, c a r b o f u r a n , c h l o r f e n - vinphos and f e n s u l f o t h i o n d i d not a f f e c t the p o p u l a t i o n s of p r e d a t o r y b e e t l e s . However, the numbers of earthworms were g r e a t l y reduced by c a r b o f u r a n and to a l e s s e r degree by c h l o r - fenvinphos. Edwards and Thompson (1975) concluded t h a t c h l o r f e n v i n p h o s tends to be more t o x i c to d i p t e r a n s than t o other k i n d s o f i n s e c t s and i s thus one of the b e s t i n s e c t i c i d e s f o r r e d u c i n g cabbage r o o t f l y and wheat b u l b f l y . I t s success, they added, may be due not o n l y to i t s t o x i c i t y to the p e s t , but a l s o i n p a r t to i t s l a c k of t o x i c i t y t o the p r e d a t o r s or even c o n c e i v a b l y to i n c r e a s i n g t h e i r a c t i v i t y and f e e d i n g . The r e s u l t s of t e s t s on cabbage r o o t f l y c o n t r o l , i n s e v e r a l a r e a s , i n d i c a t e t h a t a number of compounds p r o v i d e good c o n t r o l of the pest. D e c i s i o n s to be made i n v o l v e a) compounds to use f o r d i f f e r e n t c r u c i f e r o u s crops and b) methods of a p p l i c a t i o n . For rutabagas, a p e r s i s t e n t compound t h a t w i l l g i v e long term p r o t e c t i o n i s r e q u i r e d (Read, 1970). For stem c r u c i f e r s , h i g h l y e f f e c t i v e c o n t r o l i s r e q u i r e d o n l y when the p l a n t s are s m a l l . When the stems become l a r g e and woody i n t e x t u r e , they can. be q u i t e s e v e r e l y i n f e s t e d without much e f f e c t on y i e l d . Thus long term c o n t r o l i s not r e q u i r e d (Coaker and F i n c h , 1965; Coaker, 1969; Read, 1970). 2.5.2 Mode of a p p l i c a t i o n One of the most important c o n s i d e r a t i o n s i s the degree of c o n t r o l o b t a i n e d w i t h v a r i o u s i n s e c t i c i d e s p l a c e d i n the row by d i f f e r e n t methods of a p p l i c a t i o n . Furrow treatments wi t h g r a n u l a r or l i q u i d f o r m u l a t i o n s of many m a t e r i a l s p l a c e d with or near the seed are o f t e n p h y t o t o x i c , except a t v e r y low r a t e s which are u s u a l l y i n e f f e c t i v e (McEwen et a l . , 1967). Narrow-band placements of e f f e c t i v e g r a n u l a r i n s e c t i c i d e s f r e q u e n t l y reduce the p l a n t stand, which i n t u r n can i n c r e a s e maggot f e e d i n g i n j u r y on i n d i v i d u a l r o o t s (Eckenrode and Chapman, 1971). I n s e c t i c i d e s when broadcast, have d e t r i - mental e f f e c t s on n a t u r a l p r e d a t o r s of the cabbage r o o t f l y ( P i t r e and Chapman,. 1964) . The r o o t maggots have o n l y l i m i t e d c o n t a c t w i t h the s o i l as they move down between the p l a n t stem and the s o i l t o begin f e e d i n g i n the r o o t s o f the host p l a n t (Read, 1964). Chapman and Eckenrode (1973) s t u d i e d the e f f e c t s of i n s e c t i c i d e placement on predator numbers and cabbage maggot c o n t r o l . They found t h a t as bands of g r a n u l a r i n s e c t i c i d e s were moved away from the seed furrow, p h y t o t o x i c i t y and c o n t r o l of cabbage maggot decreased and more p r e d a t o r y b e e t l e s s u r v i v e d . Consequently, w i t h b r o a d c a s t a p p l i c a t i o n s , g r e a t e r maggot-feeding damage o c c u r r e d when m a t e r i a l s were used which were i n e f f i c i e n t (diazinon) or to which the maggot was 24. r e s i s t a n t ( a l d r i n ) , than i f the crop had been l e f t u n t r e a t e d . One method of c o n t r o l i s t o band the g r a n u l a r i n s e c t i c i d e on the s o i l s u r f a c e , i n c o r p o r a t e t o a depth of about 2.5 cm and then seed i n the c e n t r e of the band of i n s e c t i c i d e . Such treatments are u s u a l l y f o l l o w e d by one or more spray-band or drench a p p l i c a t i o n s a p p l i e d d u r i n g the season, as recommended by F i n l a y s o n and Noble (1966) and M o r r i s (1968). The drench treatments are r e q u i r e d because the s i n g l e p r e p l a n t i n g t r e a t - ment a t a low r a t e i s i n s u f f i c i e n t to g i v e p r o t e c t i o n through- out the growing season but w i l l not a f f e c t the n a t u r a l enemies and t h e r e w i l l be no h i g h r e s i d u e s l e f t i n the s o i l or the p l a n t s a t h a r v e s t . Conversely, Read (1970) recommended the use of a s u r f a c e band a p p l i c a t i o n a p p l i e d a t a h i g h r a t e t h a t would g i v e a l l - season c o n t r o l of the p e s t w i t h a s i n g l e p r e p l a n t i n g a p p l i c a t i o n . He argued t h a t subsurface a p p l i c a t i o n s are l e s s harmful to a d u l t p r e d a t o r y b e e t l e s , more economical i n terms of labour s i n c e the treatment i s a p p l i e d once, and are p r o t e c t e d from d i s p e r s a l by r a i n and from d r y i n g out (Osborne, 1968). 3. MATERIALS AND METHODS 3.1 D e s c r i p t i o n o f s i t e and pretreatment c u l t i v a t i o n The experiments were undertaken a t the South campus o f the U n i v e r s i t y of B r i t i s h Columbia, Vancouver i n the s p r i n g and summer o f 197 5. S o i l a t the s i t e was a sandy loam con- t a i n i n g many l a r g e stones. The f i e l d , f r e e from i n s e c t i c i d e r e s i d u e s , was 16 m x 20 m, i n an area where b r a s s i c a s had never been grown. P r i o r t o treatment, the f i e l d was harrowed once and most of the l a r g e r stones removed. 3.2 Crop and l a y o u t of f i e l d The experiments were c a r r i e d out u s i n g one v a r i e t y o f B r u s s e l s s p r o u t s , the e a r l y h y b r i d v a r i e t y , Jade C r o s s . The B r u s s e l s sprouts were seeded i n the greenhouse on 30/1/1975 and t r a n s p l a n t e d i n the f i e l d on 10/4/1975. Spacing between the rows was 0.66 m and between p l a n t s was 0.5 m. Experimental p l o t s w i t h i n the f i e l d were 4 x 4 m and were arranged i n fo u r randomized iblocks each p l o t c o n t a i n i n g 30 p l a n t s i n 5 rows of 6 p l a n t s . A t the time the f i e l d was l a i d out, i t was surrounded by a b a r r i e r of polythene s h e e t i n g ( p o l y e t h y l e n e , 4 mil) extending about 10 cm below the s o i l s u r f a c e and 15 cm above where i t was f a s t e n e d t o wooden stakes. S i m i l a r l y , p l o t s w i t h i n the f i e l d were separated from one another by polythene b a r r i e r s ( F i g . 1). The o u t e r b a r r i e r surrounding the f i e l d was t o prevent p r e d a t o r y b e e t l e s from e n t e r i n g i t ; the b a r r i e r s s e p a r a t i n g the p l o t s were t o prevent p r e d a t o r y b e e t l e s and B. lampros i n p a r t i c u l a r from moving from one p l o t t o the other. The e f f e c t of the b a r r i e r s on numbers of pr e d a t o r y b e e t l e s w i t h i n the p l o t s was measured by p i t f a l l t r a p s i n each p l o t (Coaker, 1965). There were fo u r p i t f a l l t r a p s i n each o f the 20 p l o t s . Immediately o u t s i d e the b a r r i e r s surrounding the f i e l d twenty t r a p s were spaced a t equal d i s t a n c e s . The o u t s i d e t r a p s were t o h e l p determine the numbers and emergence of new s p e c i e s and the p o p u l a t i o n f l u c t u a t i o n s o f c a r a b i d s . The t r a p s were p l a c e d on 24/4/1975 as shown i n F i g . 2. The p i t f a l l t r a p s were made from new t i n cans, 7 cm i n diameter x 11 cm deep. A 2 cm hole was c u t i n the bottom and covered w i t h 40-mesh Lumite screen t o a l l o w r a i n water t o d r a i n w h i l e r e t a i n i n g the b e e t l e s ( F i n l a y s o n e t al_. , 1975) . The t i n cans were sunk i n the ground so t h a t the rims were f l u s h w i t h the s u r f a c e . A f t e r heavy r a i n the t r a p s were washed, d r i e d and r e p l a c e d i n the ground. 27. F i g u r e 1. Layout of experimental f i e l d showing some of the p l o t s , the polythene b a r r i e r s and B r u s s e l s sprout t r a n s p l a n t s a t the e a r l y stages. 27a. F i g u r e 2. P o s i t i o n of p i t f a l l t r a p s w i t h i n an experimental p l o t . 28a. 3.3 Design of experiment and treatments F i v e treatments, r e p l i c a t e d f o u r times i n a randomized b l o c k design were used to compare the damage caused and the s u r v i v a l of the r o o t - f l y eggs s u b j e c t e d to p r e d a t i o n by B. lampros; the treatments were a l s o used to determine the e f f e c t s of i n s e c t i c i d e s on the p o p u l a t i o n of B. lampros. The t r e a t - ments were: 1. C o n t r o l ; u n t r e a t e d w i t h i n s e c t i c i d e s and without B. lampros. 2. Untreated with i n s e c t i c i d e s but wi t h B. lampros. A l l other c a r a b i d s were excluded. 3. B a c i l l u s t h u r i n g i e n s i s B e r l i n e r ( D i p e l , 16000 IU/mg, at the recommended r a t e of 1 lb/100 gal/acre[1.12 Kg/ 1123 l i t r e / h a ] ) with B. lampros. A l l other c a r a b i d s were excluded. 4. Methomyl (Lannate a t the recommended r a t e of 1 l b / 100 gal/acre[1.12 Kg/1123 l i t r e / h a ] ) w i t h B. lampros. A l l other c a r a b i d s were excluded. 5. C h l o r f e n v i n p h o s ( B i r l a n e 10G a t the recommended r a t e of 1 oz/1000 f t of row [approx. 1 g/10 m]) with B. lampros. A l l other c a r a b i d s were excluded. 3.4 Release of r o o t f l y p u p a r i a For some time, b r a s s i c a s had not been c u l t i v a t e d near the s i t e o f the experiment. I t was t h e r e f o r e assumed t h a t the n a t u r a l p o p u l a t i o n of cabbage r o o t f l y i n the area would be low. In order t o have enough r o o t f l i e s t o work w i t h , about 2,00 0 p u p a r i a , r e a r e d at the Canada Department of A g r i c u l t u r e l a b o r a t o r y i n Vancouver ( F i g . 3) were b u r i e d i n shallow trenches around the f i e l d on May 1, 1975 t o g i v e an average of approximately three p u p a r i a per p l a n t . These were expected to emerge as a d u l t s w i t h i n 12 to 18 days l a t e r . F i g . 4 shows the stages i n the l i f e c y c l e of the cabbage r o o t f l y . 31. F i g u r e 3. Mass r e a r i n g of cabbage r o o t f l y f o r f i e l d r e l e a s e a t A g r i c u l t u r e Canada l a b o r a t o r y , Vancouver. 31a. 32. Figure 4. Stages i n the l i f e cycle of the cabbage root f l y , Hylemya brassicae (Bouch6). From top l e f t : eggs, larvae and puparium From bottom l e f t : male adult, female adult 32a. 3.5 I n t r o d u c t i o n and sampling of B. lampros p o p u l a t i o n The f i e l d was i n i t i a l l y sampled to determine the popula- t i o n o f B. lampros and other c a r a b i d s present a t the s t a r t of the experiment. Twenty B. lampros were added i n i t i a l l y t o each p l o t , except f o r p l o t s of treatment 1. The b e e t l e s had been captured from the experimental s u b - s t a t i o n a t Abbo t s f o r d , B.C. u s i n g p i t f a l l t r a p s . More were r e l e a s e d i n the p l o t s as they became a v a i l a b l e , f o r a t o t a l of 8 0 B. lampros per p l o t as f o l l o w s : D a t e No. of B. lampros r e l e a s e d per p l o t 1.5.75 20 6/5/75 1 0 13/5/75 20 19/5/75 20 28/5/75 1 0 The a d u l t c a r a b i d p o p u l a t i o n s on each p l o t were sampled every 2 days u s i n g four p i t f a l l t r a p s and the numbers recorded. C a r a b i d s , i n c l u d i n g B. lampros, trapped from treatment 1 were completely removed but B. lampros trapped from other t r e a t - ments were r e l e a s e d w i t h i n the p l o t s from which they o r i g i n a t e d a f t e r other c a r a b i d s had been removed. A l l t r a p s were emptied a t the same time each morning and the c a p t i v e s were r e t u r n e d to the p l o t s immediately a f t e r s o r t i n g . The t r a p s were cleaned and the surrounding s o i l smoothed d a i l y s i n c e the t r a p s q u i c k l y become i n e f f i c i e n t a f t e r heavy r a i n and d u r i n g hot d r y weather when the s o i l would crack away from the t r a p rim. Only c a r a b i d s known to feed on the immature stages of the cabbage r o o t f l y i n the f i e l d ( F i g . 5) (Coaker and W i l l i a m s , 1963) were used f o r comparing the b e e t l e p o p u l a t i o n s i n the experimental p l o t s . C a r a b i d s i n s i d e the p l o t s were sampled u n t i l h a r v e s t but those o u t s i d e were sampled u n t i l the end of September. 35. F i g u r e 5. The c a r a b i d s p e c i e s taken from p i t f a l l t r a p s i n the experimental f i e l d . From top l e f t : Bembidion lampros, Bembidion o b s c u r r e l l u m From bottom l e f t : P t e r o s t i c h u s m e lanarius, Harpalus a f f i n i s  36. F i g u r e 5. (cont.) From top l e f t : C a l a t hus f u s c i p e s , C l i v i n a f o s s o r Bottom: M a r a spp.  3.6 Egg counts The s t a r t o f egg co u n t i n g was determined by s e a r c h i n g f o r eggs i n the s o i l around young t r a n s p l a n t s i n the c o n t r o l p l o t s as o f t e n as p o s s i b l e i n l a t e A p r i l and e a r l y May. As soon as eggs were found (May 5) egg counting began i n a l l f i v e treatments. The same f o u r p l a n t s i n the middle row of each p l o t were used f o r egg counts throughout the c r o p p i n g season ( F i g . 6). The same p l a n t s were used f o r each and f o r subsequent counts and dead B r u s s e l s sprout ,plants were not r e p l a c e d . Eggs pres e n t around the p l a n t were sampled every 2 days. I t i s p r e f e r a b l e to choose an i n t e r v a l between samples t h a t i s s h o r t e r than the i n c u b a t i o n p e r i o d of the eggs s i n c e t h i s a v o i d s empty s h e l l s being counted. Eggs l a i d near the base of the stem and the f i r s t few mm of the top s o i l around each sampled p l a n t were removed f o r coun t i n g w i t h a moistened camel h a i r brush (Forbes, 1962). 38. F i g u r e 6. Counting of H. b r a s s i c a e eggs i n an experimental p l o t . 38 a. 3.7 I n s e c t i c i d e treatments B. t h u r i n g i e n s i s (Dipel) '(treatment 3) was a p p l i e d a t the recommended f i e l d r a t e of 1 lb/100 gal/acre(1.12 kg/1123 l i t r e / h a ) , f i v e times i n the season a t approximately t h r e e - week i n t e r v a l s (May 28, June 15, J u l y 3, J u l y 22, August 11). The m i c r o b i a l i n s e c t i c i d e was a p p l i e d as a f o l i a r spray mainly f o r c o n t r o l o f l e p i d o p t e r o u s l a r v a e . Methomyl (treatment 4) was a p p l i e d as a f o l i a r spray f i v e times (May 28, June 15, J u l y 3, J u l y 22, August 11) a t the recommended f i e l d r a t e of 1 lb/100 g a l / a c r e (1.12 kg/1123 l i t r e / h a ) f o r c o n t r o l o f aphids and l e p i d o p t e r o u s l a r v a e . C h l o r f e n v i n p h o s (treatment 5) was a p p l i e d once o n l y , on May 1 a t the recommended f i e l d r a t e of 1 oz/1000 f t (approx. 1 g/10 m) of row. The i n s e c t i c i d e was i n c o r p o r a t e d i n t o the s o i l approximately 1 cm deep i n a 10 cm diameter with the p l a n t a t the c e n t r e of the c i r c l e f o r e a r l y p r o t e c t i o n from damage by r o o t f l y l a r v a e . 3.8 C u l t u r a l p r a c t i c e s The p l o t s were weeded and i r r i g a t e d as the need arose. Some o f the B r u s s e l s sprout p l a n t s b o l t e d and went to seed, a process which normally takes two years to complete. S h o r t l y a f t e r the s e e d l i n g s were t r a n s p l a n t e d , a v e r y heavy f r o s t o c c u r r e d which probably t r i g g e r e d the p l a n t s i n t o f l o w e r i n g and seeding i n s t e a d of forming s p r o u t s . 40. 3.9 Harvest A t h a r v e s t (September 2-5), the t o t a l numbers of l i v i n g p l a n t s were reco r d e d e x c l u d i n g the f o u r p l a n t s i n each p l o t used f o r egg c o u n t i n g . Those which b o l t e d and went t o seed were a l s o recorded. The e f f i c a c y of B. lampros i n d e c r e a s i n g cabbage r o o t f l y damage was determined by the number of B r u s s e l s sprout p l a n t s t h a t were dead or w i l t e d , by the amount of l a r v a l damage on the r o o t s , by t o t a l f r e s h weight of the above ground p a r t s and by c o u n t i n g the cabbage r o o t f l y p u p a r i a i n 15 cm cores of s o i l , 12 cm deep and c e n t e r i n g on the main r o o t systems of 5 p l a n t s / p l o t . The p l a n t s were cu t o f f a t the root-stem j u n c t i o n f o r the f r e s h weights to be determined. The weights of the p l a n t s t h a t b o l t e d were determined separ- a t e l y from those t h a t formed s p r o u t s . A t h a r v e s t , 5 p l a n t s / p l o t were uprooted, the r o o t s washed and the maggot damage assessed v i s u a l l y as 0 ( c l e a n ) , 1 ( l i g h t ) , 2 (moderate), 4 (severe) or 8 (very severe) ( F i g . 7) (King and Forbes, 1954) . Methods of assessment of cabbage maggot damage based o n l y on the p r o p o r t i o n of p l a n t s k i l l e d o r stunted can be m i s l e a d i n g , because the numbers v a r y w i t h both weather con- d i t i o n s and the a v a i l a b i l i t y of s o i l moisture (Hughes, 1960). F i g u r e 7. Root maggot damage c a t e g o r i e s i n B r u s s e l s s p r o u t s . 1. C l e a n 2. L i g h t 3. Moderate 4. Severe 5. Very severe 41 a. 3.10 Puparia counts Overwintering p o p u l a t i o n s of cabbage r o o t f l y were estimated a t har v e s t by the numbers of l a r v a e and pupae found i n 5 s o i l samples per p l o t . Cores of s o i l 15 cm diameter by 12 cm deep were taken w i t h the topped p l a n t as the c e n t r e of the core u s i n g a core sampler. Larvae a re u s u a l l y r e s t r i c t e d t o the r o o t s of the p l a n t s and normally o n l y move a few cen t i m e t r e s away to pupate (de Wilde, 1947), but when p o p u l a t i o n s are hig h , some move as f a r as 10 cm (Coaker, 1966). The pup a r i a were e x t r a c t e d from the s o i l by f l o a t a t i o n on water. The pu p a r i a were washed from the s o i l - as i t passed through a coarse s i e v e (ten meshes per i n c h ) . The s i e v e d s o i l p l u s p l a n t remains were spread out on white paper and searched f o r l a r v a e and pupae. The numbers of f u l l and empty pupae i n each s o i l c o r e were recorded-'.. s e p a r a t e l y . The f u l l pupae were r e t a i n e d to d e t e r - mine p o s s i b l e p a r a s i t e development of Aleo c h a r a b i l i n e a t a , a s t a p h y l i n i d b e e t l e and the c y n i p i d , T r y b l i o g r a p h a rapae. 3.11 Laboratory t e s t s The m i c r o b i a l i n s e c t i c i d e , B. t h u r i n g i e n s i s , and the i n s e c t i c i d e s methomyl and c h l o r f e n v i n p h o s were used a t the c o n c e n t r a t i o n s n o r m a l l y recommended f o r c o n t r o l of l e p i d o p t e r - ous l a r v a e , aphids and cabbage maggot r e s p e c t i v e l y to d e t e r - mine the e f f e c t s of the three i n s e c t i c i d e s on B. lampros. S o i l from A b b o t s f o r d (sandy c l a y loam) was s i e v e d and oven d r i e d at 95°C to determine the moisture c o n t e n t which averaged 29.6%. Pots of 10 cm diameter were f i l l e d w i t h s o i l to 2.5 cm below the top and each pot was covered w i t h s i l k screen h e l d i n p l a c e by an e l a s t i c band. S i x to 10 mature D r o s o p h i l a melanogaster l a r v a e were added to each pot as food f o r B. lampros• The pots were p l a c e d i n p e t r i d i s h e s and watered from below. B. t h u r i n g i e n s i s ; D i p e l was sprayed on the s o i l t o the wet s u r f a c e . The r a t e used was e q u i v a l e n t t o the recommended f i e l d r a t e of 1 g / l i t r e of d i s t i l l e d water. F i v e B. lampros were added to each of 4 pots a f t e r d r o p l e t s of spray had been wiped d r y from the edges of the pot. The m o r t a l i t y was assessed 1, 2 and 4 days a f t e r treatment by c a r e f u l l y s e a r c h i n g the s o i l and examining B. lampros. In a second experiment, 5 times the o r i g i n a l dosage was used. Methomyl: Lannate a t the recommended f i e l d r a t e of 1 g/ l i t r e d i s t i l l e d water, was a p p l i e d as a spray to wet the s u r f a c e of the s o i l . D r o p l e t s of spray were wiped dry from the edges of the pot. F i v e B. lampros were added to each of 4 pots and pots were examined 1, 2 and 4 days a f t e r treatment. f o r B. lampros m o r t a l i t y . In a second experiment, the r a t e s f o r methomyl were 1/2, 1/4 and 1/8 of the o r i g i n a l dosage. In a t h i r d experiment the b e e t l e s were added 24 h a f t e r treatment u s i n g the r a t e s i n the second experiment. C h l o r f e n v i n p h o s : S i m i l a r pots were f i l l e d w i t h s o i l t r e a t e d w i t h c h l o r f e n v i n p h o s a t 10 ppm and 4 0 ppm oven d r y weight r e s p e c t i v e l y . The two treatments were r e p l i c a t e d f o u r times. M o r t a l i t y was assessed 1, 3, 5 and 7 days a f t e r 10 B. lampros were added t o t r e a t e d s o i l . 4. OBSERVATIONS AND RESULTS 4.1 Development o f cabbage r o o t f l y i n f e s t a t i o n The data show t h a t e g g - l a y i n g by the pest s t a r t e d on May 7 and i n c r e a s e d r a p i d l y to May 25 and reached a peak about May 28 ( F i g . 8). There were two peaks of egg l a y i n g , e n a b l i n g the season to be d i v i d e d i n t o two p e r i o d s : May 7 - June 27 and J u l y 11 - August 22. There were v a r i a t i o n s i n the number of eggs l a i d on p l a n t s w i t h i n the same p l o t and w i t h i n treatments. More eggs were l a i d i n the f i r s t gener- a t i o n when the p l a n t s were young than i n the second g e n e r a t i o n when the p l a n t s were mature. 4.2 Occurrence of Bembidion lampros The appearance of B. lampros c o i n c i d e d w i t h the main o v i - p o s i t i o n p e r i o d of the f i r s t g e n e r a t i o n of cabbage r o o t f l i e s . T h e r e a f t e r the numbers of eggs l a i d and of B. lampros taken both d e c l i n e d to i n s i g n i f i c a n t numbers. The p r o p o r t i o n of B. lampros caught i n the p i t f a l l t r a p s d e c l i n e d as the p l a n t s i n c r e a s e d i n s i z e . F i g . 9 r e p r e s e n t s the average number of B. lampros taken every two days from p i t f a l l t r a p s i n each p l o t f o r the v a r i o u s treatments. There was one major g e n e r a t i o n May 7 to June 18. Although B. lampros b e e t l e s were added to some of the treatments e a r l y i n the experiment, t h e r e was a n a t u r a l p o p u l a t i o n present i n the u n t r e a t e d c o n t r o l d e s p i t e t h e i r constant removal (Table I ) . 46. F i g u r e 8. O v i p o s i t i o n by the cabbage r o o t f l y , Hylemya b r a s s i c a e (Bouche): average number of eggs/ p l a n t on 52 dates f o r each treatment, May - August 1975. 46 a. NUMBER Or CGGypLANT/DA 47. F i g u r e 9. P o p u l a t i o n trends of B. lampros: average numbers taken every 2 days from p i t f a l l t r a p s i n each p l o t (4 t r a p s / p l o t ) f o r each treatment May - August 1975. NUMBER OF !!• LAMPROS 5/ PLOT j DATE / *v o o r r o / \ D 'I? n B o •-1 o 10 o •< K) O 'J tt. K <\> IT o 3 D D. jCO o rr < :r o D Q. ro n 3 a —i o TABLE I. Natural population of carabid beetles taken from p i t f a l l traps inside the b a r r i e r i n the four untreated p l o t s (64 sq m), May to August 1975 Species May June July August T o t a l Bembidion lampros 56 53 7 8 124 Harpalus a f f i n i s 10 1 2 6 19 Amara sp. 1 0 5 6 12 Bembidion sp. 5 0 0 0 5 Calathus fuscipes 0 0 2 1 3 Pterostichus melanarius 0 0 2 1 3 Monthly t o t a l s 72 54 18 22 166 49. 4.3 E f f e c t of Bembidion lampros on cabbage r o o t f l y eggs F i g . 10 r e p r e s e n t s the weekly mean of the number of cabbage r o o t f l y eggs l a i d and the corresponding B. lampros p o p u l a t i o n f o r the v a r i o u s treatments. The number of cabbage r o o t f l y eggs l a i d i n the c o n t r o l was more than double t h a t of any other treatment d u r i n g the f i r s t g e n e r a t i o n . As the number of eggs i n c r e a s e d , the a c t i v i t y o f the b e e t l e i n c r e a s e d and t h i s r e s u l t e d i n a g r e a t e r number being trapped. The maximum numbers o f b e e t l e s o c c u r r e d a few days a f t e r the maximum number o f eggs (Appendix Table 3 and 4 ) . Monthly a n a l y s e s o f the numbers o f r o o t f l y eggs i n the v a r i o u s treatments showed t h a t egg counts from the u n t r e a t e d p l o t s were s i g n i f i c a n t l y higher d u r i n g May and June than i n other treatments f o r the same p e r i o d (Table I I ) . Treatments which i n c l u d e d B. lampros were not s i g n i f i c a n t l y d i f f e r e n t i n May but the treatment which had c h l o r f e n v i n p h o s and B. lampros had s i g n i f i c a n t l y lower number of eggs than the other treatments i n June. There was no s i g n i f i c a n t d i f f e r e n c e among a l l t r e a t - ments i n J u l y and August. There were u s u a l l y fewer eggs i n p l o t s which had B. lampros than i n u n t r e a t e d p l o t s d u r i n g the f i r s t g e n e r a t i o n of the r o o t f l y . A n a l y s i s of f i r s t and second g e n e r a t i o n eggs o f cabbage r o o t f l y (Table I I I ) showed t h a t d u r i n g the f i r s t g e n e r a t i o n the mean numbers of eggs sampled from p l o t s w i t h and without B. lampros d i f f e r e d s i g n i f i c a n t l y a t the 5% l e v e l . T h i s was not so i n the second g e n e r a t i o n when B. lampros had disappeared. The unexpectedly h i g h number of eggs reco r d e d i n treatment 5 i n the second g e n e r a t i o n was due to a s i n g l e p l a n t w i t h c o n s i s t e n t l y higher egg counts. F i g u r e 10. O c c u r r e n c e o f Hylemya b r a s s i c a e ggs (•_ — — • — — — •) and c o r r e s p o n d i n g B e m b i d i o n l a m p r o s p o p u l a t i o n (•—• • •••) (weekly a v e r a g e ) i n t h e e x p e r i m e n t a l f i e l d . A r r o w s i n d i c a t e d a t e s when t h e i n s e c t i - c i d e s were a p p l i e d t o B r u s s e l s s p r o u t p l a n t s . 50 a to S M J NUMBER Op EGGS CO o CD o CO o O cn o oo o r o o o O CO o o Li o — c _ *< 65 H CD C is, — — — — — — — — — — — — a• _~. — — — — — — — — — — — — « O cn o C D O ro o o CO o I CD o CO o ro o O c Cu '51; TABLE I I . Monthly averages of cabbage root f l y eggs i n May,-June, July and August, 1975* Treatment May June J u l y August Treatment mean 1. Untreated 438a 492a 179 a 54 a 291 2. B. lampros only 196b 312b 264 a 69 a 210 3. Dipel and B. lampros 188b 335b 137 a 41a 175 4. Methomyl and B. lampros 254b 352b 135 a 37a 194 5. Chlorfenvinphos and B. lampros 167b 155c 376 a 76a 193 Monthly mean + S.D. 248 + 329 + 218 + 55 + 213 + 75.2 78.9 222.5 50.0 172.1 * Separation of means i n a month i s by Student - Newman - Keuls t e s t (S.N.K.), P = 0.05 (Zar, 1974). Values followed by the same l e t t e r are not s i g n i f i c a n t l y d i f f e r e n t (Error degrees of freedom, 12). There was no s i g n i f i c a n t (P - 0.05) treatment e f f e c t on other months according to the F-t e s t of a n a l y s i s of variance. TABLE I I I . The mean number of eggs sampled from plants i n the various treatments during the f i r s t and second generation of the cabbage root f l y i n 1975 Treatment 1st generation* May 7 - June 27 2nd generation J u l y 11 - August 22 1. Untreated 2. JB. lampros only 3. D i p e l and J3. lampros 4. Methomyl and J3. lampros 5. Chlorfenvinphos and B_. lampros 930.6a 509.5b 517.4b 606.6b 320.2c 204.1a 286.9a 146.4a 137.6a 406.6a Grand mean + S.D, 576.9 + 32.2 236.3 + 120.6 * Mean separation was by S.N.K., P = 0.05 (Zar, 1974). Values followed by the same l e t t e r are not s i g n i f i c a n t l y d i f f e r e n t (Error degrees of freedom, 12). 53. The percentage r e d u c t i o n i n the number of eggs due t o p r e d a t i o n by B. lampros d u r i n g the f i r s t g e n e r a t i o n of the r o o t f l y i s shown i n Tab l e IV. B. lampros i s shown to have reduced the numbers. The r e d u c t i o n was lowest i n methomyl treatments and h i g h e s t .in; c h l o r f e n v i n p h o s treatments. Methomyl was t o x i c t o the b e e t l e hence the low percentage egg r e d u c t i o n whereas D i p e l and c h l o r f e n v i n p h o s were not t o x i c t o the b e e t l e ; moreover c h l o r f e n v i n p h o s was t o x i c t o the cabbage r o o t f l y . As a r e s u l t t h e r e was a g r e a t e r percentage r e d u c t i o n i n egg numbers i n treatment w i t h c h l o r f e n v i n p h o s and B. lampros. TABLE IV. Percentage reduction i n egg numbers due to predation by B. lampros fo r the various treatments during the f i r s t generation of cabbage root f l y Treatment % reduction i n eggs* 1. Untreated 0 a 2. B_. lampros only 45 c 3. Dipel and 13. lampros 44 c 4. Methomyl and B. lampros 35 b 5. Chlorf envinphos and B_. lampros 66 d * Mean separation was by S.N.K., P = 0.05 (Zar, 1974). Values followed by the same l e t t e r s are not s i g n i f i c a n t l y d i f f e r e n t (Error degrees of freedom, 12). 55. 4.4 E f f e c t s o f i n s e c t i c i d e treatment on Bembidion lampros L a b o r a t o r y t e s t - The r e s u l t s showing the t o x i c i t y of i n s e c t i c i d e - t r e a t e d s o i l to B. lampros are giv e n i n Tab l e V. The three i n s e c t i c i d e s t e s t e d d i f f e r e d markedly both i n i n i t i a l and r e s i d u a l t o x i c i t y . Only methomyl caused hi g h m o r t a l i t y i n B. lampros. When f r e s h l y a p p l i e d t o the s o i l , i t was extremely t o x i c a t the recommended f i e l d r a t e of 1 g / l i t r e and a d u l t s exposed t o t r e a t e d s o i l s u f f e r e d 10 0% m o r t a l i t y i n the f i r s t day a f t e r treatment. D i p e l a t the same r a t e and c h l o r f e n v i n p h o s a t 10 ppm gave 0% m o r t a l i t y one day a f t e r treatment. The percentage m o r t a l i t y was 7 0% one day a f t e r treatment when the r a t e f o r methomyl was halved. Only when the recommended r a t e was reduced t o 1/8 was there no m o r t a l i t y of B. lampros. Increase i n the dosage r a t e of D i p e l f i v e f o l d and c h l o r f e n v i n p h o s f o u r f o l d d i d not i n c r e a s e the percentage m o r t a l i t y s i g n i f i c a n t l y . 56. TABLE V. Percentage mo r t a l i t y of B_. lampros exposed to i n s e c t i c i d e - treated s o i l , sampled p e r i o d i c a l l y a f t e r a p p l i c a t i o n I n s e c t i c i d e Rate ( g / l i t e r ) days a f t e r 1 % M o r t a l i t y s o i l treatment with 2 i n s e c t i c i d e s 3 D i p e l * 1 0 7 13 Methomyl 1 100 - - Untreated 0 7 13 Dipel 5 0 10 Methomyl 0.5 70 70 0.25 40 70 0.125 20 40 Untreated 20 40 1 3 5 7 Chlorfenvinphos 10 ppm 0 0 0 0 40 ppm 5 5 5 5 Untreated 0 0 0 0 * 1.12 kg/1123 l i t r e / h a i s rate recommended for b r a s s i c a crops; 1.12 kg Dipel contains 7. 26 x 10 9 IU. Dipel and methomyl were applied with a hand sprayer to wet the surface of the s o i l i n the pots. 57. F i e l d experiments - I i n v e s t i g a t e d the e f f e c t s of a p p l y i n g D i p e l , methomyl and c h l o r f e n v i n p h o s d u r i n g the a t t a c k p e r i o d s of cabbage maggot, aphids and l e p i d o p t e r o u s l a r v a e i n the presence of B. lampros. Monthly t o t a l s showed t h a t f o r June, treatment 5 r e t a i n e d the h i g h e s t numbers of B. lampros f o l l o w e d by treatments 3, 2 4 and 1 r e s p e c t i v e l y i n descending order (Table V I ) . A s i g n i f i c a n t r e d u c t i o n i n the numbers of B. lampros i n t r e a t - ment 4 d u r i n g the f i r s t g e n e r a t i o n of cabbage r o o t f l y r e s u l t e d i n an i n c r e a s e of cabbage r o o t f l y egg d e p o s i t i o n ( F i g . 10). But t h e r e was a r e d u c t i o n i n the numbers of eggs l a i d i n treatments 2, 3 and 5 where the predator p o p u l a t i o n had not been s u b s t a n t i a l l y reduced by i n s e c t i c i d e treatments. T h i s i s most ev i d e n t i n treatment 5 where the number of eggs was s i g n i f i c a n t l y lowest f o r the f i r s t g e n e r a t i o n of cabbage r o o t f l y (Table I I I ) . 58. TABLE VI. Monthly t o t a l s of B. lampros taken from p i t f a l l traps (4/plot) inside the b a r r i e r for the various treatments May - August 1975 Treatment May June J u l y August T o t a l 1. Untreated 56 53 7 8 124 2. B. lampros only 191 98 5 2 296 3. Di p e l an B. lampros 208 103 4 9 324 4. Methomyl and B. lampros 206 33 1 2 262 5. Chlorfenvinphos and B. lampros 213 100 3 3 319 Monthly t o t a l of B. lampros 894 387 20 24 1325 59. 4.5 C a r a b i d b e e t l e s other than Bembidion lampros The number of other c a r a b i d b e e t l e s taken from i n s i d e the b a r r i e r d u r i n g the experiment and t h e i r r e l a t i v e abundance i n d e c r e a s i n g order are presented i n T a b l e V I I . A t o t a l of 216 c a r a b i d s was removed from the experimental p l o t s . Outside the b a r r i e r , s i x major s p e c i e s of the f a m i l y Carabidae were taken, i n c l u d i n g B. lampros. L i k e those taken from i n s i d e the b a r r i e r , Harpalus a f f i n i s was the most abundant. Many more specimens of the same s p e c i e s were caught from o u t s i d e the b a r r i e r than from i n s i d e (Tables VII and V I I I ) . However, i n s i d e the b a r r i e r , B. lampros was the most numerous c a r a b i d trapped i n the u n t r e a t e d c o n t r o l f o l l o w e d i n descending order by H. a f f i n i s , Amara sp., Bembidion sp., Calathus f u s c i p e s and P t e r o s t i c h u s melanarius (Table I ) . There were no s i g n i - f i c a n t treatment e f f e c t s i n any month f o r any s p e c i e s caught i n s i d e the b a r r i e r (Appendix T a b l e 6). Covariance a n a l y s i s suggested t h a t the f i v e s p e c i e s d i d not appear t o have i n - f l u e n c e d the egg counts i n any meaningful way s i n c e the b e e t l e s were c o n s t a n t l y being removed from the experimental p l o t s . 60 . TABLE VII. Numbers of carabid beetles other than Bembidion lampros taken from eighty p i t f a l l traps i n the various treatments from May - August 1975 Species Untreated B.lampros Dipel Methomyl Chlorfen- T o t a l only and and vinphos & B.lampros B.lampros B.lampros Harpalus a f f i n i s Amara sp. Galathus fuscipes Pterostichus melanarius Bembidion sp. 19 12 16 4 7 25 14 11 19 11 23 102 48 27 24 15 T o t a l carabids 42 39 57 42 36 216 61. TABLE VIII. Numbers of carabid beetles taken from 20 p i t f a l l traps outside the b a r r i e r May - September 1975 Species May June J u l y August September T o t a l Harpalus a f f i n i s 225 30 66 289 116 726 Amara sp. 64 13 21 93 152 343 Calathus fuscipes 42 13 21 72 95 233 Pterostichus melanarius 0 0 19 105 35 159 Bembidion lampros 85 8 4 22 3 122 Bembidion sp. 14 1 0 0 0 15 Tot a l 430 55 131 581 401 1598 62. 4.6 Y i e l d and s u r v i v a l of B r u s s e l s sprout p l a n t s The percentage s u r v i v a l and mean weight of f r e s h B r u s s e l s sprout p l a n t s a t h a r v e s t are presented i n Table IX. There were no s i g n i f i c a n t d i f f e r e n c e s i n the average f r e s h weights of the percentage s u r v i v a l of p l a n t s i n the v a r i o u s treatments. Separate a n a l y s i s of the weights of b o l t e d p l a n t s and of those t h a t produced sprouts d i d not show any s i g n i f i c a n t treatment e f f e c t s . There was v e r y l i t t l e l o s s of p l a n t stand a t h a r v e s t and the number of p l a n t s t h a t b o l t e d to seed v a r i e d between treatments and between p l o t s (Appendix T a b l e 8). The per- centage s u r v i v a l of p l a n t s was very h i g h i n a l l the treatments d e s p i t e the l a r g e numbers of cabbage r o o t f l y eggs l a i d , e s p e c i a l l y i n the u n t r e a t e d p l o t s . These had the lowest percentage s u r v i v a l and treatment 5 with c h l o r f e n v i n p h o s the h i g h e s t . Root maggot i n f e s t a t i o n was c o n s i d e r e d l i g h t s i n c e l e s s than 5% of the p l a n t s u n t r e a t e d were k i l l e d . 63. TABLE IX. Percentage s u r v i v a l and mean weight of fresh Brussels sprout plants at harvest* Treatment Average no. of plants / p l o t that survived % s u r v i v a l Mean weight of fresh Brussels sprout plants (kg/plot) 1. Untreated 24.8 95.2 20.8 2. B. lampros only 25.5 98.1 19.8 3. Dipel and B. lampros 25.5 98.1 19.8 4. Methomyl and B. lampros 25.5 98.1 19.8 5. Chlorfenvinphos and B. lampros 25.8 99.0 24.1 Grand mean + S.D. 25.4 + 0.8 97.7 + 3.4 20.6 + 5.2 * There were no s i g n i f i c a n t (P = 0.05) treatment e f f e c t s on the weight of plants and percentage s u r v i v a l at harvest according to the F-test of anal y s i s of variance; no S.N.K. t e s t (Zar, 1974) was c a r r i e d out (Error degrees of freedom, 12). 64. 4.7 Cabbage maggot damage Root examination f o r cabbage maggot damage showed t h a t on the average, r o o t damage was moderate. The average damage index (Table X) shows t h a t treatments which i n c l u d e d By lampros had lower damage i n d i c e s than u n t r e a t e d c o n t r o l s . Treatment 5 had zero damage index and was s i g n i f i c a n t l y d i f f e r e n t from the other treatments. Some of the r o o t s examined i n treatments 1, 2 3 and 4 were found w i t h s c a r s , a sign, t h a t they had recovered from e a r l y maggot damage. Damage i n d i c e s f o r treatments 1 and 4 were not s i g n i f i c a n t l y d i f f e r e n t . 4.8 E f f e c t s of treatments on cabbage r o o t f l y p u p a r i a The average number of p u p a r i a per p l a n t a t h a r v e s t i s g i v e n i n Table XI. The t o t a l number of p u p a r i a (empty and f u l l ) was h i g h e s t f o r treatment 1 and lowest f o r treatment 5. Treatments 2, 3 and 4 were i n t e r m e d i a t e . On the whole the number of o v e r w i n t e r i n g p u p a r i a averaged 3.2 per p l a n t . Emergence r e c o r d s of H. b r a s s i c a e p u p a r i a c o l l e c t e d a t h a r v e s t r e v e a l e d 17% pupal p a r a s i t i s m by A l e o c h a r a b i l i n e a t a , a s t a p h y l i n i d b e e t l e . 65. TABLE X. Average index per plant for maggot damage a f t e r various treatments (20 plants, 5/plot) Treatment Number of roots i n each T o t a l damage Average damage damage category* index** index per plant*** clean l i g h t moderate severe very severe 0 1 2 4 8 1 0 7 2 2 10 3 0 9 4 0 7 5 20 0 7 5 1 7 1 0 9 2 0 9 4 0 0 0 0 49 2.5a 28 1.4c 35 1.8bc 41 2.lab 0 O.Od Grand mean + S.D. 1.5 + 0.7 * Damage category: 0, clean; 1, l i g h t ; 2, moderate; 4, severe; 8, very severe. ** Sum of the roots per category m u l t i p l i e d by the damage category. *** Mean separation of damage index i s by S.N.K. (Zar, 1974). Values sharing same l e t t e r s are not s i g n i f i c a n t l y d i f f e r e n t at 5% l e v e l (Error degrees of freedom, 12). TABLE XI. Average number of cabbage root f l y puparia per plant (20 plants, 5/plot) at harvest* Treatment Empty puparia** F u l l puparia Average** 1. Untreated 16.3a 3.2 a 9.7a 2. B. lampro s only 9.3b 4.8 a 7.1a 3. Dipel and B. lampros 11.4b 4.4 a 7.9a 4. Methomyl and B. lampros 12.4b 2.6 a 7.5a 5. Chlorfenvinphos and B. lampros 1.0c 1.0 a 1.0b Grand mean + S.D. 10.1 + 5.1 3.2 + 4.4 6.6+5/2 * S o i l core 15 cm diameter x 12 cm deep with p l a n t as center of sample ** Separation of means i s by S.N.K., P = 0.05 (Zar, 1974). Means followed by the same l e t t e r are not s i g n i f i c a n t l y d i f f e r e n t (Error degrees of freedom, 12). 5. DISCUSSION 5.1 L e v e l of o v i p o s i t i o n and consequent i n f e s t a t i o n The r e s u l t s of t h i s experiment showed t h a t i n f e s t a t i o n by the f i r s t g e n e r a t i o n of the cabbage r o o t f l y i s the c r i t i c a l f a c t o r i n the p r o d u c t i o n of e a r l y stem b r a s s i c a s . The peak of s p r i n g egg l a y i n g occurs when p l a n t s are s t i l l s m a l l . They may a l s o r e c e i v e c o n s i d e r a b l e numbers of second g e n e r a t i o n eggs, but t h i s i n f e s t a t i o n does not g r e a t l y a f f e c t p r o d u c t i o n s i n c e the p l a n t s are by t h i s time n e a r l y mature. T h i s supports the f i n d i n g s of King e t a l . (1957) who r e p o r t e d t h a t the c r i t i c a l p e r i o d of damage by r o o t maggots i s the 2 to 3 weeks between t r a n s p l a n t i n g and e s t a b l i s h m e n t . Coaker and F i n c h (1965) and Coaker (1969) have confirmed t h i s r e p e a t e d l y by showing t h a t s e r i o u s , r e d u c t i o n s i n y i e l d can u s u a l l y be prevented i f the crop i s w e l l p r o t e c t e d from cabbage maggot damage d u r i n g the f i r s t few weeks a f t e r p l a n t i n g . Egg d e p o s i t i o n i n the s p r i n g was h e a v i e r than i t was i n the summer ( F i g . 8 ) . T h i s has a l s o been noted by Gibson and Treherne (1916) and Forbes (1962) i n Canada, by M i l e s (1953) i n England, and by de Wilde (194 7) and Abu Yaman (1960) i n the Netherlands. M i l e s c o n s i d e r s t h a t t h i s i s not due to l a c k of a d u l t s but r a t h e r t o the f a c t t h a t the environment i n summer p r o v i d e s l i t t l e food to s u s t a i n the a d u l t s and as a r e s u l t they do not s u r v i v e to complete o v i p o s i t i o n . De Wilde i m p l i c a t e s p a r a s i t e s , p r e d a t o r s and weather c o n d i t i o n s and Forbes suggests t h a t as the season advances t h e r e i s a p r o g r e s s i v e l y g r e a t e r acreage of c o l e crops over which the 68. eggs are d i s t r i b u t e d so t h a t the number o f eggs t o be found on a sample of p l a n t s i s s m a l l e r . In t h i s study, t h e r e was a p r o g r e s s i v e decrease i n the number of eggs l a i d e s p e c i a l l y i n the second g e n e r a t i o n as the p l a n t s matured. Coaker (1967) and Hassan (1973) suggest t h a t mature p l a n t s may not a t t r a c t f l i e s f o r egg l a y i n g . 5.2 E f f e c t of weather on o v i p o s i t i o n by cabbage r o o t f l y In the experimental f i e l d , i n s p i t e of the l a r g e number of eggs l a i d , l a r v a l p o p u l a t i o n s were not h i g h . There was a g r e a t d i s p a r i t y between the numbers of eggs l a i d and the r e s u l t i n g i n f e s t a t i o n , p a r t i c u l a r l y i n the second g e n e r a t i o n . The response of the p l a n t s to a t t a c k depends on the p r e v a i l i n g weather; i n warm, wet c o n d i t i o n s a p l a n t can s u r v i v e an i n f e s t a t i o n of l a r v a e t h a t would k i l l i t i n a hot dry p e r i o d (Hughes, 1960). Weather a t the c r i t i c a l times of o v i p o s i t i o n , l a r v a l p e n e t r a t i o n and emergence may determine the numbers of cabbage r o o t f l i e s (Coaker and F i n c h , 1971; Matthewman and Harcourt, 197 2). Egg counts and o b s e r v a t i o n s i n the p r e s e n t study showed t h a t o v i p o s i t i o n was g r e a t e s t on calm, sunny days w i t h i n t e r m i t t e n t c l o u d cover. During dry p e r i o d s , eggs were found under l e a v e s which f e l l on the s o i l some cen t i m e t r e s away from the stem r a t h e r than immediately around the stem. Because of the prolonged dry p e r i o d d u r i n g the summer the p l o t s had to be i r r i g a t e d . T h i s probably s t i m u l a t e d o v i p o s i t i o n . B e i r n e (1971) r e p o r t e d t h a t hot weather i n c r e a s e s f e e d i n g of the a d u l t s but decreases egg l a y i n g . M o i s t u r e was found to have much i n f l u e n c e on i n f e s t a t i o n which tended to be h i g h i n wet p e r i o d s and low i n dry ones. The eggs are v e r y sus- c e p t i b l e to d e s i c c a t i o n , so t h a t up t o 90% may f a i l to hatch i n dry weather and the l a r v a e may d i e from d e s i c c a t i o n b e f o r e they can enter the r o o t s . A d u l t a c t i v i t y i s hindered by c o o l , wet weather and may be prevented by r a i n f a l l , w i t h consequent l i m i t a t i o n s on egg l a y i n g . M u k e r j i (1971) c l a i m s t h a t the newly hatched l a r v a i s the c r i t i c a l stage f o r s u r v i v a l and t h a t death by misadventure a t t h i s stage i s the k e y - f a c t o r respons- i b l e f o r p o p u l a t i o n change. Benson (1973) concluded t h a t the k e y - f a c t o r determining p o p u l a t i o n change was f a i l u r e of females to achieve p o t e n t i a l egg p r o d u c t i o n . 5.3 P o p u l a t i o n t r e n d of Bembidion lampros I n v e s t i g a t i o n of the e f f e c t i v e n e s s of B. lampros as a predator of cabbage r o o t f l y eggs showed t h a t the b e e t l e was p a r t i c u l a r l y a c t i v e d u r i n g the f i r s t g e n e r a t i o n of the r o o t f l y but was l e s s common i n the second g e n e r a t i o n ( F i g . 10). The sudden drop i n the p o p u l a t i o n o f B. lampros by mid-June c o u l d p o s s i b l y be accounted f o r by the f o l l o w i n g : A t t h i s time the a c t i v i t y of the b e e t l e had v i r t u a l l y ended. As a r e s u l t of fr e q u e n t capture and r e l e a s e , some of the b e e t l e s had been k i l l e d . The d e c l i n e i n the numbers might be r e l a t e d to the age or coverage of the cr o p . B. lampros caught i n cabbage p l o t s by M i t c h e l l ,(1963b) and Coaker (1965) a l s o d e c l i n e d as the p l a n t s i n c r e a s e d i n s i z e . The p o p u l a t i o n t r e n d of B. lampros ( F i g . 9) showed t h a t e a r l y emergence of the o v e r w i n t e r i n g p o p u l a t i o n began i n l a t e J u l y . These might be a new p o p u l a t i o n which emerged from pupae as suggested by M i t c h e l l (1963a). No attempt was made to study o v i p o s i t i o n p e r i o d s and f e c u n d i t y i n the l a b o r a t o r y 70. by breeding b e e t l e s i n c a p t i v i t y s i n c e the a d u l t s are c a n n i b a l i s t i c and i n cages they u s u a l l y eat most of t h e i r eggs soon a f t e r they are l a i d . Even i s o l a t e d g r a v i d females have been found to consume t h e i r own eggs ( M i t c h e l l , 1963a) . However, a d u l t p r e d a t i o n of eggs and l a r v a e appears u n l i k e l y under f i e l d c o n d i t i o n s , s i n c e the eggs are l a i d i n deep c r a c k s i n the s o i l ; the l a r v a e l i v e beneath and the a d u l t s l i v e on the s o i l s u r f a c e ( M i t c h e l l , 1963a). The frequency of the occurrence of ground b e e t l e s i n monoculture i s a l s o known to be g r e a t l y i n f l u e n c e d by weather and l e s s so by such c o n d i t i o n s as d e n s i t y of p l a n t growth and c o n f i g u r a t i o n of the ground (Jones, 1969; Skuhravy e t a l . , 1971). The f e e d i n g p e r i o d of B. lampros and some other c a r a b i d s i s known to be a f f e c t e d by temperature (Wishart et a l . , 1956; van D i n t h e r and Mensink, 1966). The annual f e e d i n g c y c l e of B. lampros showed t h a t the gut was empty d u r i n g the c o l d months ( M i t c h e l l , 1963a). Lab o r a t o r y e x p e r i - ments have shown t h a t the e f f i c i e n c y of p i t f a l l t r a p s v a r i e d d i r e c t l y with dryness of the s o i l ( M i t c h e l l , 1963b; Greenslade, 1964). In t h i s study, i t was observed t h a t more B. lampros were caught d u r i n g warm, dry and sunny p e r i o d s than when the weather was c o l d , wet and cloudy. The p o s i t i o n of the p i t f a l l t r a p s e s p e c i a l l y l a t e r i n the season when the p l a n t s gave g r e a t e r coverage than e a r l i e r , must have i n f l u e n c e d the numbers of B. lampros taken. 5.4 P r e d a t i o n of the egg stage of the cabbage r o o t f l y by B. lampros Methods f o r a p p r a i s i n g the a c t u a l and p o t e n t i a l import- ance of n a t u r a l eneimies have been reviewed by DeBach and B a r t l e t t (1964), DeBach and Huffaker (1971) and K i r i t a n i and Dempster (1973) who suggested t h a t more than one method of study should be used. In t h i s i n v e s t i g a t i o n , a d d i t i o n and e x c l u s i o n methods were used i n which B. lampros was i n t r o d u c e d i n t o c e r t a i n p l o t s and excluded from o t h e r s by means of p o l y - thene b a r r i e r s . T h i s i s of g r e a t advantage e s p e c i a l l y f o r n o n - f l y i n g forms, such as B. lampros, which are slow to d i s p e r s e . The main disadvantage of t h i s technique i s t h a t the p h y s i c a l environment i s m o d i f i e d by the mechanical b a r r i e r . Other workers have used these methods to determine the e f f e c t - i veness of some c a r a b i d s as p r e d a t o r s df r o o f f l y (Wright e t a l . , 1960; Coaker, 1965; Ryan and Ryan, 1973). Hassan (1969) r e p o r t e d t h a t b a r r i e r s d e t e r r e d o v i p o s i t o n by the r o o t f l y . T h i s needs f u r t h e r i n v e s t i g a t i o n . The e f f e c t i v e n e s s of B. lampros as a predator of cabbage r o o t f l y eggs was demonstrated. Untreated p l o t s had a g r e a t e r number of eggs than any other treatment and thus Had the h i g h - e s t i n d i c e s of damage and p u p a r i a (Table I I I and X). Although B. lampros may prey on any of the immature stages of the cabbage r o o t f l y , the r e l a t i o n s h i p between t h e i r numbers and the s u r v i v a l of the r o o t f l y eggs was the most c o n s i s t e n t . The f a c t t h a t t h e r e were no s i g n i f i c a n t d i f f e r e n c e s among treatments which included B. lampros i n May (Table I I ) , suggests that B. lampros was able to reduce considerably the number of eggs l a i d . It was i n fact, a f t e r the B. lampros population had declined i n June (Fig. 10) that treatment 5 had s i g n i f i c a n t l y lower egg numbers than other treatments (Table I I ) . This was probably due to the fact that chlorfen- vinphos i n treatment 5 was s t i l l toxic to H. brassicae females and t h i s resulted i n fewer eggs being l a i d near the base of the plants. As the number of eggs increased and decreased during the f i r s t generation, the number of B. lampros responded i n a s i m i l a r way except where methomyl i n s e c t i c i d e reduced the population of the beetle. The r e s u l t s also show that during May and June the number of root f l y eggs were s i g n i f i c a n t l y lower i n plots with B. lampros than i n plots without, but there was no s i g n i f i c a n t treatment e f f e c t for July and August, when B. lampros population had nearly disappeared (Table I I ) . A natural enemy may be of great importance i n reducing crop damage by the mortality i t causes i n a given pest generation. The number of empty puparia for each treatment gives an estimate of the number of larvae that penetrated and established them- selves i n the roots of Brussels sprout plants. Fewer clean roots were recorded i n untreated than i n treated p l o t s . Previous workers (Wishart et a l . , 1956) Coaker and Williams, 1963: Coaker, 1965) have demonstrated the role of predatory and p a r a s i t i c beetles i n reducing populations of immature stages of root f l y . Laboratory studies with housefly eggs showed that B. lampros consumed fewer eggs as egg density 73. decreased. Feeding d i d not occur every day. The maximum d a i l y consumption was about 20 eggs (van Dinther and Mensink, 1966). In a f i e l d experiment, Hughes (1959) i n d i c a t e d t h a t an average of 42% of the eggs p l a c e d around p l a n t s were l o s t every day. In the p r e s e n t i n v e s t i g a t i o n the r e d u c t i o n i n eggs due to p r e d a t i o n by B. lampros was c a l c u l a t e d to be 45% d u r i n g the f i r s t g e n e r a t i o n of r o o t f l y (Table I V ) . I t i s e v i d e n t t h a t B. lampros cannot alone give maximum p r o t e c t i o n a g a i n s t cabbage maggot, but the damage caused by the p e s t can be reduced s i g n i f i c a n t l y by the presence of B. lampros, a t l e a s t d u r i n g the f i r s t g e n e r a t i o n . A f u r t h e r r e d u c t i o n of cabbage r o o t f l y eggs occurs i n the second g e n e r a t i o n when other c a r a b i d s p e c i e s appear (Coaker, 1965). 5.5 S u s c e p t i b i l i t y of B. lampros to i n s e c t i c i d e treatments The l a b o r a t o r y method used f o r t e s t i n g the e f f e c t o f i n s e c t i c i d e s on B. lampros i n t h i s i n v e s t i g a t i o n , has the advantage o f p r o v i d i n g s o i l as a substratum. S o i l i s the n a t u r a l h a b i t a t of the cabbage r o o t f l y and i t s p r e d a t o r s and p a r a s i t e s . The s t u d i e s showed t h a t methomyl was t o x i c to B. lampros a t the recommended f i e l d r a t e . Even when the dosage was halved there was more than 60% k i l l . B. lampros was remarkably t o l e r a n t to both D i p e l and c h l o r f e n v i n p h o s (Table V ) . Methomyl i s moderately p e r s i s t e n t i n s o i l ; about 50 to 75% remains 30 days a f t e r a p p l i c a t i o n ( H i l l , 1970; Harvey, 1971). Where hig h p o p u l a t i o n s of aphids and l e p i d o p t e r - ous l a r v a e occur e a r l y i n the season, treatment w i t h methomyl might be harmful to b e e t l e p r e d a t o r s . I t has been shown t h a t a decrease i n the number of c e r t a i n p r e d a t o r s of the cabbage maggot would cause a p r o p o r t i o n a t e i n c r e a s e i n the s u r v i v a l of the p e s t and i n the amount of damage to stem b r a s s i c a s (Coaker and W i l l i a m s , 1963; Coaker and F i n c h , 1964) . Inform- a t i o n on the c r i t i c a l t o x i c i t y of an i n s e c t i c i d e and the l e n g t h of time i n which i t remains harmful to n a t u r a l enemies, i s of s p e c i a l importance as guidance f o r i n t e g r a t e d c o n t r o l . S h o r t - l i v e d i n s e c t i c i d e s may be a p p l i e d t o c o n t r o l the pest a t times when the u s e f u l i n s e c t s are absent or i n a stage of development t h a t i s not exposed t o the p o i s o n . The a p p l i c a t i o n of methomyl (treatment 4) a t the peak of egg l a y i n g i n the f i r s t g e n e r a t i o n s i g n i f i c a n t l y reduced the number of B. lampros. Consequently there was an i n c r e a s e i n the number of eggs which s u r v i v e d . ( F i g . 10). T h i s i n c r e a s e was r e f l e c t e d i n the h i g h damage index and the number of empty pu p a r i a i n methomyl treatments (Tables X and X I ) . The lower percentage r e d u c t i o n i n egg numbers (Table IV) due to p r e d a t i o n i n methomyl-treated p l o t s , confirmed t h a t methomyl has an adverse e f f e c t on B. lampros. Both D i p e l and c h l o r f e n - vinphos can be a p p l i e d s a f e l y a t the recommended f i e l d r a t e s i n c e they had no e f f e c t on the b e e t l e . The high degree of s p e c i f i c i t y permits the combination of these two i n s e c t i c i d e s w i t h m a c r o b i a l agents i n t h a t they may be a p p l i e d f o r c o n t r o l of s p e c i f i c p e s t s so as not to i n t e r f e r e w i t h c o n t r o l of other p e s t s by m a c r o b i a l agents. S i m i l a r f i n d i n g s have been r e p o r t e d f o r D i p e l (Jacques, 1965) and f o r c h l o r f e n v i n p h o s (Mowat and Coaker, 1967; F a l c o n e t a l . , 1968; Hassan, 1 9 6 9 ) . Adverse e f f e c t s of i n s e c t i c i d e s on the n a t u r a l enemies of cabbage r o o t f l y may be even more important w i t h a long term crop, such as B r u s s e l s s p r o u t s , i n which a high l e v e l o f c o n t r o l of the f i r s t g e n e r a t i o n a t t a c k i s probably necessary i n order to l i m i t a t t a c k by subsequent g e n e r a t i o n s . The i n c r e a s e i n the number of eggs i n p l o t s t r e a t e d w i t h c h l o r f e n v i n p h o s d u r i n g the second g e n e r a t i o n ( F i g s . 8 and 10) can be accounted f o r by the f o l l o w i n g : At t h i s time B. lampros had disappeared and the e f f e c t o f c h l o r f e n v i n p h o s which was a p p l i e d on May 1 probably had d e c l i n e d . At the recommended f i e l d r a t e c h l o r f e n - vinphos would be e f f e c t i v e f o r 45 days (B.C.D.A. 1 9 7 6 ) . The r e s u l t s from t h i s study i m p l i e s t h a t , when necessary, i t w i l l be s a f e to apply supplementary midseason treatments i n r e l a t i o n to the time of appearance of the second g e n e r a t i o n o f r o o t f l y to which other p a r a s i t e s and pr e d a t o r s are t o l e r a n t . I t i s of i n t e r e s t to note t h a t the i n c r e a s e i n the number of eggs i n c h l o r f e n v i n p h o s - t r e a t e d p l o t s was due to a s i n g l e p l a n t . Hawkes (1974) suggested t h a t the odour of host p l a n t s i s probably a f a c t o r i n the a t t r a c t i o n o f females t o the crop. Smith (1973) r e p o r t e d t h a t c e r t a i n chemicals o c c u r r i n g i n vapours from c r u c i f e r o u s p l a n t s , such as a l l y l i s o t h i o c y a n a t e (ANCS), can i n f l u e n c e the behaviour of r o o t f l y . T h i s needs f u r t h e r i n v e s t i g a t i o n . 76. 5.6 I n t e g r a t e d c o n t r o l of i n s e c t p e s t s of stem b r a s s i c a s The type o f i n s e c t i c i d e and i t s mode of a p p l i c a t i o n i s of v i t a l importance i n the c o n t r o l of i n s e c t p e s t s of b r a s s i c a . Attempts t o c o n t r o l one pest w i t h an i n s e c t i c i d e without an understanding o f the other fauna may l e a d to a chai n of r e a c t i o n s . There are documents t o support the f a c t t h a t a p a r t from the problem o f resurgence, secondary p e s t s may a r i s e from i n d i s c r i m i n a t e use of i n s e c t i c i d e s d i r e c t e d a t key pest (N.A.S., 1969; Adkisson, 1971; Reynold, 1971). The . dangers o f unwise use of i n s e c t i c i d e s are i l l u s t r a t e d by Dunning e t al_. (197 5) , who found t h a t B. lampros and F e r o n i a melanarius 111 (= P. melanarius) e f f e c t i v e l y f e d upon aphid nymphs on sugar beets, but were reduced by p a r a t h i o n sprays a g a i n s t the aphids. Other workers have demonstrated t h a t c a r a b i d s prey on aphids (Skuhravy, 1959; Dempster, 1972). The c a r a b i d Harpalus r u f i p e s Schr. together w i t h other i n s e c t s and a r a c h n i d s , p a r t i c u l a r l y Phalangium o p o l i o Linnaeus, accounted f o r a t l e a s t h a l f o f the n a t u r a l m o r t a l i t y o f eggs and l a r v a e of P i e r i s rapae on B r u s s e l s sprouts (Dempster, 1967). The use o f an i n s e c t i c i d e such as methomyl f o r the c o n t r o l of aphids and l e p i d o p t e r o u s l a r v a e on b r a s s i c a p l o t s may w e l l have adverse e f f e c t s on the n a t u r a l enemies of such i n s e c t s . The advantage of some p r o t e c t i o n from aphids, however must be weighed a g a i n s t the disadvantage of almost e l i m i n a t i n g p r e d a t o r y b e e t l e s . Mowat (1965) r e p o r t e d t h a t s t a p h y l i n i d b e e t l e s are at l e a s t twice as s u s c e p t i b l e t o organophosphorus i n s e c t i c i d e s 77. as the most s u s c e p t i b l e c a r a b i d s p e c i e s which was B. lampros. Use of s e l e c t i v e m a t e r i a l s and spot a p p l i c a t i o n s of broad spectrum i n s e c t i c i d e should minimize any adverse e f f e c t s a g a i n s t n a t u r a l enemies. A p r a c t i c a l consequence of r e d u c i n g egg numbers i s an i n c r e a s e i n y i e l d and t h i s has amounted t o as much as 4 0% i n s t u d i e s i n B r i t a i n (Wright e t a l . , 1960). Although the egg numbers were reduced i n treatments c o n t a i n i n g B. lampros i n t h i s study, there was no s i g n i f i c a n t d i f f e r e n c e i n y i e l d among treatments f o r two probable reasons. F i r s t , the cr o p was w e l l advanced when the r o o t maggots a t t a c k e d . Second, very few l a r v a e were a b l e t o p e n e t r a t e and get e s t a b l i s h e d . The low damage i n d i c e s appear t o support t h i s statement. Most of the p l a n t s t h a t were a t t a c k e d q u i c k l y r e c o v e r e d , hence the per- centage s u r v i v a l o f the p l a n t s was hig h i n a l l the treatments. I t seems l i k e l y t h a t y i e l d i s reduced o n l y when the a t t a c k i s heavy and occurs at the e a r l y stage. 78. 6 . SUMMARY AND CONCLUSIONS The p r i n c i p a l f i n d i n g o f t h i s s t u d y i s t h a t t h e c a r a b i d b e e t l e , Bembidion lampros i s a s s o c i a t e d w i t h d i m i n i s h e d s u r v i v a l o f cabbage r o o t f l y eggs. The amount o f p r e d a t i o n on the eggs may depend on t h e p o p u l a t i o n d e n s i t y and t h e a c t i v i t y o f t h e b e e t l e . B. lampros a l o n e may n o t be a b l e t o g i v e complete p r o t e c t i o n t o the c r o p e s p e c i a l l y when t h e a t t a c k by cabbage maggots i s heavy. I n t h e absence o f a s u i t a b l e i n s e c t i c i d a l t r e a t m e n t f o r cabbage maggot c o n t r o l , a r e d u c t i o n o f t h e c a r a b i d p o p u l a t i o n s c o u l d t h e r e f o r e have u n d e s i r a b l e consequences t h r o u g h the s u r v i v a l o f t h e r o o t f l y and t h e s e c o u l d be c o n s i d e r a b l y i n c r e a s e d i f t h e p o p u l a t i o n s o f p r e d a t o r y and p a r a s i t i c s t a p h y l i n i d b e e t l e s were a l s o reduce Egg counts may s e r v e as a w a r n i n g system f o r d e t e r m i n g the a p p r o p r i a t e time f o r i n s e c t i c i d e t r e a t m e n t . I t w i l l a l s o p r o v i d e i n f o r m a t i o n on the i n t e n s i t y o f a t t a c k . The i n s e c t i c i d e s t e s t e d d i f f e r e d i n t h e i r t o x i c i t y t o B. lampros. B. lampros was t o l e r a n t t o b o t h D i p e l and c h l o r - f e n v i n p h o s . Methomyl was t o x i c and i t r e d u c e d the B. lampros p o p u l a t i o n . Such r e s u l t s as t h e s e p o i n t t o t h e need f o r b o t h f i e l d and l a b o r a t o r y t e s t s ; a l t h o u g h l a b o r a t o r y t e s t s may i n d i c a t e the i n n a t e r e l a t i v e t o x i c i t i e s o f p e s t i c i d e s , t h e y c a n n o t always p r e d i c t t h e i r impact i n f i e l d s i t u a t i o n s . W i t h a f u l l e r knowledge o f t h e t o x i c i t y o f i n s e c t i c i d e s t o p r e d a t o r s we can p l a n r e l i a b l e c o n t r o l measures much more e a s i l y . 79. I t i s c l e a r l y d e s i r a b l e to enhance r a t h e r than l e s s e n the e f f e c t of B. lampros and other c a r a b i d p r e d a t o r s . In order to p r o t e c t n a t u r a l enemies and i n c r e a s e t h e i r b e n e f i c i a l e f f e c t , more s e l e c t i v e chemical c o n t r o l of the i n s e c t p e s t s of b r a s s i c a i s needed. 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M i c r o b i a l c o n t r o l of some l e p i d o p t e r o u s p e s t s of c r u c i f e r s . J . Econ. Entomol. 49:320-329. Van den Bosch, R. and V.M. S t e r n . 1962. The i n t e g r a t i o n of chemical and b i o l o g i c a l c o n t r o l of arthropod p e s t s . Ann. Rev. Entomol. 7:367-386. Van D i n t h e r , J.B.M. and F.T. Mensink. 1966. Egg consumption by Bembidion ustalatum and Bembidion lampros (fam. Carabidae) i n l a b o r a t o r y prey d e n s i t y experiments w i t h house f l y eggs. Mendel Landeouwhowsch Z o e k i n c s s t a S t a a t Gent. 30:1542-1554. Van D i n t h e r , J.B.M. and F.T. Mensink. 1971. U s e i o f r a d i o - a c t i v e phosphorus i n s t u d y i n g egg p r e d a t i o n by c a r a b i d s i n c a u l i f l o w e r f i e l d s . Meded. Fac. Landbouwet R i j k s u n i v . Bent. 36:283-293. V a r i s , A.L. 19 58. On the importance of the sowing time of c r u c i f e r s i n p r e v e n t i n g the damage caused by cabbage maggots (Hylemya spp.) on the b a s i s of t e s t s made on b i g - l e a f e d t u r n i p . Maataloust Aikakausk. 30:264-270. Wheatley, G.A. 1971. Pest c o n t r o l i n v e g e t a b l e s : some f u r t h e r l i m i t a t i o n s i n i n s e c t i c i d e s f o r cabbage r o o t f l y and c a r r o t f l y c o n t r o l . Proc. 6th Br. I n s e c t i c . Fungic. Conf. 2:386-395. Wishart, G., E.H. Colhoun and A.E. Monteith. 1957. P a r a s i t e s o f Hylemya spp. ( D i p t e r a , Anthomyiidae) t h a t a t t a c k c r u c i f e r o u s crops i n Europe. Can. Entomol. 89:610-639. Wishart, G., J.F. Doane and G.E. Maybee. 1956. Notes on b e e t l e s as p r e d a t o r s of Hylemya b r a s s i c a e (Bouch6). Can. Entomol. 88:634-639. Wright, D.W. 1954. Cabagge r o o t f l y on summer c a u l i f l o w e r . Grower 41:293-296. . 1956. Entomology r e p o r t . Rep. natn. Veg. Res. Stn. f o r 1955. p. 47. . 1971. Report o f the D i r e c t o r . Rep. natn. Veg. Res. Stn. f o r 1970. pp. 12-13. Wright, D.W., W.R. Howells and D.D. Bowe. 1956. N a t u r a l enemies of the cabbage r o o t f l y . Rep. natn. Veg. Res. Stn. f o r 1955. p. 47. Wright, D.W.,R.D. Hughes and J . W o r r a l l . 1960. The e f f e c t o f c e r t a i n p r e d a t o r s on the number of cabbage r o o t f l y ( E r i o i s c h i a b r a s s i c a e (Bouch6)) and the subsequent damage caused by the pest. Ann. a p p l . B i o l . 48:756-763. 98 . Z a b i r o v , Sh. M. 1961. C o n d i t i o n s i n f l u e n c i n g the s easonal c y c l e s of development of the beet f l y Pegomyia hyosciami (Panz.) and the cabbage f l y Hylemyia b r a s s i c a e (Bouche) ( D i p t e r a : Anthomyiidae). Rev. Ent. U.R.S.S. 40:275-281. Z a r f J.H. 1974. M u l t i p l e Range T e s t i n g . B i o s t a t i s t i c a l A n a l y s i s . P r e n t i c e - H a l l Inc. N.J. pp. 151-162. Appendix Table 1. Average number of eggs/plant/date f o r each treatment at 2 days i n t e r v a l May - August 1975 Date Untreated B. lampros Dipel Methomyl Chlorfenvinphos and and and B. lampros B. lampros B_. lampros 1 2 3 4 5 May 9 2.4 3.2 12 5.2 1.6 14 2.6 5.1 16 1.6 4.6 19 6.8 2.2 21 0.6 0.4 23 7.4 6.4 26 35.8 14.1 28 28.3 5.3 30 18.0 6.1 June 2 34.5 11.4 4 20.5 12.1 6 4.8 2.9 9 3.9 6.9 11 9.1 6.9 13 7.9 11.9 16 5.4 4.5 18 16.2 12.3 4.3 4.4 4.3 2.8 2.3 1.8 7.6 4.1 6.3 5.0 2.6 4.0 1.6 3.5 2.9 1.0 0.9 0.1 2.3 11.2 8.4 10.1 17.8 6.4 5.7 10.5 4.9 5.9 6.8 3.8 14.6 17.8 13.9 7.8 11.3 3.2 3.4 4.1 2.2 1.4 2.4 4.0 8.7 7.3 0.6 11.3 10.3 4.0 5.5 6.0 1.3 11.7 12.6 2.2 100 . Appendix Table 1 (cont.) Date Treatment 3 June 20 23 25 27 30 10.2 6.1 5.1 1.7 3.9 6.9 4.3 3.6 3.3 2.4 8.5 5.5 5.4 2.8 2.8 7.8 4.4 3.9 2.2 3.8 1.4 2.0 3.2 4.4 2.9 J u l y 2 4 7 9 11 14 16 18 21 23 25 28 30 2.1 2.5 4.3 1.1 2.0 5.7 8.6 4.8 4.0 4.1 1.8 2:;1 2.3 1.1 1.4 4.4 3.3 6.5 7.6 15.3 5.4 9.9 1.1 2.7 2.2 3.5 2.5 3.3 2.4 1.3 3.3 3.0 6.0 2.7 1.3 °2.8 1.6 2.3 0.9 2.8 0.6 0.6 0.8 2.6 5.1 7.8 2.6 3.5 1.8 2.4 0.9 1.4 4.9 4.9 5.6 4.1 8.3 7.2 12.0 12.8 18.8 7.4 2.6 2.7 2.6 101. Appendix Table 1 (cont.) Date Treatment 1 2 3 August 1 0.9 2.8 4 0.9 1.9 6 2.2 1.4 8 2.7 2.4 11 0.4 0.0 13 0.1 0.4 15 0.3 0.0 18 0.2 0.0 20 0.0 0.0 22 0.1 0.0 25 0.0 0.0 27 0.1 1.1 29 0.0 0.0 2.0 0.9 3.4 0.7 0.6 5.3 0.4 0.8 0.8 1.4 0.8 0.4 0.0 0.3 0.2 017 1.0 1.2 0.0 0.1 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 102 . Appendix Table 2. Average number of B. lampros taken from p i t f a l l traps (4/plot) each date at 2 days i n t e r v a l f o r the various treatments Date Untreated B_. lampros Dipel Methomyl Chlorf envinphos and and and B_. lampros B_. lampros B_. lampros 1 2 3 4 5 May 7 0.5 0.3 4.8 3.0 2.0 9 0.5 3.5 1.8 4.3 3.5 12 1.3 4.8 4.5 7.3 3.8 14 1.3 7.3 8.3 10.5 9.5 16 0.8 4.3 3.5 6.5 5.0 19 0.3 3.8 3.5 4.0 4.8 21 0.8 1.5 1.8 2.3 2.8 23 1.8 5.8 5.5 3.8 4.0 26 1.3 3.3 2.8 6.3 2.8 28 4.5 7.3 8.5 7.0 8.5 30 2.5 5.5 5.5 3.8 5.0 June 2 3.5 5.3 4.8 1.5 5.8 4 1.0 5.5 7.0 0.5 4.8 6 1.5 1.0 0i5 1.3 2.5 9 1.5 1.0 0.5 1.3 2.5 11 0.0 1.3 0.0 0.0 0.5 13 0.5 0.5 0.0 0.3 1.3 16 0.8 1.3 0.5 0.0 0.8 103 . Appendix Table 2 (cont.) Date Treatment 1 2 3 June 18 0.8 1.0 20 0.5 0.0 23 0.5 0.3 25 0.3 0.0 27 0.0 0.3 30 0.0 0.3 J u l y 2 0.0 0.0 4 0.0 0.0 7 0.0 0.0 11 0.0 0.0 14 0.0 0.0 16 0.3 0.0 18 0.0 0.0 21 0.5 0.0 23 0.3 0.0 25 0.3 1.0 28 0.0 0.3 30 0.5 0.0 1.5 0.0 0.8 0.0 0.3 0.0 0.3 0.0 0.3 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 1.0 0.0 0.8 0.5 0.0 0.3 0.0 0.3 0.0 104 . Appendix Table 2 (cont.) Date Treatment 1 2 3 August 1 0.0 0.0 4 0.0 0.0 6 0.5 0.0 8 0.5 0.0 11 0.5 0.0 13 0.0 0.0 15 0.0 0.0 18 0.0 0.0 20 0.0 0.0 22 0.0 0.0 25 0.0 0.0 27 0.0 0.0 29 0.0 0.0 0.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 0.0 0.0 0.3 0.0 0.0 0.3 0.5 0.3 0.0 0.0 0.0 0.3 0.5 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Appendix Table 3. Weekly counts of cabbage root f l y eggs on Brussels sprout plants (4 samples/plot) during the growing season May - August 1975 May June J u l y August T o t a l Treatment 9 16 23 30 6 13 20 27 4 11 18 25 1 8 15 22 29 38 150 236 1314 880 284. 473 332 122 127 260 206 100 64 51 8 1 4646 51 180 145 408 375 177 459 237 107 155 533 262 134 97 46 0 2 3368 69 247 77 358 357 215 455 310 128 115 197 108 77 50 36 0 0 2799 4 70 134 250 561 466 221 461 258 134 32 247 126 75 36 34 0 1 3106 5 69 193 182 222 274 109 117 114 194 235 450 635 126 152 28 1 1 3102 Weekly t o t a l 297 904 890 2863 2352 1006 1965 1251 685 664 1687 1337 512 399 195 9 5 17021 Appendix Table 4. Number of B_. lampros taken from p i t f a l l traps (4/plot) i n 20 plots i n s i d e the b a r r i e r each week for the various treatments May - August 1975 May June J u l y August Treatment Treatment 9 16 23 30 6 13 20 27 4 11 18 25 1 8 15 22 29 t o t a l 1 2 33 13 7 33 34 8 8 3 0 18 65 44 64 76 11 2 0 6 2 4 0 4 1 0 0 124 0 295 33 65 43 67 91 8 2 0 4 4 2 324 35 103 40 68 25 1 0 0 1 0 0 285 29 73 46 65 76 17 1 0 0 1 0 316 Weekly t o t a l 118 319 180 297 302 44 32 9 1 1 1 14 9 6 7 4 0 1344 107 . Appendix Table 5. Weekly mean of cabbage root f l y eggs and the corresponding mean of Bembidion lampros f o r the various treatments combined* Date Nos. of eggs Nos. of B. lampros May 9 15.5 hg 5 a 16 45.2 efg 16.9 b 23 44.5 efg 9.2 a 30 143.2 a 15.4 b June 6 117.6 ab 15.1 b 13 50.3 efg 2.2 c 20 98.9 be 1.6 c 27 62.6 def 0.5 c July 4 33.8 efgh 0.2 c 11 33.2 efgh 0.1 c 18 84.5 cd 0.1 c 25 66.9 de 0.7 c August 1 25.6 fgh 0.5 c 8 20 gh 0.3 c 15 9.8 gh 0.4 c 22 0.4 h 0.2 c 29 0.3 h 0.0 c Grand mean + S.D 50.1 + 184.1 3.9 + 0.7 * .Values sharing the same l e t t e r s are not s i g n i f i c a n t l y d i f f e r e n t a t the 5% l e v e l . 108 . Appendix Table 6. Number of other carabids taken inside the b a r r i e r from 80 p i t f a l l traps from May - August 1975 Species Treatment May June J u l y August Amara spp. 1 1 0 5 6 2 1 0 1 2 3 3 1 2 8 4 4 0 3 4 5 1 0 0 6 Mean + S.D. 2 + 2.4 0.2 + 0.9 2.2 + 3.6 5.2 + 6. H. a f f i n i s 1 10 1 2 6 2 3 0 5 8 3 6 0 6 13 4 7 1 7 7 5 7 0 5 11 Mean + S.D. 6. 6 + 7.9 0.4 + 1.2 4.4 + 4.5 9 + 9.6 C. fuscipes 1 0 0 2 1 2 2 0 3 2 3 2 0 3 6 4 1 0 0 5 5 0 0 0 0 Mean + S.D. 1.2 + 1.9 0 + 0 1.6 + 2.7 2.8 + 3.7 109 . Appendix Table 6. (cont.) Species Treatment May June J u l y August P. melanarius Bembidion spp. 1 2 3 4 5 Mean'+ S.D 1 2 3 4 5 0 0 0 0 0 0 + 0 5 6 0 2 1 Mean +S.D. 2.8+4.5 0 0 0 0 0 0 + 0 0 0 1 0 0 0.25 + 0.8 2 1 1 2 3 1.8 + 2.4 0 0 0 0 0 0 + 0 1 5 5 2 2 3 + 3.4 0 0 0 0 0 0 + 0 * There were no s i g n i f i c a n t treatment dif f e r e n c e s i n any month for any species, P = 0.05 according to the F-test of the ana l y s i s of variance, and no S.N.K. te s t was c a r r i e d out (Error degrees of freedom, 12). Appendix Table 7. Weekly t o t a l s of carabid species caught outside the b a r r i e r from 20 p i t f a l l traps May - September, 1975 May June July August September Species 9 16 23 30 6 13 20 27 4 11 18 25 1 8 15 22 29 5 12 19 26 Tota! Amara spp. 21 28 7 8 2 3 5 3 5 4 5 7 5 26 36 15 11 38 35 43 36 343 B. lampros 24 13 15 33 5 1 1 1 1 1 1 1 2 0 0 0 0 2 1 0 0 102 B. spp. 6 3 5 0 1 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 17 C. fuscipes 17 12 4 9 1 1 1 0 0 2 7 12 12 18 17 13 12 53 15 21 6 233 H. a f f i n i s 77 73 30 45 12 3 8 7 7 9 12 38 34 66 112 59 18 55 22 17 22 726 P. melanarius 0 0 0 0 0 0 0 0 0 2 7 10 9 14 41 25 16 14 5 5 11 159 Appendix Table 8. The numbers and weights (kg) of Brussels sprout plants at harvest Treatment No. of bolted plants No. of plants that formed sprouts T o t a l no. of pla n t s / p l o t Wt. of bolted plants Wt. of plants that formed sprouts T o t a l wt. of pl a n t s / p l o t 1 A 2 21 23 0.91 18.57 19.48 B 4 20 24 2.49 14.50 16.99 C 2 24 26 1.59 28.31 29.90 D 3 23 26 2.72 14.27 16.99 2 A 2 23 25 3.62 20.39 24.01 B - 26 26 0 17.67 17.67 C 2 24 26 1.13 16.99 18.12 D - 25 25 0 14.27 14.27 3 A 3 23 26 2.95 20.16 23.11 B 6 20 26 4.98 14.5 19.48 C — 25 25 0 16.31 16.31 D 3 22 25 1.81 18.35 20.16 4 A 4 21 25 2.04 14.95 16.99 B 3 23 26 2.04 16.54 18.58 C - 26 26 0 14.95 14.95 D 6 19 25 5.66 23.10 28.76 5 A 3 23 26 2.04 18.12 20.16 B 7 19 26 8.38 19.48 27.86 C 3 22 25 3.62 21.52 23.14 D 3 23 26 0.91 22.20 23.11 Appendix Table 9. Root examination and number of cabbage root f l y puparia per plant Treatment Sample no. A Damage B index C D A empty B C D Pupae A B f u l l C D 1 1 2 1 2 2 12 24 17 11 0 1 0 5 2 1 2 4 4 20 18 25 17 2 6 17 3 3 2 1 4 1 18 9 26 7 4 4 3 2 4 4 1 2 4 16 19 24 14 3 3 1 2 5 1 8 1 2 17 10 13 9 2 0 3 2 2 1 2 1 1 1 11 7 5 3 3 16 1 11 2 1 2 2 2 8 9 16 10 0 6 1 5 3 0 0 2 4 5 8 8 11 1 0 3 17 4 1 2 2 1 15 6 7 15 5 4 13 1 5 1 1 1 1 8 10 6 18 6 1 2 0 3 1 1 1 4 1 9 8 15 11 1 0 4 3 2 1 2 1 2 5 9 11 13 1 6 2 0 3 2 2 2 2 7 21 27 12 2 3 26 6 4 2 1 4 1 24 10 6 6 3 1 17 0 5 1 1 2 2 8 9 4 12 0 0 1 11 4 1 1 2 4 2 14 17 22 10 14 18 25 15 2 2 2 1 1 14 7 6 5 18 8 8 5 3 4 2 2 4 13 8 8 42 19 8 19 43 4 2 4 2 1 15 13 10 11 18 17 10 11 5 1 2 1 1 8 8 9 8 10 14 9 10 5 1 0 0 0 0 2 3 0 0 4 0 0 0 2 0 0 0 0 0 0 4 0 3 0 0 0 3 0 . 0 0 0 1 2 1 1 1 1 2 2 4 0 0 0 0 1 1 2 0 2 1 0 0 5 0 0 0 0 0 0 1 0 0 0 3 0 * A,B,C,D = plant r e p l i c a t e s 113 . Appendix Table 10. Percentage m o r t a l i t y of B. lampros 1, 2 and 4 days a f t e r exposure to fr e s h i n s e c t i c i d e - t r e a t e d s o i l I n s e c t i c i d e Replicates Days a f t e r 1 % M o r t a l i t y s o i l treatment with 2 i n s e c t i c i d e s 3 1st Experiment Dipel A 0 0 0 i g / B 0 20 20 (recommended rate) C 0 0 20 Methomyl A 100 - - • i g / B 100 - - (recommended rate) C 100 - - Untreated A 0 0 20 B 0 0 0 C 0 20 20 2nd Experiment Di p e l A 0 20 x 5 above B 0 0 Methomyl A 100 - . 1/2 above B 40 40 1/4 above A 40 40 B 40 40 1/8 above A 0 40 B 0 0 Untreated A 40 60 B 0 20 114 . Appendix Table 10 (cont.) I n s e c t i c i d e Replicates % Mortality- Days a f t e r s o i l treatment with i n s e c t i c i d e s 1 3 5 7 Chlorfenvinphos A 0 0 0 0 10 ppm B 0 0 0 0 (recommended rate) C 0 0 0 0 D 0 0 0 0 40 ppm A 0 0 0 10 B 10 10 10 10 C 10 10 10 0 D 0 0 0 0 Untreated A 0 0 0 0 B 0 0 0 0 C 0 0 0 0 D 0 0 0 0 Appendix Table 11. Names of p e s t i c i d e s and chemical d e f i n i t i o n of compounds used f o r preventing cabbage maggot damage i n Canada and other parts of the world Common name Trade name Chemical d e f i n i t i o n azinphos-methyl Guthion 0,0-dimethyl phosphorodithioate S_-ester with 3-(mercaptomethyl)-l,2,4-benzotriazin -4(3H)-one carbofuran* Furadan 2,3-dihydro-2, 2-dimethyl-7-benzofuranyl methyl carbamage chlorfenvinphos* Birlane 2-chloro 1-(2,4-dichlorophenyl)vinyl d i e t h y l diazinon * Basudin 0,0-diethyl 0-(2-isopropyl-6-methyl-4- pyrimidinyl) phosphorothioate fensulfothion* Dasanit 0,0-diethyl 0-p-(methyl s u l f i n y l ) p h e n y l phosphorothioate fonofos Dyfonate O-ethyl-S-phenyl-ethyl phosphonodithioate menazon Sayphos S-[(4,6-diamino-S-triazin-2-yl)methyl] 0,O-dimethyl-phosphorodithioate phorate Thimet 0,0-diethyl S-[?(ethylthio)methyl] phosphoro- d i t h i o a t e thionazin Zinophos 0,0-diethyl 0-2 p y r a z i n y l phosphorothioate t r i c h l o r o f o n Dylox Neguvon Dipterex dimethyl (2,2,2-trichloro-l-hydroxyethyl) phosphonate t r i c h l o r o n a t Agritox 0-ethyl £(2,4,5-trichlorophenyl)ethyl- pho sphoro th i o a t e * These i n s e c t i c i d e s are recommended for the co n t r o l of cabbage maggot i n B r i t i s h Columbia (B.C.D.A. 1976). 116. Appendix Table 12. Names of p e s t i c i d e s and chemical d e f i n i t i o n of compounds used for the co n t r o l of aphids and lepidopterous larvae on brassicas Common name Trade name Chemical d e f i n i t i o n Aphids demeton Sytox mixture of 0_, 0_-diethyl S_-(and 0) -2-[ (ethyl- t h i o ) e t h y l ] phosphorothioate diazinon Basudin 0,0-diethyl 0-(2-isopropyl-6-methyl-4- pyrimidinyl) phosphorothioate dimethoate Cygon 0,O-dimethyl-phosphorodithioate S-ester with 2-mercapto-N-methyl acetamide endosulfan Thiodan 1,4,5,6,7-hexachoro-5-norbornene-2,3- dimethanol c y c l i c s u l f i t e malathion Malathion d i e t h y l mercaptosuccinate S-ester with 0,0-dimethyl phosophorodithioate methamidophos Monitor 0,S-dimethyl phosphoroamidothioate mevinphos Phosdrin Dimethyl 2-methoxycarbonyl-l-methylvinyl phosphate methomyl Lannate S-methyl N[(methylcarbamoyl)oxy] thioace- tamidate naled Dibrom 1,2-dibromo-2, 2-dichloroethyl dimethyl phosphate Lepidopterous larvae chlorphenamidine Fundal N-(4-chloro-0-tolyl)-N, N-dimethyl form- amidine, hydrochloride chlorphenamidine Galecron N-(4-chloro-0-tolyl)-N, N-dimethyl form- amidine, hydrochloride diazinon Basudin 0,0-diethyl 0-(2-isopropyl-6-methyl-4- pyrimidinyl) phosphorothioate B a c i l l u s thur- D i p e l B a c i l l u s t h u r i n g i e n s i s (Berliner) i n g i e n s i s contains 25 x 10 9 v i a b l e spores/gram Appendix Table 12 (cont.) Common name Trade name Chemical d e f i n i t i o n endosulfan Thiodan leptophos Phosvel methomyl Lannate mevinphos Phosdrin naled Dibrom parathion Parathion 1,4,5,6,7-hexachloro-5-norbornene-2, 3- dimethanol c y c l i c s u l f i t e 0-(4-bromo-2, 5-dichlorophenyl) 0-methyl phenyl phosphorothioate S_-methyl N[ (methyl carbamoyl) oxy] t h i o - acetimidate Dimethyl 2-methoxy carbonyl-l-methylvinyl phosphate 1,2-dibromo-2,2-dichloroethyl dimethyl phosphate 0_,0_-diethyl 0_(p_-nitrophenyl) phosphoro- thioate

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