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The effect of various chemicals as selective herbicides for British Sovereign strawberries (Fragaria.. 1950

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THE EFFECT OF VARIOUS CHEMICALS AS SELECTIVE HERBICIDES FOR BRITISH SOVEREIGN STRAWBERRIES (Fragaria chiloensis). A thesis submitted i n parti a l fulfilment of the requirements for the Degree of MASTER OF SCIENCE IN AGRICULTURE i n the Department of HORTICULTURE THE UNIVERSITY OF BRITISH COLUMBIA by Jack Allen Freeman, B.S.A. Ap r i l , 1950 ABSTRACT Five experiments i n a l l were carried out with the object of studying the use of selective herbicides on B r i t i s h Sovereign strawberries. Before l a y i n g out a large r e p l i c a t e d experiment i t was f e l t the* (a) the general response of strawberry plants to various herbicides and (b) the eff e c t of these herbicides on both broad-leaved weeds and grasses should be determined. Small plots were l a i d out on a three year old strawberry plantation and subjected to 3 4 d i f f e r e n t treatments (Experiment I ) . Similar treatments were applied i n Experiments I I and I I I to newly seeded and established grasses. These treatments consisted of dif f e r e n t concentrations and mixtures of the following: 2 ,4-dichlorophenoxyaeetie aeid (2 ,4-D) Sodium s a l t of t r i c h l o r o a c e t i c a c i d (TCA) Ammonium salt of isopropyl N-phenyl carbamate (IPC) 2 methyl-4-chlorophenoxyacetic acid (MCP) Sodium pentaehlorophenate (POP) Ammonium s a l t of dinitro-O-secondary butyl phenol (DNOSBP) Potassium cyanate Emulsifiable pentachlorophenol The effects of these treatments on the strawberry plants, grasses and broad-leaved weeds are reported and discussed. 2. In the f i n a l experiment six treatments (£,4-D and 2,4-D plus IPC) were l a i d out in three replicates on a maiden British Sovereign strawberry plantation. Treatments of 1, 2, 3 and 4 pounds of 2,4-D per acre and 2 pounds of 2,4-D plus 40 pounds of IPC per acre were compared with a hand-weeded check. It was found from these experiments that (1) the sprays should be applied when the weeds are small and succulent, especially i s this true for annuals; and (2) that under conditions of this experiment a mixture of 2 pounds of 2,4-D plus 40 pounds of IPC can be safely recommended for the deweeding of British Sovereign straw- berry plantations provided i t i s not used when the plants are i n blossom. ACKNOWLEDGEMENTS The author acknowledges with thanks, the assistance given by Dr. G.H. Harris, Professor of the Department of Horticulture, University of British Columbia, and Dr. T.H. Anstey, Horticult- urist, Dominion Experimental Farm, Agassiz, B.C., in the planning and execution of the experimental work and manuscript. The writer also wishes to express his appreciation to Dr. A.F. Barss, Head of the Department of Horticulture, University of British Columbia, for his encouragement of the completion of this work; and to Mr. W.H. Hicks, Superintendent, Dominion Experimental Farm, Agassiz, B.C., for permission to carry on the f i e l d work at the Experimental Farm. TABLE OF CONTENTS Page INTRODUCTION 6 REVIEW OF LITERATURE , 7 EXPERIMENT I 14 Object 14 Materials and Methods 14 Results 13 Discussion 18 Conclusions 20 EXPERIMENT II 20 Object 20 Materials and Methods 20 Results 22 Discussion 25 Conclusions • • 27 EXPERIMENT III 27 Object , 27 Materials and Methods 27 Results • 28 Discussion ••• 29 Conclusions 30 EXPERIMENT 17 30 Objeot 30 Materials and Methods 30 Results 35 Page Effect on Grasses • 35 Effeot on Strawberry Plants • 49 Discussion • 50 Conclusions 56 EXPERIMENT 7 58 Object 58 Materials and Methods • 58 Results 61 Control of Various Weed Species » 61 Effect on Strawberry Plants 63 Condition of Strawberry Plants 65 Weed Control • 65 Discussion 70 Weed Control 70 The Effect on Strawberry Plants 74 Conclusions , • 76 SUMMARY 78 Effeot on Strawberry Plants • 79 Effect on Grasses 79 LITERATURE CITED 82 APPENDIX 86 FIGURES: Figure 1 - General View Showing the Layout of plots i n the Greenhouse 33 Figure 2 - Method of Spraying 34 Page Figure 3 - Mean Heights of Hog Millet 37 Figure 4 - The Effect of Pentaohlorophenol and Potassium Cyanate upon Br i t i s h Sovereign Strawberry Plants and Grass Seedlings 40 Figure 5 - The Effect of 2,4-D and 2,4-D plus IPC upon Various Grasses 41 Figure 6 - Weight of Creeping Red Fescue Clippings 44 Figure 7 - Weight of Perennial Rye Grass Clippings 45 Figure 8 - Weight of Orchard Grass Clippings . 46 Figure 9 - Weight of Hog Millet Clippings .... 47 Figure 10- General Layout of Experiment V and Method of Spraying • 66 Figure 11- Effects of 2,4-D on Strawberry Plants , 67 TABLES: Table 1 - Treatments Applied to Established British Sovereign Strawberry Plants (1949) 15 Table 2 - Treatments Applied to Well Establi- shed Grass and Weed Plots 21 Table 3 - Height of Hog Millet at 12 days Following the Treatments 36 Page Table 4 - Amount of Grass remaining one Month after Treatments were Applied (Weight of Clippings).... 43 Table 5 - Sensitivity of Some Monocotyledon- ous Plants to IPC 57 Table 6 - Soil Analysis of Strawberry Plots Obtained by Spurway Tests •• 60 Table 7 - Effect of the Various Treatments upon the Broad-leaved Weeds and Grasses • 64 Table 8 - The Condition of the Strawberry Plants 68 Table 9 - Effect of the Various Treatments upon the Weeds 69 6. THE EFFECT OF VARIOUS CHEMICALS AS SELECTIVE HERBICIDES FOR BRITISH SOVEREIGN STRAWBERRIES (Fragaria chiloensis). INTRODUCTION Information on the use of herbicides for weed control in strawberries i s limited, but grower interest has increased to the point where recommendations for safe usage are needed. From the limited investigations (6,13,17,19,23) of the past three years i t has been shown that strawberry varietal responses to 2,4-D (this abbreviation w i l l be used for 2,4-dichlorophenoxyacetic acid throughout the paper) are wide and, for that reason, i t i s imperative that the response of the British Sovereign strawberry to 2,4-D be determined since this variety i s used extensively i n commercial plantings i n the Fraser Valley. In addition a number of new herbicides have made their appearance since 2,4-D and i t i s possible that some of them may have a place for weed control i n strawberries. With the above points i n mind the following experiments were carried out: 1. An exploratory experiment with several herbicides and a large range of concentrations to determine their effect 7. on British Sovereign strawberry plants. 2. An exploratory experiment with several herbicides and a large range of concentrations to determine their effect on well established grass and weeds. 3. A follow up of experiments 1 and 2 conducted i n the greenhouse under controlled conditions to determine the effeot of various concentrations of the more promising herbicides on newly germinated grass seedlings. 4. An experiment i n the greenhouse with various combinations and concentrations of 2,4-D and Isopropyl N- phenylcarbamate (I.F.C.) to determine the most effective combinations to be used i n deweeding of strawberries. 5. An experiment to study the effeot of various concentrations of 2,4-D and 2,4-D supplemented with I.P.C, on both weeds and strawberry plants i n the f i e l d . REVIEW OF LITERATURE Strawberry weed control has long been a laborious and expensive process where mild winters, such as experienced in the Fraser Valley, promote the germination and growth of grasses and weeds throughout the winter months. Annual broad-leaved weeds and grasses are the most troublesome i n the first-year bed, while the fr u i t i n g bed often becomes infested with perennial weeds and grasses. Growers estimate 8. that costs of cultivation, hoeing, and hand weeding run up to $100 and more per acre per season.(18) Various methods and suggestions have appeared from time to time in the literature for easing this problem. However, as mentioned i n the introduction, information on the use of herbicides for weed oontrol i n strawberries i s limited. Bush (2) describes a method using t a r - o i l for controlling weeds i n strawberry beds. Tar-oil at &% i n water i s applied between the rows i n autumn, taking eare to avoid the strawberry crowns. When the weeds die the s o i l i s l i g h t l y turned, leaving a clean bed. Elder, Elwell and Romans (8) state that there i s some evidence that most strawberry varieties are f a i r l y resistant to 2,4-D. They state i t may be used throughout the growing season the f i r s t year plants are set, but on older beds i t should be used only after the harvest season. Some distortion of leaves and runners w i l l be seen, but the plants usually recover and continue normal growth. Applications three to four days after thorough shallow cultivations are most effective. The suggested rate i s one pound (aoid equivalent) per acre, with applications not closer than four weeks unless heavy rain should f a l l i n the meantime. The Division of Horticulture, Dominion Experimental Farm Service, (23) reports that a sodium salt, an amine salt and a butyl ester of 2,4-D each at the rates of one-half, one and two pounds aoid equivalent per acre were applied to 9 . the foliage of several varieties of strawberry plants. Included i n the test were the varieties: Ambrosia. Big Joe, Crimson Clow. Daybreak. Fairpeake, Gandy, Massey, Maytime, Premier, Red Star, Redwing and a seedling 0-374. The one- half pound rate caused slight curvature and twisting of the petioles of a l l the varieties. Moderate distortion of a l l the varieties resulted from the two pound rate. Application of the amine resulted in injury similar to that caused by the sodium salt.. The degree of distortion, however, was greater and ranged from slight to considerable. The ester was the most injurious and caused distortion ranging i n degree from slight to severe. Varietal differences i n susceptibility to the 8,4-D were evident. The variety Fairpeake appeared to be the most resistant to the 2,4-D. Reports (21) from four looations indicate that fruiting plants of three varieties are tolerant of 2,4-D applications up to one pound, acid equivalent, per acre. Higher dosages caused severe distortion of leaves but did not k i l l the plants nor reduce the production of runner plants. No differences between amine salt, sodium salt and ester formulations were reported. Seedling plants, however, showed a great variation in tolerance. Control of annual weeds was satisfactory, in a l l cases, but one pound did not control perennial weeds. Carder (3) reporting on the control of dandelions in strawberries by 2,4-D states that rates of 8,16, and 32 ounces, acid equivalent, per acre of butyl ester of 2,4-D 10. were applied at three growth stages of Dakota strawberry, viz., just previous to flowering, at time of flowering, and in late summer after harvest* The strawberry plants showed no injury from 8 and 16 ounce rates but exhibited curling of leaves from the 32 ounce spraying at time of flowering. Most complete k i l l of the dandelions was effected by treating before the strawberry plants were i n f u l l flower. Spraying at this time eliminated the dandelions 55, 70 and 80 per cent with the 8, 16 and 32 ounce rates respectively. Many old established dandelions had only their tops k i l l e d and later f u l l y recovered. Nylund (17) studying the use of 2,4-D for weed control i n Arrowhead strawberries found that the isopropyl ester at one pound per acre and the sodium salt at one and two pounds per acre, satisfactorily controlled broad-leaved weeds. Some distortion of the leaves and runners of the strawberry plants was noticeable. Leaf counts and runner plant counts indicated no detrimental effect of the 2,4-D on either leaf production or on runner plant formation. According to Carlson (4) spraying against broad- leaved weeds with 2,4-D at 1,000 parts per million was successful without damage to the strawberry plants at any time in the f i r s t season of planting — i n which no crop i s required — and after harvest i n the second year. Carlson and Moulton (5) investigating the use of the ammonium salt of trichloroacetate, the sodium salt of 11. triehloroacetate, ammonium thiocyanate and herbieide "PBM, in the eradication of grasses, and the effect of these chemicals on strawberry and raspberry plants found that both the ammonium and sodium salts of triehloroacetate (TCA) gave slow but effective control of couch grass, Agropyron repens. and Kentucky bluegrass, Poa pratensls. under greenhouse conditions, i f applied at the rates of 150 -£00 pounds per acre i n the case of well established grass and of 40 - 80 pounds per acre i n the case of young growth. After a gradual colour change the leaves became chlorotlc and withered 4 weeks after treatment. Ammonium thiocyanate proved less effective than the two salts of TCA, and WPB". The latter k i l l e d broad-leaved weeds without injuring the grasses. The strawberries were k i l l e d by the TCA salts when applied at herbicidal strength. A preliminary report by S l i f e and Ball (19) states that TCA was applied to the Premier variety of strawberry, at the rates of 10, 20, 30, 40, and 50 pounds, acid equivalent, per acre. In a l l plots, plants were severely burned and on a later date, there was no evidence of recovery. Otis (18) states that good results were obtained with a mixture of water and Diesel o i l f o r t i f i e d with Dow General Weed K i l l e r (a concentrate of Dinitro-o-secondary- butylphenol). Proportions used were 1 quart of Dow General, 30 gallons of Diesel o i l , and 100 gallons of water. The material was sprayed so as to thoroughly wet the vegetation. 12. On small weeds 125 to 150 gallons per acre are usually sufficient. The oil-dinitro-water mix k i l l s hack top growth but does not injure crowns or root systems of perennials. Hence strawberries treated even after growth was well started were only temporarily "burned" back. By the same token, of course, annual weeds and grasses are eradicated, but establish- ed perennial weeds are not. Much work, the principles of which may prove of value i n the weed control of strawberries, has been done, by Hitchcock and Zimmerman (12) on the activation of 2,4-D by various adjuvants. They found that mixtures of 2,4-D and certain adjuvants (Benolor 3C, ammonium thiocyanate, ammonium sulphamate, Hammond's Weed K i l l e r , d i a l l y l maleate, sodium bicarbonate, and sodium chloride) were more effective herbicides than any of the individual components used at the same conoentration. Adjuvants which funotioned as aotivators of 2,4-D included wetting agents, solubilizers, emulsifiers, penetrants, hormones other than 2,4-D and toxicants commonly used as contact herbicides. Mixtures containing lethal and sub-lethal concentrations of contact herbicides increased the activity of the hormone-like preparations with respeot to the induction of hormone-curvature responses, i n i t i a l injury to foliage, and k i l l i n g of the entire plant. The herbicidal activity of these mixtures increased with increasing concentrations of the contact weed k i l l e r up to the point where the mixture was no more effective than the 13. contact weed k i l l e r used alone at the same concentration as in the mixture. Relatively high concentrations of contact herbicides (1$ to 30%) were required to prevent 2,4-D from inducing additive effects. They conclude that i t i s believed that more effective general-purpose herbicides than those used to date are l i k e l y to contain more than one hormone, at least one toxicant, and additional adjuvants which are effective as wetting agents, solubilizers, penetrants, emulsifiers, and stickers. A description i s given by Hance (10) of a method used i n the Hawaiian Islands to supplement the herbicidal effect of 2,4-D and at the same time reduce i t s injurious effect on sugar-oane. It has been found that i n certain cases the amount of 2,4-D applied may be reduced to a concentration harmless to germinating sugar-oane — say two pounds per acre — while at the same time maintaining for three months or longer i t s f u l l pre-emergence herbicidal effect on the f i e l d , provided that 2,4-D i s supplemented with about five times i t s weight of H.S.P.A. activator (pentachlorophenol, or sodium pentachlorophenate). Some similar method might prove of value i n the weed control of strawberries. 14. EXPERIMENT I Object: To determine the effect of various concentrations of several different herbicides and combinations of herbi- cides on Bri t i s h Sovereign strawberry plants. Materials and Methods: Plots one square yard i n area of established British Sovereign strawberry plants were sprayed with the various treatments as shown i n table 1. A l l sprays were applied with a knapsack sprayer. General notes were taken periodically following the applications and the effect of the sprays upon the strawberry plants noted. 15. Table 1 - Treatments Applied to Established British Sovereign Strawberry Plants. (1949) Treat: No. Material Rates per acre Volumes gals/aore Date sprayed Temp 1*. TCA 25,40,80,100 & 200 pounds 150 May 23 v 72° 2. TCA plua 2,4-D 25,40,80,100 & 200 pounds 1000 ppm 150 May 23 72° 5. 2.4-D 1000 ppm 150 May 25 73° 4. IPC 5,10,20,30,40,50, 60,70 & 80 lb». 150 May 25 73° 5. IPC plus 2,4-D 5,10,20,30,40,50 60,70 & 80 lbs. 1000 ppm 150 May 25 73° 6. MCP 1 & 2 lbs. 150 June 7 71° 7. PCP 24 lbs. 150 June 8 75° 8. DNOSBP 2qt/100 gal H20 75 June 8 75<> 9. Untreated Legend: TCA - Sodium salt of Trichloroacetic acid 2,4-D - 2,4-Diohlorophenoxyacetic acid IPC - Ammonium salt of Isopropyl N-phenol carbamate MCP - 2 methyl-4-chlorophenoxyacetic acid PCP - Sodium pentachlorophenate DNOSBP- Ammonium salt of dinitro-0-secondary butyl phenol 16 RESULTS On May 24 (one day following spraying with TCA and TCA plus 2,4-B) TCA at 25 pounds per acre caused marginal browning of the strawberry leaves and this browning increased directly with increased concentration of TCA u n t i l at 100 and 200 pounds per acre the leaves were completely browned. Treatment 2 (TCA plus 2,4-D) gave similar results. On June 17 (twenty-five days following spraying with TCA and TCA plus 2,4-D) new leaves appeared from a l l plants treated with TCA and TCA plus 2,4-D. The plants sprayed with 2,4-D at 1000 ppm showed slight curvature and twisting of petioles and curling of leaves. Treatment 4 (IPC) regardless of concentration appeared to have no effect upon the straw- berry plants. Treatment 5 (IPC plus 2,4-D) affected the plants the same as described above for 2,4-D alone. Treatment 6 (MCP) caused slight curling of the leaves and twisting of petioles. Treatment 7 (PCP) caused slight browning to leaves and blossoms and also caused considerable damage to the f r u i t . Treatment 8 (DNOSBP) caused partial browning of the leaves. A f i n a l survey was made on August 1 of a l l plots and complete notes taken. Following are a few brief extracts taken from these notes: Treatment 1 (TCA) The majority of the plants i n TCA treated plots were dead. The odd plant in plots treated with 25, 40 and 80 17. pounds of TCA showed a few small green leaves breaking from the crown, but i n plots treated with 100 and 200 pounds per acre a l l plants were completely dead. Treatment 2 (TCA plus 2.4-D) The results from these treatments were the same as described above for TCA only the plants were i n a worse condition. Treatment 5 (2.4-D) The plants in these plots appeared to be developing normally a l l distortions of petioles and leaves had disappeared. Treatment 4 (IPC) A l l IPC treated plants appeared to be developing normally and were as vigorous as the untreated plants. Treatment 5 (IPC plus 2.4-D) Plants under this treatment also appeared to be developing normally though not quite as vigorously as those plants treated with IPC alone. Treatment 6 (MCP) Plants treated with MCP at 1 and 2 pounds per acre appeared to be recovering, but leaves were rather small. The plants as a whole appeared siok. Treatment 7 (POP) Plants were recovering, but the leaves appeared smaller than normal. Also no f r u i t was obtained from these plants after spraying since as mentioned previously this treatment dried up the blossoms and f r u i t . 18. Treatment 8 (DNOSBP) Plants treated with DNOSBP had recovered though i n general the plants were smaller than those treated with IPC. DISCUSSION The results with TCA in this experiment are i n agree ment with those obtained by Carlson and Moulton, (5) who report that strawberries were k i l l e d by the TCA salts when applied at herbicidal strength. The F i f t h Annual North Central Weed Control Conference Research Report (21) states that TCA, at a rate as.low as 10 pounds, acid equivalent, per acre caused severe injury to strawberry plants. Thus i n light of these reports and the results obtained i n this experiment i t appears that TCA i s worthless as a weedicide for strawberries. On the other hand, IPC apparently did not have any effect upon the strawberry plants. Lachman (14) found that IPC was valuable as a selective herbicide i n that i t effectively k i l l s grasses with l i t t l e or no harm to broad- leaved plants. Thus IPC should prove useful as a control for grasses in strawberry plantings. From the results of this experiment i t i s also seen that 2,4-D at 1000 ppm and IPC plus 2,4-D apparently did not have any lasting detrimental effects upon the strawberry plants. The F i f t h Annual North Central Weed Control 19. Conference Research Report (21) states that reports from four locations indicate that fruiting plants of three varieties of strawberries are tolerant to 2,4-D applications up to one pound, aoid equivalent, per acre. Higher dosages caused severe distortion of leaves but did not k i l l the plants nor reduce the production of runner plants. No differences between amine salt, sodium salt and ester formulations were reported. Carder (3) reported that strawberry plants showed no injury from 8 and 16 ounce rates of 2,4-D, but exhibited curling of leaves from 32 ounce spraying. According to Davidson (6) 16 ounce concentrations of 2,4-D caused slight formative effects on the new strawberry foliage (variety Premier), which emerged immediately affeer treatments. Nylund (17) states that leaf counts and runner plant counts indicated no detrimental effect of 2,4-D on either leaf production or on runner plant formation (variety Arrowhead). S l i f e and Ball (19) report that Premier strawberry was sprayed with 0.50, 0.75, 1.0, 2.0, and 3.0 pounds per acre of the amine preparation of 2,4-D. The twisting and durling effect was slight on the 0.50 and 0.75 pound application, but rather severe on the 1, 2 and 3 pound rates. Within one month from application, a l l plots appeared normal and showed no apparent effects of treatment. According to Klein (13) the premier strawberry tolerated a weed-killing spray of 1,400 ppm of 2,4-D in July and August; two applications were made, three weeks apart. It i s apparent from the results of this experiment and of those quoted that 2,4-D and 2,4-D plus IPC 20. hold promise as selective weedicides for British Sovereign strawberries. From the results of this experiment i t i s easily seen that PCP, MCP and DNOSBP are a l l too injurious to actively growing strawberry plants* It i s possible that these chemicals may prove useful as weedicides i f applied after harvest or when the plants are dormant* CONCLUSIONS Of the various chemicals tested in this exploratory experiment i t appears that 2,4-D and 2,4-D supplemented with IPC offer the greatest promise as selective herbicides for British Sovereign strawberries during the growing period. Furnher experimentation i s definitely warranted i n order that complete information as to most effective concentrations and combinations of these chemicals can be determined. EXPERIMENT II Object: To determine the effect of various concentrations of several different herbicides and combinations of herbicides on well established grass and weeds. Materials and Methods: Plots one yard square were l a i d out on a weed Table 2 - Treatments Applied to Well Established Grass and Weed Plots. (1949) 21. Treat; Material No. Rates per acre Volumes Date Temp: gals/acre sprayed P 1. TCA 25,40,80,100 & 200 lbs. 150 May 26 71° 2. TCA plus 2,4-D 40 & 100 lbs. 1000 ppm 150 May 26 71° 3. IPC 10,30,50 & 80 lbs. 150 May 26 71° 4. IPC plus 2,4-D 10,50 & 80 lbs. 1000 ppm 150 May 26 71° 5. MCP 1 & 2 lbs. 150 June 7 71° 6. PCP 24 lbs. 150 June 8 75° 7. DNOSBP 2 qt/100 gal H„0 75 June 8 75° 8. Untreated Legend: TCA - Sodium salt of Trichloroacetic acid 2,4-D - 2,4-Dichlorophenoxyacetic acid IPC - Ammonium salt of Isopropyl N-phenol carbamate MCP - 2 methyl-4-chlorophenoxyacetic acid PCP - Sodium pentachlorophenate DNOSBP- Ammonium salt of dinitro-0-secondary butyl phenol 22. infested piece of turf. Grasses present were couch grass, Agropyron repens, Kentucky hluegrass, Poa pratensis, and a scattering of other miscellaneous grasses. These plots provided a more extreme grass and weed condition than would normally be encountered in a strawberry plantation. The potential herbicidal value of these sprays could be best determined under such conditions. The plots were treated as shown i n table 2. Heavy rains followed within 12 hours after applications of treatments 1, 2, 3 and 4. A l l sprays were applied with a knapsack sprayer. General notes were taken periodically following the applications and the effect of the sprays upon the grass and weed growth recorded. RESULTS Extraots from the general notes taken on June 1 are as follows: Treatment 1 (TCA) - at 25 pounds per acre - no apparent effect. - at 40 pounds per acre - slight browning of the grass. - at 80 pounds per acre - browning of the grass slightly more than 40 pounds. - at 100 pounds per acre - appeared the same as the 80 pound treatment. - at 200 pounds per acre - appeared to be hitting 23. dandelion, plantain, etc., more severely than the lower concentrations. The grass was only slightly browner than in the plots of lower concentrations. Treatment 2 (TCA plus 2.4-D) - at 40 pounds per acre plus 2,4-D - browning of grass and marginal browning of broad-leaved weeds. Some curling of plantain leaves. - at 100 pounds per acre plus 2,4-D - There appeared to be less browning of the grass foliage as compared to 50 pounds per acre plus 2,4-D. Treatment 5 (IPC) - no apparent effect from any of the concentrations on the grass or the weeds. Treatment 4 (IPC plus 2.4-D) - a l l concentrations show slight 2,4-D effect on broad-leaved weeds, but no effect apparent on the grass. Further notes were taken on June 17, extracts of which follow: Treatment 1 (TCA) - at 40 pounds per acre grass slightly burned and as the concentration increases burning of grass increases u n t i l at 200 pounds per acre some of the grass i s definitely dead. Treatment 2 (TCA plus 2.4-D) - at 40 pounds per acre plus 2,4-D - plantain dying, dandelion showing effects, grass browning. 24. - at 100 pounds per acre plus 2,4-D 1000 ppm as above but damage more severe. Treatment 5 (IPC) - no apparent effect from any of the concentrations on the grass or weeds. Treatment 4 (IPC plus 2.4-D) - only 2,4-D effect on broad-leaved weeds apparent. Treatment 5 (MCP) - l i t t l e effect on the grass. Treatment 6 (PCP) - grass showed browning. Treatment 7 (DNOSBP) - grass showed some browning. An extract from notes taken on June SO follows: Treatments 5 & 4 (IPC & IPC plus 2.4-D) - a l l plots at this time were showing the following effects: grass stunted and browned; broad-leaved weeds showed typical 2,4-D damage. A f i n a l survey was made of a l l the plots on August 1. and brief extracts follow: Treatment 1 (TCA) - in a l l plots treated with TCA above 25 pounds per acre a l l grasses appeared dead. The broad-leaved weeds, however, spread rapidly. Treatment 2 (TCA plus 2.4-D) - This treatment i n addition, to k i l l i n g the grass 25. also controlled the broad-leaved weeds to a degree — plantain appeared to be completely eradicated, whereas the well established dandelion and yellow cress showed recovery. Treatments 3 & 4 (IPC & IPC pins 2.4-D) - In a l l plots, grasses were pa r t i a l l y k i l l e d and stunted. Broad-leaved weeds were growing i n a l l plots, but to a lesser extent i n plots treated with IPC plus 2,4-D. Treatments 5. 6 & 7 (MCP. PCP & DNOSBP) - Plots treated with these chemicals a l l showed partial and stunting of the grass. DISCUSSION From the above results i t i s apparent that TCA w i l l effectively control well established couch grass, Kentucky bluegrass and other grasses i f applied at 40 pounds per acre. TCA plus 2,4-D appears promising as a weedicide for land infested with both perennial grasses and broad-leaved weeds. Carlson and Moulton (5) report that both ammonium and sodium salts of trichloroacetate (TCA) gave slow but effective control of couch grass and Kentucky bluegrass under greenhouse conditions, i f applied at the rates of 150 - 200 pounds per acre i n the case of well established grass and 40 - 80 pounds per acre i n the case of young growth. 26. Barrons (1) obtained good k i l l s of couch grass from as l i t t l e as 40 pounds per acre. In this experiment IPC required approximately a month before effect upon the grass was apparent. However, as seen from the results IPG f i n a l l y gave a f a i r l y effective control of the grasses present though not as absolute a control as was obtained from TCA. Broad-leaved weeds were apparently not harmed except i n those plots to which 2,4-D had been added. Lachman (14) found that IPC was valuable as a selective herbicide i n that i t effectively k i l l s grasses with l i t t l e or no harm to broad-leaved plants. Mitchell and Marth (16) report that when IPC was applied at relatively high rates (50 and 100 pounds per acre) to potted s o i l in which crab grass had become established and had developed leaves extending about 1 - 2 cm. above the surface of the s o i l , the plants failed to grow further and died within a period of two weeks following treatment. In light of the results obtained i n Experiment 1 i t would appear that a suitable combination of IPC and 2,4-D should offer promise as a weed-killer i n plantations of actively growing British Sovereign strawberries where weeds and grasses are p l e n t i f u l . PCP, MCP and DNOSBP gave no better control of grasses than did IPC under conditions of this experiment. Since the results of Experiment 1 show they cause considerable 27 . harm to a c t i v e l y growing B r i t i s h Sovereign plants i t can be concluded that they offer l i t t l e promise as weedicides for strawberries during the growing period. CONCLUSIONS Of the various herbicides tested i n t h i s exploratory experiment i t appears that IPC plus 2,4-D offers the greatest promise as a selective weedicide f or B r i t i s h Sovereign strawberries during the growing period i n planta- tions where both broad-leaved weeds and grasses are p l e n t i f u l . EXPERIMENT I I I Object: To determine the effe c t of various concentrations of the more promising herbicides (as previously determined from Experiments I and I I ) on newly germinated grass seedlings. Materials and Methods: Plots one square foot i n area were l a i d out i n f l a t s i n the greenhouse and sown to perennial rye grass on June 8. The following treatments were applied on June 20 at which time the grass was 2^ inches t a l l . 28 Treatment No. Material Bate/acre 1. PCP 10 lbs. 2. IPC 10,40 & 80 lbs. (as a spray) 3. IPC 40 & 80 lbs. (as a dust with sand) 4. IPC plus 2,4-D 40 lbs. 1000 ppm 5. Untreated Note: PCP - Sodium pentachlorophenate IPC - Ammonium salt of Isopropyl N-phenol carbamate General notes were taken periodically following treatments and the effect of the sprays upon the grass recorded. RESULTS A f i n a l survey of the f l a t s was made on July 18. and cpmplete notes taken. Extracts from these notes follow: Treatment 1 (PCP) - partial k i l l and stunting of the grass. 8 9 . Treatment 8 (IPC) - at 10 pounds per acre - partial k i l l and stunting of the grass. - at 40 pounds per acre - partial k i l l and stunting. - at 80 pounds per acre - complete k i l l . Treatment 5 (IPC dust) - at both 40 and 80 pounds per acre - oomplete k i l l . Treatment 4 (IPC plus 2.4-D) - partial k i l l and stunting. DISCUSSION From an examination of the above results i t i s seen that 40 pounds of IPC in sand gave complete k i l l of the perennial rye grass whereas only partial k i l l and stunting was obtained from 40 pounds of IPC in water; this may be due to the greater residual effect of dust. There was l i t t l e difference i n effect upon the grass between IPC (spray) at 10 pounds, 40 pounds or 40 pounds per acre plus 2,4-D. But IPC at 80 pounds per acre gave complete k i l l . Thus i t would appear that the higher concentrations are required when IPC i s applied as a spray. Mitchell and Marth (16) found that IPC i s inactivated i n the presence of moist, f e r t i l e s o i l . PGP at 10 pounds per acre gave only partial k i l l and stunting. Therefore, i t appears to be no better than IPC at 10 pounds per acre for k i l l i n g perennial rye grass seedlings 30. and further from Experiment 1 i t was shown that PCP was detrimental to the strawberry plants at higher concentrations. IPC would appear, therefore, to be the most promising herbicide for the control of grasses i n strawberries. CONCLUSIONS Further experimentation i s required to determine the most effective combination of IPC and 2,4-D for use as a selective herbicide for British Sovereign strawberries. EXPERIMENT IV Object: To study the effects of various combinations and concentrations of 2,4-D and IPC and other promising herbicides on several kinds of newly germinated grass seedlings and British Sovereign strawberry plants i n the greenhouse. Materials and Methods: Grass Seedlings Three randomized blocks were la i d out on the green- house benches. Each block consisted of 23 f l a t s so that one f l a t constituted a plot. Each f l a t was 4 inches deep and 1 foot wide by l£ feet long. One blck of f l a t s was f i l l e d 31. with composted s o i l while the f l a t s of the other two blocks were f i l l e d with garden s o i l (sandy loam). On August 18, 1949, the 69 f l a t s were sown with the following grasses: creeping red fescue (Festuoa rubra; perennial rye (Lolium perenne); orchard (Dactylis glomerata) and hog millet (Panicum miliaceumi. Thus each f l a t contained the four species of grass seed sown so that each specie was in a separate band 4& inches wide across the f l a t . Therefore, the effect of the various treat- ments upon each specie of grass could be easily studied. British Sovereign strawberry plants were l i f t e d from the f i e l d and planted i n oomposted s o i l contained i n t i n pots 7 inches i n diameter and 8 inches deep, with bottom drainage. The pots were then arranged i n three randomized blocks on the greenhouse benohes so that one pot constituted a plot (see figure 1 for general layout). Treatments: Both the grass seedlings and the strawberry plants were given the following treatments: Strawberry Plants On August 18, 1949, sixty-nine uniform, young, Treatment Ho. Material and Rates 1 2 - 6 ^ l b . 2,4-D per acre. & l b . 2,4-D plus 10,20,40, 60 and 80 lbs. IPC per acre. 7 1 l b . 2,4-D per acre. 32. 8 - 1 2 1 l b . 2,4-D plus 10,20,40 60 & 80 lbs. IPC per acre. 13 2 lbs. 2,4-D per acre. 1 4 - 1 8 2 lbs. 2,4-D plus 10,20,40, 60 & 80 lbs. IPC per acre. 19 75 gal. per acre of emulsifiable Pentachlorophenol. 20 150 gal. per acre of emulslfiable Pentachlorophenol. 21 1$ aero oyanate 22 Z% aero cyanate 23 Untreated Note: 2,4-D — Sodium salt of 2,4-Diehlorophenoxyaeetic acid. (Dow-Deweed). IPC — Ammonium salt of Isopropyl N-phenol carba- mate. Aero-cyanate — 91$ potassium cyanate prepared by American Cyanamide Co. Emulslfiable pentachlorophenol — oil-in-water. emulsion of pentachlorophenol prepared by Monsanto Chemical Co. On August 30 a l l treatments were applied with a hand sprayer of one-pint capacity. Cardboard shields were held along the sides of each area being sprayed to avoid d r i f t of the mixture (See figure 2.) General notes, measurements and photographs were taken periodically following the applications and the effect of the sprays upon the various species of grasses and straw- berry plants noted. 33. Figure 1 - General View Showing the Layout of the Plot s i n the Greenhouse. 3 4 . Figure 2 - Method of Spraying Greenhouse Plots. Note the Cardboard Shields held along the sides of each area being sprayed to avoid d r i f t of the mixture. 35. RESULTS Twelve days following application of the treatments the height of the Hog Millet was recorded. These were the only measurements made at this time since the Hog Millet appeared to he representative of the effects of the treatments on a l l the grasses. These measurements are shown i n table 3 and figure 3. On October 30, (two months after sprays had been applied) the grasses remaining were harvested (by clipping at the s o i l level) and weighed* The clipping results are presented i n table 4 and i n figures 6, 7, 8 and 9. A complete s t a t i s t i c a l analysis of the results was made. However, only minimum significant differences at the •05 level w i l l be shown here, but the complete analysis w i l l be found in the appendix. The treatment heights (from table 3) are li s t e d below in descending order and entered alongside each i s the amount of the difference from the previous value (M.S.D. 1.08). Treatment Mean Height Difference (cms) from pre v. value. 23 - Untreated 14.3 2 - &lb. 2,4-D + 101b. IPC 12.7 1.6 1 - is l b . 2,4-D 12.3 0.4 8 - 1 l b . 2,4-D + 101b. IPC 11.7 0.6 Table 3 - The Height of Hog Millet at Twelve Days following the Treatments. (1949) 36, Treatment No. Treatments (per acre) Mean Height (cms) 1. £ l b . 2,4-D 12.3 2. £ l b . 2,4-D + 10 lbs. I P C 12.7 3. £ l b . 2,4-D 20 lbs. I P C 11.3 4. £ l b . 2,4-D * 40 lbs. I P C 10.7 5. £ 2,4-D + 60 lbs. I P C 10.0 6. £ l b . 2,4-D + 80 lbs. I P C 8.3 7. l l b . 2,4-D - 11.3 8. l l b . 2,4-D + 10 lbs. I P C 11.7 9. l l b . 2,4-D + 20 lbs. I P C 10.3 10. l l b . 2,4-D 40 lbs. I P C 9.0 11. I l b . 2,4-D 60 lbs. I P B 8.0 12. I l b . 2,4-D 80 lbs. I P C 7.7 13. 2 l b . 2,4*D 9.0 14. 2 l b . 2,4-D 10 lbs. I P C 11.7 15. 2 lb. 2,4-D 4 20 lbs. I P C 8.3 16. 2 l b . 2,4-D + 40 lbs. I P C 7.7 17. 2 lb. 2,4-D + 60 lbs. I P C 7.3 18. 2 l b . 2,4-D + 80 lbs. I P C 5.7 19. 75 gal. Pentachlorophenol 0.3 20. 150 gal. Pentachlorophenol 1*7 21. 1 <fo aero cyanate 3.0 22. 2 $ aero cyanate 3.7 23. Untreated 14.3 ~" M.S.D. » 1 .08 cms. ^ for treatments (.05 level) 37. s • 1 • « n IPC i n pounds per acre Figure 3 - Effect of Applications of Various Amounts of 2,4-D and Mixtures of 2,4-D and IPC on the Height of Hog Millet (Panicum miliaceum) as at September 11, 1949. 3 8 . 1 4 mm 2 I D . 2 , 4 - D 1 0 l b . IPC 1 1 . 7 0 # 0 3 k l b . 2 , 4 - D + 2 0 l b . IPC 1 1 . 3 0 . 4 7 - 1 l b . 2 , 4 - D 1 1 . 3 0 . 0 4 - * l b . 2 , 4 - D + 4 0 l b . IPC 1 0 . 7 0 . 6 9 - l l b . 2 , 4 - D * 2 0 l b . IPC 1 0 . 3 0 . 4 5 - * l b . 2 , 4 - D • 6 0 l b . IPC 1 0 . 0 0 . 3 1 0 - l l b . 2 , 4 - D 4 0 l b . IPC 9 . 0 1 . 0 1 3 - 2 l b . 2 , 4 - D 9 . 0 0 . 0 6 mm * l b . 2 , 4 - D • 8 0 l b . IPC 8 . 3 0 . 7 1 5 - 2 l b . 2 , 4 - D + 20 l b . IPC 8 . 3 0 . 0 1 1 - 1 l b . 2 , 4 - D 60 lb. IPC 8 . 0 0 . 3 1 2 - 1 l b . 2 , 4 - D + 8 0 l b . IPC 7 . 7 0 . 3 1 6 - 2 l b . 2 , 4 - D * 4 0 l b . IPC 7 . 7 0 . 0 1 7 - 2 l b . 2 , 4 - D 6 0 l b . IPC 7 . 3 0 . 4 1 8 - 2 l b . 2 , 4 - D 8 0 l b . IPC 5 . 7 1 . 6 2 2 - 25 % aero oyanate 3 . 7 2 . 0 21 - 1? I aero cyanate 3 . 0 0 . 7 20 - 1 5 0 gal. Pentaehlorophenol 1 . 7 1 . 3 1 9 - 7 5 gal. Pentachlorophenol 0 . 3 1 . 4 Now any difference or cumulative difference greater than 1 . 0 8 the M.S.D. proves a significant decrease in height (repression of growth) over treatments higher up on the l i s t . On this basis, treatment 1 9 i s significantly better than any of the treatments. It follows that treatments 2 0 , 2 1 , and 2 2 i n that order are significantly better than any of the remaining treatments. However, these treatments severely 39. damaged the strawberry plants (see figure 4) and thus are of no value as selective herbicides for actively growing strawberry plants. The remaining treatments (2,4-D and 2,4-D • IPC) caused no apparent damage to the strawberry plants and thus can be considered. Now i f the above l i s t i s studied along with figure 3 i t w i l l be noted that treatment 18 i s significantly better than any other of the remaining treat- ments. There i s no significant difference between treatments 17, 16, 12, 11, 15 or 6. However, treatments, 17, 16 and 12 are a l l significantly better than treatment 13 (see figure 5). There i s no significant difference between treatment 13 or 5. But treatment 13 i s significantly better than treatment 9. There i s no significant difference between treatments 9, 4 and 7. Treatment 9 i s significantly better than treatment 14. There i s no significant difference between treatments 7, 3, 14, 8 and 1. Treatments 7 and 3 are significantly better than treatment 2. Finally, treatment 2 i s significantly better than treatment 23. It i s also noted from the above l i s t and figure 3 that the addition of only 10 pounds IPC to 2,4-D has a reverse effect i.e., i n a l l cases 10 pounds of IPC caused an increase in the height of the millet over those treated with 2,4-D alone. Almost 20 pounds of IPC i s required to increase the effeot of 2,4-D. With each additional increase in IPC the growth i s further repressed. 40. Figure 4 - The Ef f e c t of Pentaehlorophenol and Potassium Cyanate upon B r i t i s h Sovereign Strawberry Plants and Grass Seedlings as at Sept. 6, 1949. The numbers ref e r to treatments as follows: No, 21 - 1% Aero Cyanate No. 23 - Untreated No. 19 - 75 g a l . per acre of emulsifiable pentaehlorophenol. 41 Figure 5 - The Effect of 2,4-D and 2,4-D plus IPC upon the various Grasses as at Sept. 11, 1949. The Numbers refer to treatments as follows: No. 23 - Untreated No. 13 - 2 l b s . 2,4-D per acre No. 1 8 - 2 l b s . 2,4-D plus 80 l b s . IPC per acre. 42. A l l plots were harvested two months after treatments were applied. The clippings from each specie of grass i n each plot were weighed and the weights recorded. The results are summarized i n table 4 and figures 6, 7, 8 and 9. Creeping red fescue (Festuea rubra) An examination of table 4 and figure 6 shows that an application of k pound 2,4-D per acre caused a significant increase in weight of clippings over the untreated plot. There i s no significant difference between treatment 7 (1 pound 2,4-D) and the unsprayed plot. However, 2 pounds 2,4-D per acre did cause a significant reduction i n the grass as oompared to the untreated plot. The addition of IPC further reduced the amount of grass. In general this reduction i n grass increases with an increase i n IPC. However, i t w i l l be noted especially for the mixtures containing i pound 2,4-D and 2 pounds 2,4-D that there i s only a slight difference between the mixture containing 40, 60 and 80 pounds of IPC per acre. Perennial rye grass (Lolium perenne) An examination of table 4 and figure 7 shows that both £ pound 2,4-D and 1 pound 2,4-D per acre very s i g n i f i - cantly increased the amount of grass i n comparison with the unsprayed plots. No significant difference was found between the plots sprayed with 2 pounds 2,4-D per acre and the unsprayed plots. In general the amount of grass present 43. , Table 4 - The amount of grass remaining one month after treatments were applied (weight of elippings). Grasses Creeping Perennial Orchard Hog red fescue rye grass millet (Festuca rubra)(Lolium perenne) (Daetylis (Pan!cum glomerata) miliaceum) Treatments Mean weight in grams 1. 10.1 26.7 13.8 34.7 2. 5.3 13.7 12.3 48.7 3. 2.5 3.8 5.0 43.8 4. 2.2 4.7 2.8 45.7 5. 1.5 4.0 1.7 51.7 6. 1.5 4.0 1.7 55.3 7. 8.8 26.8 10.5 36.8 8. 4.0 10.7 6.3 45.7 9. 5.8 15.7 6.8 34.0 10. 3.8 7.7 2.8 41.7 11. 2.7 4.7 2.3 26.5 12. 1.7 4.3 1.7 39.5 13. 6.2 15.5 6.7 36.2 14. 5.0 14.2 6.5 29.7 15. 3.7 12.5 6.2 29.0 16. 2 • 2 5.7 2.3 30.0 17. 1.8 6.8 2.2 33.7 18. 1.7 3.8 1.5 23.5 19. 8.7 28.7 5.7 1.5 20. 3.8 13.0 1.7 9.2 21. 8.0 11.7 10.0 12.3 22 • 9.0 18.4 18.0 14.3 23. 9.2 15.7 12.7 44.5 M.S.D. (.05 level) 0.5 3.7 2.8 6.9 (gms) 44 O IO i o l/o 6" *<> IPC i n pounds per acre Figure 6 - Effect of Applications of,Various Amounts of 2,4-D and Mixtures of 2,4-D and IPC on the weight of Clippings from Creeping Red Fescue (Festuca rubra) as at Sept. 30, 1949. {M.S.D. at .05 le v e l » 0.5) 45 o 'o zo vo Y& IPC in pounds per acre Figure 7 - Effect of Applications of Various Amounts of 2,4-D and Mixtures of 2,4-D and IPC on the weight of Clippings from Perennial Rye Grass (Lolium perenne) as at Sept. 30, 1949. (M.S.D. at .05 level = 3.7) 46. O '0 2c fa *>" T o IPC in pounds per acre Figure 8 - Effect of Applications of Various Amounts of 2,4-D and Mixtures of 2,4-D and IPC on the weight of Clippings from Orohard Grass (Dactylis glomerata) as at Sept. 30, 1949. (M.S.D.c at .05 level - 2.8) 47. IPC i n pounds per acre Figure 9 - Effect of Applications of Various Amounts of 2,4-D and Mixtures of 2,4-D and IPC on the weight of Clippings from Hog Millet (Panicum miliaceum), as at Sept. 30, 1949. M.S.D. at .05 level = 6.9) 48. was directly related to the concentration of IPC* However, as with the fescue there i s l i t t l e difference between the plots sprayed with mixtures containing 40, 60 or.80 pounds of IPC. Orchard grass (Dactylis glomerata) An examination of table 4 and figure 8, shows that § pound 2,4-D increased the amount of grass slightly as compared to the unsprayed plot. There i s no significant difference between treatment 7 (1 pound 2,4-D) and the unsprayed plots. However, 2 pound 2,4-D per acre gave a significant reduction in the amount of grass present as com- pared to the unsprayed plots. As i n the above two grasses the addition of IPC oaused a decrease i n the amount of grass present. It i s also noted that there i s no significant difference between the treatments containing £ pound 2,4-D plus 40, 60 or 80 pounds IPC; 1 pound 2,4-D plus 40, 60 or 80 pounds IPC; or 2 pounds 2,4-D plus 40, 60, or 80 pounds IPC. Hog millet (Panioum miliaoeum) On examination of table 4 and figure 9 i t w i l l be noted that the i , 1 and 2 pounds 2,4-D per acre a l l oaused a significant reduction in the millet as compared to the un- sprayed plots. However, there i s no significant difference between the three concentrations of 2,4-D. Again as pointed out previously re: figure 3 (height of millet) the treatments containing -§• pound and 1 pound of 2,4-D plus 10 pounds IPC 49. per acre caused an increase i n the weight of clippings as compared to the untreated plots, however, this increase i s not significantly greater than the unsprayed plots. It i s also noted that plots treated with a mixture of h pound 2,4-D plus IPC tend to increase tn weight of clippings with concentration of IPC, this result i s i n direct reverse to that obtained by the same mixtures with the other grasses. The resuits of plots treated with 1 pound 2,4-D per acre plus IPC have no definite trend and with the exception of 60 pounds IPC no mixture i s better than the 1 pound of 2,4-D alone. The treatments containing 2 pounds 2,4-D a l l gave a significant reduction i n weight of clippings. There i s no significant difference between 2 pounds 2,4-D alone and 2 pounds 2,4-D plus 10, 20, 40 and 60 pounds IPC per acre. There i s , however, a significant difference between 2 pounds 2,4-D alone and 2 pounds 2,4-D plus 80 pounds IPC per acre. Effect on Strawberry Plants The treatments consisting of 2,4-D or of 2,4-D plus IPC caused no apparent detrimental effects to the strawberry plants. However, treatments 19 and 20 (Pentaehlorophenol) caused excess burning and f i n a l l y death to the plants. Treatments 21 and 22 (Aero cyanate) caused marginal burning of the leaves and f i n a l l y complete browning, but the crowns were not k i l l e d as i n the pentaehlorophenol treatments. See figure 4 showing the effects of treatments 19, 21 and 23 on the strawberry plants and grasses. 50. DISCUSSION i t This experiment was designed to study the various combinations and concentrations of 2,4-D, IPC and other promising herbicides on several kinds of newly germinated gravs seedlings and British Sovereign strawberry plants i n the greenhouse. An examination of figure 3 and table 3 om the effects of 2,4-D and various mixtures of 2,4-D and IPC on the height of Hog Millet twelve days after the application of the treatments shows that 2,4-D alone caused a significant decrease i n height and that this stunting increased with Increase in the concentration of 2,4-D. At this time a l l the grasses present (Creeping red fescue, Perennial rye grass Orchard grass) appeared to respond i n the same manner. Mitchell and Earth (15) obtained somewhat similar results. They found that the growth of well-established creeping bentgrass was depressed by spraying with a water mixture of 2,4-D at rates equivalent to £, l£, 2 i and 3 pound of the acid per acre. Plants sprayed at rates equivalent to £ and l£ pounds per acre recovered during a period of 3-4 months following treatment. Further from table 3 and figure 3 i t i s noted that the addition of only 10 pounds of IPC in a l l oases caused an increase i n the height of the grass over those treated with 2,4-D alone. It would appear at this point that 10 pounds of 51. IPC had a slight inactivating effect upon the 2,4-D. However, even this mixture resulted i n a significant suppression of growth of the grass as compared to the untreated plots. Almost 20 pounds of IPC are required before this inactivating effect i s overcome and the mixture of 2,4-D and IPC i s made more effective than the 2,4-D alone. With each additional increase i n IPC stunting i s further increased. The mixture containing 2 pounds 2,4-D and 80 pounds of IPC per acre was significantly better than any of the other 2,4-D and 2,4-D plus IPC mixtures. It i s interesting to note that there i s no significant difference between treatments 6, 11, 12, 15, 16 and 17 (i.e. h pound 2,4-D plus 60 pounds IPC, 1 pound 2,4-D plus 60 pounds IPC, 1 pound 2,4-D plus 80 pounds IPC, 2 pounds 2,4-D plus 20 pounds IPC, 2 pounds 2,4-D plus 40 pounds IPC, and 2 pounds 2,4-D plus 60 pounds IPC) and these treatments are second best. There appears to be a tendency towards definite optimum combinations of 2,4-D and IPC. From these results and using the above combinations the following generality appears feasible: beginning with % pound 2,4-D plus 80 pounds IPC we may say that as the IPC i s reduced by 20 pounds i t i s necessary to double the amount of 2,4-D to obtain the same effects i.e., X pound 2,4-D plus 60 pounds IPC or 2 pounds 2,4-D plus 40 pounds IPC gives the same effects as h pound 2,4-D plus 80 pounds IPC. Therefore, i t would appear that both chemicals have a supplementing value for one another i n the depressing of grass growth. Such a relationship i s of value for i t means that the herbioidal 52. effect of 2,4-D can be supplemented with IPC and at the same time reduce the injurious effeot of 2,4-D on crop plants. On examination of table 4 and figures 6, 7, 8 and 9, on the weight of clippings of the various grasses one month after treatments were applied i t i s readily seen that the various grasses responded somewhat differently from one another. An application of £ pound of 2,4-D per acre to Creeping red fescue caused a significant increase in weight of clippings over the unsprayed plot. It took 2 pounds of 2,4-D to significantly decrease the weight. Both the £ pound 2,4-D and the 1 pound 2,4-D per acre to perennial rye grass caused very significant increases in weight of clippings over the unsprayed plot. The 2 pounds 2,4-D was not significantly different from the unsprayed plot whereas i n the orchard grass there was no significant differences in weight of clippings between the plots sprayed with £ pound 2,4-D or 1 pound 2,4-D and the unsprayed plot. But 2 pounds of 2,4-D reduced the weight of clippings significantly. In the case of the millet i t i s noted that the § pound, 1 pound and 2 pounds of 2,4-D per acre a l l caused a significant reduction in the clipping weight of millet as compared to the unsprayed plots. The increases in growth over the unsprayed plots, as noted in creeping red fescue and perennial rye grass when lesser amounts of 2,4-D are used, may be due i n part to the elimination of weed competition in the sprayed plots. 5 3 . Mitchell and Marth (15) sprayed a water mixture containing 0.1$ 2,4-D and 0.5% Carbowax 1500 at rates equivalent to £, 1&, 2£ and 3 pounds of acid per acre on potted s o i l i n which Kentucky blue-grass, redtop, and creeping red fescue grass seeds had been planted. The treatments reduced the number of redtop seedlings that appeared by 28, 83, 83, and 95$ respectively. A sli g h t l y greater number of fescue seedlings emerged from the s o i l sprayed at rates equivalent to £ and l£ pounds of acid per acre, while the heavier applica- tions reduced emergence by 10 and 17%, i n comparison with the unsprayed s o i l . Fourteen per cent more bluegrass seedlings appeared i n the s o i l sprayed at a rate equivalent to £ of a pound per acre than emerged in the unsprayed s o i l . The heavier applications reduced the emergence of bluegrass by as much as 32% below that of the untreated s o i l . In general the addition of IPC to the plots contain- ing the perennial grasses reduced the weight of clippings and this reduction increased with concentration of IPC. From figures 6, 7, 8 and 9 i t i s seen that the curves tend to level out from 40 pounds of IPC on. Thus 40 pounds of IPC in the mix appears to be the most practical; i t depresses the growth of grass almost as completely as do the higher concentrations of 60 and 80 pounds per acre. Also, i t must be mentioned at this point that concentrations of IPC over 40 pounds per acre at the usual rates of application tend to precipitate and clog the spray nozzle. Lachman (14) also had 54. the same trouble he states that the solubility of IPC i s only about 250 p.p.m. and i s only attained after vigorous shaking or s t i r r i n g . He has found that IPC i s readily soluble i n Carbowax 1500, ethyl alcohol, isopropyl alcohol, acetone, and glacial acetic acid and as cosolvents thSse oompounds are helpful i n attaining the maximum concentration i n a shorter time. However, i n concentrations greater than 250 p.p.m. the IPC i s precipitated upon the addition of water to the IPC and solvent. Doxey (7) studying the effect of IPC on mitosis in rye and onion found that 200 p.p.m. solution closely approached saturation. The chemical companies have recognised this problem and are developing more soluble forms of IPC. From table 4 and figure 9 i t i s seen that the response of annual hog millet to 2,4-D and mixture of 2,4-D and IPC i s quite different from that obtained i n the perennial grasses. As mentioned earlier, even the lesser concentrations of 2,4-D alone significantly depressed the growth i n comparison with the unsprayed plot. There was no significant difference between the three concentrations of 2,4-D. Again, i n the case of £ pound 2,4-D and 1 pound 2,4-D the addition of 10 pounds IPC appears to inactivate the 2,4-D. The millet appeared to more or less recover from the mixtures of 2,4-D and IPC, especially was this true with the lesser amounts of 2,4-D. In general though, as the concentration of the 2,4-D was increased the greater was the depression of growth. The 2,4-D at the concentration of 2 pounds per acre 55. i s only made slightly more effective with the addition of IPC. Although these plots are significantly different from the unsprayed plots, the results are not too satisfactory since the control i s only about 50% as compared to 80 and 90% con- t r o l obtained with the perennial grasses. Differences in the sensitivity of grasses to IPC were also noted by Mitchell and Marth (16) who found that when crabgrass and bluegrass seeds were planted i n s o i l con- taining known amounts of IPC that emergence of bluegrass seedlings was greatly reduced in s o i l that contained as l i t t l e as 3.4 mg. of IPC per pound of s o i l , while the emergence percentage for crab grass (Digitaria sanguinalis) increased with the addition of IPC to the s o i l . Although the emergence percentage of par t i a l l y dormant crab grass was apparently stimulated by IPC i n this experiment, the subsequent growth of the plants was greatly inhibited. Mitchell and Marth (16) studied the sensitivity of several other monocotyledonous plants and have constructed a table showing the sensitivity of these plants to IPC. This table has been reproduced here (see table 5). An examination of table 5 shows that rye grass, red top, and orchard grass are a l l very sensitive to IPC while millet i s only slightly sensitive. Thus these results atie confirmed by those obtained by the writer. Th<y further add that the effeot of IPC when applied at the rates of 30-60 pounds per acre on the growth of less 56. sensitive species (sorghum, Sudan grass) was prolonged so that plants grew above the surface of the s o i l for a distance of 1-3 cm. and then failed to develop further. Microscopic examination revealed that these plants remained alive but stunted after appearing above the surface. These stunted plants failed to produce seeds. As an Experiment 1, 2,4-D and 2,4-D plus IPC apparently did not cause any detrimental effeots to the straw- berry plants. Such was not the case with pentaehlorophenol and potassium cyanate. Pentaehlorophenol caused excess burning and death while cyanate caused considerable marginal browning of the leaves though i t did not appear to harm the strawberry crown. Therefore though these chemicals gave excellent control of the grass they are, however, of no use as weedicides for strawberries during the growing season. CONCLUSIONS The results of this experiment which was la i d out in the greenhouse using mixtures of three levels of 2,4-D and five levels of IPC, two levels PCP and two levels of cyanate on four species of grass and British Sovereign strawberries shows that: 1. There i s considerable difference in sensitivity between the different species of grass to 2,4-D and IPC. 57. Table 5 - Sensitivity of some Monoootyledonous Plants to IPC when Applied to the Soil at a Rate Equivalent to 5 pounds per acre, (after Mitchell and Marth) Plant Emergence Index Plant Emergence Index Bermuda grass Amber sorghum Sudan grass Millet Bluegrass Barley 130 99 88 86 4 0 Fescue Ryegrass Red top Timothy Orchard grass Quack grass 0 0 0 0 0 0 values represent relative emergence from seeds planted i n treated s o i l calculated on the basis that emergence in comparable untreated s o i l equalled 100 per cent. 58. 2. A mixture of 2 pounds of 2,4-D and 40 pounds of IPC per acre gives very satisfactory control of perennial rye grass, Creeping red fescue, and orchard grass ( a l l perennial grasses) but not of the annual hog millet. 3. Mixtures of 2 pounds of 2,4-D and up to 80 pounds of IPC per acre apparently did not cause any detrimental effects to the Br i t i s h Sovereign strawberry plants. 4. Pentachlorophenate and potassium cyanate are not suitable herbicides for strawberries during the growing season. The pentachlorophenate caused extreme burning and f i n a l l y death. The cyanate, however, only caused marginal to severe browning, but apparently did not injure the crown and, therefore, may be of value as an after harvest or dormant spray. EXPERIMENT 7 Object;- To-study the effect of various concentrations of 2,4-D and 2,4-D supplemented with IPC on both weeds and British Sovereign strawberry plants under f i e l d conditions. Materials and Methods; Plots 18£* x 21* were l a i d out in three randomized blocks. Strawberries were planted i n rows 3g feet apart and 18 inches between plants. Young, certified, British Sovereign plants were planted out in the spring of 1949. Note: 59. The treatments were as follows: 1. 1 l b . 2,4-D per acre. 2. 2 lbs. 2,4-D per acre. 3. 3 lbs. 2,4-D per acre. 4. 4 lbs. 2,4-D per acre. 5. 2 lbs. 2,4-D plus 40 lbs. IPC per acre. 6 . Hand weeded. The amounts of 2,4-D refer to acid equivalent. Treatments were to have been applied to the young plants as weed growth dictated possibly three or four times during the season. However, the f i r s t application was delayed due to rainy weather u n t i l July 2, and consequently the i weeds were 7-8 inches t a l l and very dense. Both a knapsack sprayer and a Hudson sprayer were used in applying the f i r s t application of sprays. See figure 10 for general layout of experiment and method of applying sprays. Temperature recorded was 68.5°P. Soil samples were taken of the area to be sprayed before the f i r s t application. The results of the analysis appear i n table 6. General notes, measurements and photographs were taken periodically follow- ing the applications of treatments on the following: 1. Weed control, effects on various species noted. 2. Effects on strawberry plants noted. Table 6 - Soil Analysis of Strawberry Plots Obtained by Spurway Chemical Tests, Ppm. Lb. a/6 in. Remarks Nitrates 10 80 Mediumi Phosphorus k 4 Low Potassium 3 24 Low Calcium 40 320 Low Magnesium 1 8 Low Reaction pH 6.0 61. 3, Plant growth measured by leaf counts, runner counts, and observation ratings. F e r t i l i z e r (4-10-10) was broadcasted alongside of the rows on July 4 at 700 pounds per acre. A second application of f e r t i l i z e r was made on August 1, at the same rate. On July 29, after notes had been taken on weed control, etc., a l l plots were hoed and raked off. Leaf counts and growth ratings were taken on September 1. Second application of sprays was applied on September 1, with a knapsack sprayer. A l l materials were applied at the rate of 100 gallons of solution per acre. Temperature recorded at this time was 78°F. RESULTS Control of Various Weed Species: The various weed species present in the strawberry plots and their approximate percentage at time of spraying were as follows: Polygonum Persicaria L. (Lady's Thunb) .. 60-65%. Chenopodium album L. (Lamb's Quarters) .. 10%. Spergula arvensis L. (Corn Spurrey) 10%. Eohinochloa crusgalli (L) Beaux (Wild Millet) ..10%. A l l other weeds combined made less than 10 per cent of the total weed population. They are li s t e d below: 62. Roripa polustrla (L) Bess. (Yellow Cress) Amaranthus retroflexus L. (Red-root Pigweed) Convolvulus arvensis L. (Field Bindweed) Agropyron repens (L) Beauv. (Couch Grass) Rapjranus Raphanistrum L. (Wild Radish) Rumex Acetosella L. (Sheep Sorrel) Gnaphalium uliginosum (Cudweed) Following are extracts of notes taken on the effect of the treatments on the weeds: July 2 - Curling of leaves of weeds noticeable within an hour after spraying even with 1 pound per acre of 2,4-D. July 4 ( 2 flays following sprays) - A l l weeds showing typical 2,4-D injury such as curling of leaves, twisting and curling of petioles. Treatment 5 (2 l b . 2,4-D plus IPC) - no effect of IPC on grass as yet - 2,4-D injury as i n other plots. July 8 (6 days following sprays) Treatment 5 (2 lbs. 2,4-D plus IPC) - Weeds browning more than in other plots. - Wild radish practically dead. 63. - Field Bindweed - browned. - Lady's Thumb - browned. Treatment 4 (4 lbs. 2,4-D) - Some browning, but not near as noticeable as Treatment 5 — more of a yellowing. Treatments 1. 2. & 5 (1, 2 & 3 lbs. 2,4-D) - Damage to weeds appears to be progressively less with lower concentrations. July 28 (26 days following sprays) General observations on the effeot of the sprays on broad-leaved weeds and grasses were recorded numerically as shown i n table 7. Effeot on Strawberry Plants Extracts of notes taken on the effect of the various treatments on the strawberry plants follows: July 4 (2 days following sprays) - In a l l plots the strawberry plants are exhibiting curling of leaves, twisting and curling of petioles to some degree (see figure 11). July 8 Treatment 4 (4 lbs. 2,4-D per acre) - Strawberry plants at present appear poorest of lot. - Curling and crisping of leaves. 64. Table 7 - Effect of the Various Treatments upon the Broad-Leaved Weeds and Grasses as at July 28, 1949. TREATMENTS 1 2 3 4 5 (1 l b . & l b . (3 l b . (4 l b . (2 l b . 2, 4-D . 1 2,4-D) 3,4-D) 2,4-D) 2,4-D) -40 l b . IPC) B B G B G B G B G BLOCK I 2 1.5 4 2 4.5 2 5 1 5 2 II 3 2 4 1 3 2 5 3 5 2 III 3 1 4 2 5 3 5 3 4 2 Sum. 8 4.5 12 5 12.5 7 15 7 14 6 Legend: B — Broad-leaved weeds. G — Grass Rating — I s n i l control 5 = complete control 65. Condition of Strawberry Plants: Leaf counts were made on ten plants per plot making 30 plants per treatment. Plants were selected from the same position i n each plot. The results obtained were of no value since the variations within plots was great also the leaf count gave no indication as to the size of leaf. For example, many plants were found to have a large number of leaves but in many cases the leaves were small.,; while other plants had fewer leaves, but very frequently these leaves were larger. Other methods were tried such as the spread of the plant, height of plant, production of runners, etc., but a l l were found unsatisfactory since none of these methods or combina- tions of these methods gave a complete picture of the true condition of the plants. Thus i t was decided that the best measure of the condition of the strawberry plants was to rate the plants from observation. The writer obtained the cooperation of the Horticulturist and the Head Gardener of the Dominion Experimental Farm, Agassiz, B.C., in rating the plants. Both gentlemen rated the plants independently and the results obtained are summarized i n table 8. Weed Control: General observations were again made on October 30, 1949 on the effect of the treatments on weeds and as before a numerical rating for each treatment was recorded as shown in table 9̂  The weeds at this time were mainly grasses such as oats, millet, Kentucky blue, and couch grass. 66 Figure 10 - Showing a General View of the Layout of Experiment V and the Method of Spraying with a Knapsack Sprayer. 67 I Figure 11 - Showing the Effects of 2,4-D upon the Leaves and Petioles of B r i t i s h Sovereign Strawberry- Plants. The centre l e a f shows the "burning" or " c r i s p i n g " effect caused by 4 l b s . and over of 2,4-D per acre. 68. Table 8 - The condition of the Strawberry Plants as at September 1, 1949. TREATMENTS . 1. 2. 3. 4. 5. (1 l b . (2 l b . (3 l b . (4 l b . (2 l b . 2,4-D 2,4-D) 2,4-D) 2,4-D) 2,4-D) • 4G l b . IPC A B A B A B i A B A B BLOCK 1 4 4 4 4 3 2 3 3 2# 3# II 5 4 4 + 3 3 3 3 3" 4 + 4 III 5 4* 4 3 3 3* 2 2 4 4 Sum. 14 12* 12 + 10 9 8 + 8 8" 1 0 + 11 Legend; Rating: 1 to 5 (poorest to best condition) (hand-weeded plots = 5) A. By Head Gardener. B. By Horticulturist. #Difficult to assess condition of plants in this plot since many of the plants appeared to be damaged by other than sprays (care- lessness of a laborer). 69. Table 9 - Effect of the Various Treatments upon the Weeds as at October 30, 1949. TREATMENTS 1. 8. 3. 4. 5. 6. - (1 l b . 2,4-D) (8 l b . 8,4-D) (3 l b . 8.4-D) (4 lb. 8,4-D) (5 lb.8,4-D +40 lb.IPC) (Check) BLOCK I 8 3 3 8 4 5 II 1 1~ 8 4 5 4 III 1 1 3 3" 5 5 Sum. 4 5" 8 9" 14 14 Legend; Rating: 1 to 5 (poor to good oontrol) 70 DISCUSSION This experiment was designed to study the effect of various concentrations of 2,4-D and 2,4-D supplemented with IPC on both weeds and British Sovereign strawberry plants under f i e l d conditions. The treatments used in this experi- ment were determined in part from the results of the four preceding experiments. Weed Control: From the results i t is noted that curling of leaves was apparent on the broad-leaved weeds within an hour after spraying even in those plots sprayed with 1 pound per acre. Within two days a l l the broad-leaved weeds present were showing typical 2,4-D injury such as curling of the leaves, twisting and curling of the petioles. Harvey and Robbins (11) state that the f i r s t notice- able effect of 2,4-D i s in the stems and leaves which become twisted and bent, with the leaves showing varying epinastic conditions. The stems and leaves may remain green for several weeks after treatment before dying, or they may recover i f the treatment was li g h t . Carlson (4) reporting on the control of weeds in strawberry plantings by the use of 2,4-D states that many weeds showed deformative effects at the low concentra- tions of 400 and 800 parts per million and yellow dock, dandelion and f i e l d violets were k i l l e d . Canada t h i s t l e 71. was injured severely at these concentrations but slowly recovered. Alsike clover was not severely affected at the low concentrations (400 to 800 parts per million), but was k i l l e d at 2,000 to 2,400 parts per million. According to Warren and Hernandez (20) 2,4-D at the rates of 2, 3 and 4 pounds of the acid equivalent per acre gave generally good control of pigweed, lambsquarters, purslane, shepherds-purse, witchgrass and fo x t a i l for a period of 4 to 6 weeks, but annual smartweeds were only slightly affected. The weed Committee of the B.C. Agronomists' Association (22) states that weed species vary considerably i n their reaction to 2,4-D, ranging from very susceptible to highly resistant. Furthermore the stage of growth i s an important factor. A species of weed may be highly susceptible at one stage while at a later stage i t may become quite resistant. Soil and climatic conditions also give marked differences in the effect of 2,4-D on weeds. Most annual weeds, other than those belonging to the grass family, are generally susceptible at the young succulent stage of growth, while many become quite resistant at the flowering or seed stage. Perennial weeds show greater variation in susceptibility to 2,4-D than do annual weeds. In general, the perennial weeds require somewhat higher rates of application of 2,4-D than do the annuals. Susceptible perennial weeds respond more readily to the action of 2,4-D from bud stage to flower stage rather than at earlier stages of growth. 72. Six days after treatment the weeds i n the plots sprayed with a mixture of 2,4-D and IPC were showing the greatest injury with many weeds practically dead. Even the weeds sprayed with 4 pounds of 2,4-D were not showing as much injury. This would appear to he further evidence of the supplementing value of these chemicals for one another as mentioned in the preceding experiment. An examination of table 7 shows that the control of the broad-leaved weeds increased with increase in the concen- tration of 2,4-D u n t i l at 4 pounds per acre the broad-leaved weed control i s 100 per cent. However, i t w i l l be noted that this improvement in weed control i s not in proportion to the increase in amount of 2,4-D applied. These results are i n agreement with those obtained by Warren and Hernandez (20) in weed control i n certain vegetable crops with s o i l applications of 2,4-D. Of particular interest i s treatment 5 (2 lbs. 2,4-D plus 40 lbs. IPC) which shows a broad-leaved weed control of 93.9 per cent. Again, further evidence of supplementing value of these chemicals. The control of grass at this time was not too encouraging as can be seen from table 7. Control of grass improved with increase in 2,4-D but as with the broad-leaved weeds this improvement i s not in proportion to the increase in amount of 2,4-D applied. It w i l l be noted that 2 and 3 pounds of 2,4-D gave the same result. The plots sprayed with the mixture of 2 pounds of 2,4-D and 40 pounds IPC showed a 73. slight improvement in grass control over plots treated with 2 pounds of 2,4-D alone, but the improvement was slightly less than that obtained by use of 3 and 4 pounds of 2,4-D alone. However, since much of the grass present i n the plots at this time was annual hog millet, such results are as expected in view of the results obtained with this grass i n Experiment IV. This provides further evidence of the high degree of resistance of annual hog millet to IPC i n comparison with the other grasses present. Now an examination of table 9, on the effect of the various treatments upon the weeds as at October 30, two months following the second application of treatments, shows that weed control improved with increase i n the concentra- tion of 2,4-D. The plots treated with 2 pounds of 2,4-D plus 40 pounds of IPC show extremely good control of the weeds. It i s also noted that the weeds present i n the plots • at this time were mainly grasses. The broad-leaved weeds were practically extinct. Treatment 5 made a much better showing this time; possibly because the broad-leaved weeds and grasses were much more immature at the time of the second spraying than the weeds were for the f i r s t spraying. It must be remembered that the plots were cleaned up and weeds raked off after complete results were recorded on the f i r s t spraying. According to Freed (9) IPC acts principally as a mitotic poison (prevention of c e l l division), which means i t i s most effective during early growth. Another 74. explanation for the disappointing results obtained from the f i r s t spraying is the pos s i b i l i t y that the IPC was inactivated by the excess moisture in the s o i l at the time of spraying. As mentioned earlier, there had been considerable rainy weather before the f i r s t sprays were applied. According to Mitchell and Marth (16) IPC i s inactivated in the presence of moist, f e r t i l e s o i l as i s the case with 2,4-D. The Effect on Strawberry Plants: Two days following application of the sprays typical 2,4-D injury was noted on the strawberry plants in a l l treated plots. This injury was the same as described previously for the broad-leaved weeds; namely, curling of leaves and twisting and curling of the petioles. Four days later the plants sprayed with 4 pounds of 2,4-D showed a much more extreme 2,4-D injury. The leaves had extreme curling and were becoming crisp. Carlson (4) having sprayed Premier strawberries with 1000 parts per million of 2,4-D reported that about two weeks after application of 2,4-D the strawberry plants in the second-year planting took on a darker green colour, and younger actively growing leaves showed twisting of the petioles. The larger plants showed no deformative effect. The spring planting which was producing runners showed similar responses. There was some indication of curling of the young tender shoots but this was of short duration. 75. In the same paper Carlson reports on another experiment in which he used various concentrations of 2,4-D after harvest and found that the low concentrations 400 and 800 parts per million had no effect on the strawberry plants. Concentra- tions of 1200, 1600 and 2000 parts per million resulted i n slight to moderate twisting of the strawberry petioles, and at 2400 parts per million the petioles were badly twisted. The deformative effects caused by the higher concentrations soon disappeared from the strawberry plants and after 4 to 5 weeks they appeared normal. He further states that when flowers of the everbearing varieties were hit with the spray small and misshapen fr u i t s were produced. Many methods were tried in an attempt to find an accurate estimation of the condition of the strawberry plants. But as pointed out i n the results such measurements as leaf counts, spread of plant, production of runners, etc., either singly or i n combination l e f t much to be desired. Observa- tion ratings appeared to be the best method of recording the condition of the strawberry plants. These ratings are summarized in table 8 and an examination of this table shows that i n a l l treated plots the strawberry plants were less vigorous than i n the hand-weeded plots. The vigour decreased as the concentration of 2,4-D was increased. As expected from previous experiments, the IPC apparently did not affect the strawberry plants to any appreciable degree. It would appear from these results that three or four pounds of 2,4-D 76. per acre i s too much for British Sovereign strawberry plants. This injurious effect was much less with the lower concentra- tions of 2,4-D. It must be appreciated that this loss i n vigour i s not necessarily due entirely to the 2,4-D, but i n part, at least, some loss would be due to competition with weeds. For i t must be remembered that due to rainy weather the weeds were allowed to become t a l l and dense before sprays were applied. Further these herbicides required considerable time to affect the more mature annual weeds. During this time the weeds were s t i l l competing with the strawberry plants While, on the other hand, i n the hand-weeded plots the weeds were removed immediately. Thus, the importance of applying the herbicides when the weeds are small and succulent. CONCLUSIONS Six treatments (2,4-D and 2,4-D plus IPC) were l a i d out in three replicates on a maiden British Sovereign straw- berry plantation, and 1, 2, 3 and 4 pounds of 2,4-D per acre and 2 pounds of 2,4-D plus 40 pounds of IPC per acre were the spray treatments compared with a hand-weeded check. It was found that up to 2 pounds of 2,4-D per acre did not . seriously damage strawberry plants and gave satisfactory control of both broad-leaved weeds and grasses. A l l plots treated with herbicides resulted in slightly less vigorous strawberry plants than the hand-weeded check. It was 77. explained that this decrease i n vigour was a result, in part, at least, of allowing the weeds to become t a l l and very dense before applying the sprays (unavoidable i n this experiment due to weather conditions). Thus these weeds oompeted with the strawberry plants for a considerable time after sprays were applied while i n the hand-weeded plots the weeds were removed Immediately. It is appreciated that 2 pounds of 2,4-D and 40 pounds of IPC per adre w i l l not be required for weed control i n a l l strawberry plantations. The amounts to be used w i l l depend upon the age and species of weeds present. In t h i s experiment i t w i l l be remembered that 60 - 65% of the total weed population consisted of Lady's thumb (Polygonum Persicaria L.) which is very resistant to 2,4-D. Also wild millet (Echinochloa crusgalll L. Beaux) made up 10% of the t o t a l weed population and this grass shows considerable resistance to IPC. In addition i t must be pointed out that there are many new formulations of IPC coming on the market which are effective at much lower con- centrations than the formulation used in t h i s experiment. Of the herbioides available to-day there appears to be no glose r i v a l for the mixture of 2,4-D and IPC as a seleotive herbicide for strawberries. Under conditions of this experiment a mixture of up to 2 pounds of 2,4-D plus 40 pounds of IPC can be safely recommended for the deweeding of British Sovereign straw- berry plantations, provided i t i s not used when the plants are in blossom. 7 8 . S U M M A R Y Information on the use of herbicides for weed control i n strawberries i s limited, but grower interest has increased to the point where recommendations for safe usage are needed. It has been shown that strawberry varietal responses to 2,4-D are wide and therefore i t is necessary to determine the concentration of 2,4-D suitable for each variety. Some newer herbicides, toxic to grasses, have recently been introduced which might have a place either alone or i n a mixture with 2,4-D i n a weed control program for strawberries. With these two points in mind the following -experiments were conducted on British Sovereign strawberry plants and various grasses at the Dominion Experimental Farm, Agassiz i n 1949. Five experiments in a l l were carried out with the object of studying the use of selective herbicides on strawberries. Before laying out a.large,replicated experi- ment i t was f e l t that (a) the general response of strawberry plants to various herbicides and (b) the effect of these herbicides on both broad-leaved weeds and grasses should be determined. Small plots were l a i d out on a three year old strawberry plantation and subjected to 34 different treat- ments (Experiment I ) . Similar treatments were applied i n Experiments II and III to newly seeded and established grasses These treatments consisted of different concentrations and mixtures of the following: 79. 2,4-dichlorophenoxyacetic acid (2,4-D) Sodium salt of trichloroacetic acid (TCA) Ammonium salt of Isopropyl N-phenyl carbamate (IPC) 2 methyl-4-chlorophenoxyacetic acid (MCP) Sodium pentaohlorophenate (PCP) Ammonium salt of dinitro-O-secondary butyl phenol (DNOSBP/ Potassium cyanate Emulsifiable pentaehlorophenol Effect on Strawberry Plants IPC at 5 to 80 pounds per acre had no effect on established strawberry plants. 2,4-D at 150 gallons per acre of 1000 ppm, either alone or with IPC, l e f t the plants normal after 2 months although there was slight curvature of petioles produced after 3 weeks. A l l other treatments either k i l l e d the strawberry plants or l e f t them in a very weakened condition. A mixture of 2,4-D and IPC appeared promising. Effect on Grasses As reported by other workers, a l l herbicides but 2,4-D controlled grasses while 2,4-D controlled the broad- leaved weeds. IPC at 80 pounds per acre in a spray alone and with 2,4-D controlled or seriously stunted the grass species present. It took 4 weeks to become completely effective. Applied as a dust, 40 pounds per acre gave complete k i l l of seedling grass mixture. 80. Experiment IV was laid out in the greenhouse with mixtures of three levels of 2,4-D and five levels of IPC on four species of grass. This experiment has shown that 2 pounds of 2,4-D and 40 pounds of IPC gives very satisfactory control of perennial rye grass, creeping red fescue, and orchard grass ( a l l perennial grasses), hut not of the annual hog millet. Millet, fortunately, i s rarely found as a weed, but was present in the plots of the experiment to follow. In the f i n a l experiment six treatments (2,4-D and 2,4-D plus IPC) were l a i d out in three replicates on a maiden British Sovereign strawberry plantation. Treatments of 1, 2, 3 and 4 pounds of 2,4-D per acre and 2 pounds of 2,4-D plus 40 pounds of IPC per acre were compared with a hand-weeded check. It was found that up to 2 pounds of 2,4-D per acre did not seriously damage strawberry plants and gave satisfactory control of the broad-leaved weeds. A mixture of 2 pounds of 2,4-D and 40 pounds of IPC per acre gave satisfactory control of both broad-leaved weeds and grasses. A l l plots treated with herbicides resulted in slightly less vigorous strawberry plants than the hand- weeded check. It was explained that this decrease in vigour was a result, in part, at least, of allowing the weeds to become t a l l and very dense before applying sprays (unavoidable i n this experiment due to weather conditions). Thus, these weeds competed with the strawberry plants for a considerable time after sprays were applied D4iile in the 81. hand-weeded plots the weeds were removed immediately. In general, the conclusions from these experiments are: (1) that the sprays should i f possible be applied when the weeds are small and succulent, especially i s this true for annuals; (2) under conditions of this experiment a mixture of up to 2 pounds of 2,4-D plus 40 pounds of IPC can be safely recommended for the deweeding of British Sovereign strawberry plantations provided i t i s not used when the plants are in blossom. LITERATURE CITED 83. 1. Barrons, K.C., TCA ... A promising new chemical for grass control. Down to Earth, Dow Chemical Comp- any, Midland, Michigan, Vol.4, No.4, Spring, 1949, pp 8-9. 2. Bush R., Tar-Oil weed k i l l e r for strawberry beds. Grower, 1948, 30:613. 3. Carder, A.C, Control of dandelions in strawberries by 2.4-D. F i f t h Annual North Central Weed Control Conference Research Report, Springfield, I l l i n o i s , 1948. 4. Carlson,R.F., Control of weeds i n strawberry plantings by the use of 2.4-dichlorophenoz:yacetic aoid. Proc. Amer. Soc. Hort. Sci., W.E. Humphrey Press Inc., Geneva, N.T., 1947, 49:221-3. 5. Carlson, R.F. and Moulton, J.E., Use of the ammonium salt of triohloroacetate. the sodium salt of trlchloroacetate. ammonium thiocyanate. and herbicide "PBW. in the eradication of grasses. and the effect of these chemicals on strawberry and raspberry plants. The Quarterly Bulletin, Michigan State College, East Lansing, 1948, 38:413-21. 83. 6., Davidson, J.H., Weed control in an established straw- berry (Variety Premier) planting with 2.4-dioh- lorophenoxvacetic acid. F i f t h Annual North Central Weed Control Conference Research Report, Spring- f i e l d , I l l i n o i s , 1948. 7. Doxey, D., The effeot of Isopropvl N-phenol carbamate on mitosis in rye (Secale cereale) and onion (Allium cepa). Annals of Botany, New Series, vol. 13, No.51, July 1949, pp. 329-334. 8. Elder, W.C., Elwell, H.M., and Romshe, F.A., Chemical Control of weeds and brush in Oklahoma, Oklahoma Agricultural Experiment Station, Oklahoma A. & M. College, Stillwater, Bulletin B-335, June, 1949. 9. Freed, V., Letter to the writer, from Paul Logue, Phosphate Division, Monsanto Limited, St. Louis, July 7, 1949. 10. Hance, F.E., Recent developments in weed onntrol in sugar cane, Science, Washington, D.C., 1948, 108:278-9. 11. Harvey, and Robbins, 2.4-D as a weed k i l l e r . College Agriculture, University of California, Berkeley, Circular 133, June, 1947. 84. 12. Hitchcock, A.E., and Zimmerman, P.W., Activation of 2.4-D by various adjuvants. Boyce Thompson Institute, 1948, 15:173-93. 13. Klein, L.G., Strawberries and 2.4-D. Canadian Grower, 1947, 70:7: 8-16. 14. Lachman, W.H., Some studies using isopropyl N-phenyl carbamate as a selective herbicide. Prooi Amer. Hort. Sci., W.E. Humphrey Press Inc., Geneva, N.Y., 1948, 51:541-4. 15. Mitchell, J.W. and Marth, P.C., Effects of 2.4-dioh- lorophenoxyacetic acid on the growth of grass plants. Botanical Gazette, 1945, vol.107, No.2, pp. 282-84. 16. Mitchell, J.W. and Marth, P.C., Sensitivity of grasses and some crop plants to isopropyl N-phenyl carbamate. Science, Washington, D.C, 1947, 106:15-7. 17. Nylund, R.E., A study on the use of 2.4-D for weed control in strawberries. F i f t h Annual North Central Weed Control Conference Research Report, Springfield, I l l i n o i s , 1948. 18. Otis, C.E., Strawberry weed control in the Pacific Northwest. Down to Earth, The Dow Chemical 85. Company, Midland, Michigan, 1947, vol.3, No.3, p.16. 19. S l i f e , F.W. and Ball, H.L., A preliminary report on spray*strawberries with 2.4-D and TCA, F i f t h Annual North Central Weed Control Conference Research Report, Springfield, I l l i n o i s , 1948. 20. Warren, G.F., and Hernandez, T.P., Weed control i n certain vegetable crops with s o i l applications of 2.4-D. Proc. Amer. Soc. Hort. Soi., W.F. Humphrey Press Inc., Geneva, N.Y. 1948, 51:515-25. 21. , Investigations of weed control methods in horticulture and truck crops. F i f t h Annual North Central Weed Control Conference Research Report, Springfield, I l l i n o i s , 1948. 22. , Recommendations on the use of 2.4-D, Weed Committee of the B.C. Agronomists' Association, Victoria, British Columbia Department of Agriculture, Field Crop Stencil No.l, 1948. 23. , Report of ac t i v i t i e s of the Division of Horticulture for the months of A p r i l . May and June. 1948, Dominion Experimental Farm Service, Ottawa, 1948. 86. APPENDIX Following are complete s t a t i s t i c a l analyses of the effect of applications of various amounts of 2,4-D and mixtures of 2,4-D and IPC on the height of hog millet (Panicum miliaceum) as at September 11, 1949, and of the effect of applications of various amounts of 2,4-D and mixtures of 2,4-D and IPC on the weight of clippings from the various grasses, as shown, as at September 30, 1949. Data obtained from Experiment IV. 87. Effect of Applications of Various Amounts of 2,4-D and Mixtures of 2,4-D and IPC on the Height of Hog Millet (Panicum miliaceum) as at September 11, 1949. Block Treatment Treatments I II III Sum. : Mean 1 13 10 14 37 12.3 2 11 13 14 38 12.7 3 9 10 15 34 11.3 4 8 12 12 32 10.7 5 8 12 10 30 10.0 6 8 8 9 25 8.3 7 11 14 9 34 11.3 8 12 12 11 35 11.7 9 8 11 12 31 10.3 10 7 9 11 27 9.0 11 8 8 8 24 8.0 12 6 9 6 23 7.7 13 8 10 9 27 9.0 14 9 11 15 35 11.7 16 9 9 7 25 8.3 16 10 7 6 23 7.7 17 5 7 10 22 7.3 18 6 6 5 17 5.7 19 0 1 0 1 0.3 20 0 4 1 5 1.7 21 2 4 3 9 3.0 22 4 4 3 11 3.7 23 14 14 15 43 14.3 Blk.Totals 178 215 205 Blk.Mean 7.7 9.3 8.9 Grand Total 598 General Mean 8.7 88 ANALYSIS OF VARIANCE Table Source of Degrees of Sum of Variance Variance value F Variation Freedom Squares ratio in F. at P = .05 Total 68 Treatment 22 Blocks 2 847 662 32 30.1 16.0 8.60 4.57 1.81 3.21 Error 44 153 3.5 M.S.D. for Treatments at .05 level = 1.08 89. Effect of Applications of Various Amounts of 2,4-D and Mixtures of 2,4-D and IPC on the weight of Clippings from Creeping Red Fescue (Festuca rubra) as at Sept. 30, 1949. (M.S.D. at .05 level = 0.5) Block - Treatment Treatments I II III Sum. Mean 1 7.0 6.2 17.0 30.2 10.1 2 4.5 2.5 9.0 16.0 5.3 3 1.0 2.5 4.0 7.5 2.5 4 0.5 4.0 2.0 6.5 2.2 5 0.5 0.9 3.0 4.4 1.5 6 1.0 0.5 3.0 4.5 1.5 7 11.5 5 .0 10.0 26.5 8.8 8 1.0 8.0 3.0 12.0 4.0 9 10.0 3.5 4.0 17.5 5.8 10 8.0 1.5 2.0 11.5 3.8 11 4.0 4.0 0.0 8.0 2.7 12 2.0 1.0 2.0 5.0 1.7 13 9.0 5.5 4.0 18.5 6.2 14 8.0 3.0 4.0 15.0 5.0 15 5.5 1.5 4.0 11.0 3.7 16 4.0 1.5 1.0 6.5 2.2 17 2.0 1.5 2.0 5.5 1.8 18 3.5 1.5 o.o 5.0 1.7 19 9.0 6.0 11.0 26.0 8.7 20 3.0 2.3 6.0 11.3 3.8 21 7.0 5.0 12.0 24.0 8.0 22 13.0 6.0 8.0 27.0 9.0 23 11.5 9.0 7.0 27.5 9.2 Blk.Totals 126.5 82.4 118.0 Blk.Mean 5.5 3.6 5.1 Grand Total 326.9 General Mean 4.7 ANALYSIS OTP VARIANCE 90. Table Source of Degrees of Sum of Variance Variance value E Variation Freedom Squares , ratio i n E. at P =.05 Tout 68 914 Treatment 22 528 24 3.12 1.81 Blocks 2 48 24 3.12 3.21 Error 44 338 7 .7 M.S.D. for Treatments = 0.507 at .05 level. 91. Effect of Applications of Various Amounts of 2,4-D and Mixtures of 2,4-D and IPC on the weight of Clippings from Perennial Rye Grass (Lolium perenne) as at Sept. 30, 1949. (1/ [.S.D. at .05 level = 3.7) BlOCk ±11 Treatment Treatments I II Sum. Mean 1 33.0 10.0 37.0 80.0 26.7 2 8.0 8.0 25.0 41.0 13.7 3 1.5 4.0 6.0 11.5 3.8 4 1.0 6.0 7.0 14.0 4.7 5 1.5 3.5 7.0 12.0 4.0 6 1.5 0.5 10.0 12.0 4.0 7 40.0 18.5 22.0 80.5 26.8 8 8.0 12.0 12.0 32.0 10.7 9 23.5 8.5 15.0 47.0 15.7 10 10.5 2.0 10.5 23.0 7.7 11 9.0 3.0 1.0 13.0 4.7 12 5.5 2.5 5.0 13.0 4.3 13 20.0 11.5 15.0 46.5 15.5 14 13.0 10.5 19.0 42.5 14.2 15 19.0 6.5 12.0 37.5 12.5 16 13.0 2.5 1.5 17.0 5.7 17 9.0 2.5 9.0 20.5 6.8 18 7.0 3.5 1.0 11.5 3.8 19 22.5 13.5 50.0 86.0 28.7 20 13.5 13.5 12.0 39.0 13.0 21 7.0 11.2 /17.0 35.2 11.7 22 27.5 14.8 13.0 55.3 18.4 23 18.0 10.0 19.0 47.0 15.7 Blk.Totals 312.5 178.5 326.0 Blk. Mean 13.6 7.8 14.2 Grand Total 817 General Mean 11.9 ANALYSIS OF VARIANCE Table Source of Degrees of Sum of Variance Variance value F Variation Freedom Squares ratio in F. at P =.05 Total 68 6390.33 Treatment 22 Blocks 2 Error 44 3965.21 180.24 578.18 289.09 1846.94 41.98 4.29 6.89 18.1 3.21 [.S.D. for Treatments = 3.7 at .05 level. Effect of Applications of Various Amounts of 2,4-D and Mixtures of 2,4<*D and IPC on the weight of Clippings from Orchard Grass (Dactylis glomerata) as at Sept.30, 1949. (M.S.D. at .05 level = 2.8) I ; • Treatments I Block II III Sum. Treatment Mean 1 20.5 6.0 15.0 41.5 13.8 2 25.0 2.0 10.0 37.0 12.3 3 4.0 4.0 7.0 15.0 5.0 4 1.0 2.5 5.0 8.5 2.8 5 1.0 2.0 2.0 5.0 1.7 6 1.0 1.0 3.0 5.0 1.7 7 16.5 5.0 10.0 31.5 10.5 8 9.0 5.0 5.0 19.0 6.3 9 14.0 4.5 2.0 20.5 6.8 10 5.5 2.0 1.0 8.5 2.8 11 2.0 4.0 1.0 7.0 2.3 12 2.0 2.0 1.0 5.0 1.7 13 11.0 5.0 4.0 20.0 6.7 14 9.5 4.0 6.0 19.5 6.5 15 11.5 3.0 4.0 18.5 6.2 16 4.0 2.0 1.0 7.0 2.3 17 3.5 1.0 2.0 6.5 2.2 18 1.5 2.0 1.0 4.5 1.5 19 4.5 2.5 10.0 17.0 5.7 20 1.5 0.5 3.0 5.0 1.7 21 6.0 7.0 17.0 30.0 10.0 22 38.0 7.0 9.0 54.0 18.0 23 18.0 9.0 11.0 38.0 12.7 Blk.Totals 210.5 83.0 130.0 Blk.Mean 9.15 3.61 5.65 Grand Total ... 423.5 General Mean 6.1 94. ANALYSIS OF VARIANCE Table Source of Degrees of Sum of Variance Variance value F Variation Freedom Squares ration i n F at P =.05 Total Treatment Blocks Error 68 22 2 44 2876.94 1456.11 66.19 361.53 180.77 1059.30 24.08 2.75 7.51 1.81 3.21 I.S.D. for Treatments s 2.8 at .05 level. . . . . 9 5 . Effect of Applications of Various Amounts of 2,4-D and Mixtures of 2,4-D and IPC on the weight of Clippings from Hog Millet (Fanlcum miliaoeum) (M.S.D. at .D5 level = 6.9) Block Treatment Treatments I II III Sum. Mean 1 44..0 16.0 44.0 104.0 34.7 2 42.0 35.0 69.0 146.0 48.7 3 42.0 17.5 72.0 131.5 43.8 4 44.0 29.0 64.0 137.0 45.7 5 45.0 28.0 82.0 155.0 51.7 6 49.0 37.0 80.0 166.0 55.3 7 33.0 42.5 35.0 110.5 36.8 8 50.0 38.0 49.0 137.0 45.7 9 26.0 19.0 57.0 102.0 34.0 10 26.0 34.0 65.0 125.0 41.7 11 33.0 14.5 32.0 79.5 26.5 12 39.0 38.5 41.0 118.5 39.5 13 31.0 20.5 57.0 108.5 36.2 14 24.0 24.0 41.0 89.0 29.7 15 34.5 18.5 34.0 87.0 29.0 16 33.0 25.0 32.0 90.0 30.0 17 20.0 20.0 61.0 101.0 33.7 18 31.5 9.0 30.0 70.5 23.5 19 o.o 4.5 o.o 4.5 1.5 20 1.5 22.0 4.0 27.5 9.2 21 5.5 18.5 1.3 37.0 12.3 22 26.0 10.0 7.0 43.0 14.3 23 49.0 30.5 54.0 133.5 44.5 Blk.Totals 729 551.5 1023.0 Blk. Mean 51.7 23.9 44.5 Grand Total 2303.5 General Mean 33.3 ANALYSIS OF VARIANCE Table Source of Degrees of , Sum of Variance Variance . value F Variation Freedom Squares ration in F. at P • .05 Total 68 24,144.08 Treatment 22 12,931.58 587.8 4.12 1.81 Blocks 2 4,931.23 2465.6 17.26 3.21 Error 44 6,281.27 142.8 M.S.D. for Treatments * 6.9 at .05 lev e l .

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