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Insect and disease risk factors in established interior spruce plantations Cozens, Russel David 1985

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Insect and Disease Risk t-actors In Established Interior Spruce Plantations by Russel David Cozens 8.S.F., The University of British Columbia A Thesis Submitted in Partial Fulfillment of The Requirements for the Degree of Master of Forestry in The Faculty of Graduate Studies (Department of Forestry, Forest Entomology) We accept this thesis as conforming to the required standard The University of British Columbia October 1984 ©Russel David Cozens, 1984 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I agree t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by t h e head o f my department o r by h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . The U n i v e r s i t y o f B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date <Bj> O^.03 DE-6 (3/81) 1 ] ABSTRACT forest insects and diseases active in immature interior spruce stands in the central interior of British Columbia and their possible implications in forest management practices have been surveyed. Collection records, spanning the period 1949 to 1982, from the Forest Insect and Disease Survey of the Canadian Forestry Service were reviewed for the Prince George Timber Supply Area and the pest incidence in immature interior spruce stands summarized. Twenty-two plantations, established between 1963 and 1973, were surveyed to determine the relative incidence of the major insect and pathogen pests of immature spruce in Supply Block 'G' of the Prince George Timber Supply Area. A bud midge, likely Rhabdophaga swainei Felt (Diptera: Cecidomyiidae), and a terminal weevil, Pissodes strobi Peck (Coleoptera: Curculionidae), were found to consistently infest and damage a significant number of immature interior spruce trees. A spruce stand stocking profile was developed as a basis for discussion of management practices in plantations and immature stands. The stocking profile can be used in the determination of not only pest management policy decisions but in stand management decisions affecting stand density and, ultimately, merchantable yield at harvest. The findings confirmed that forest management must be actively practiced throughout the l i f e of a forest stand. To be successful, however, stand management guidelines and merchantable yield projections are required. These guidelines and projections must include the influences of insects and diseases upon the forest crop in their development model. This information is particularly important in the development of complete Timber Supply Area plans and for the flagging of pest hazard periods during the development of spruce forests. i \ TABLE Of CONTENTS Page TITLE PAGE i ABSTRACT i i TABLE Of CONTENTS iv LIST Of TABLES vi LIST Of FIGURES v i i ACKNOWLEDGEMENT v i i i 1. INTRODUCTION 1 1.1 Overview of the Prince George Timber Supply Area A 1.2 Description of Supply Block *G' 10 1.2.1 General Overview 10 1.2.2 Industrial and Silvicultural Development 10 1.2.3 forest Management Strategies 14 1.3 The Spruce Resource 16 1.3.1 Taxonomy 16 1.3.2 Habitat Conditions 17 1.3.3 Life History 19 1.3.4 Growth of Planted Spruce 22 1.4 Study Objectives 24 2. METHODS 27 2.1 Literature and Information Compilations 27 2.1.1 Insect Pests 27 2.1.2 forest Diseases 28 2.2 field Survey of Spruce Plantations 29 3. RESULTS 36 3.1 Literature and Information Compilations " 36 3.1.1 Insect Pests 36 3.1.2 Forest Diseases 40 3.2 Field Survey of Spruce Plantations 47 4. DISCUSSIUN 34 5. CONCLUSIONS 66 6. RECOMMENDATIONS 67 REFERENCES 69 APPENDIX I Spruce Plantation Pest Field Survey Recording 73 Form APPENDIX II Spruce Plantation Pest Summary Form 75 APPENDIX III Sample Aerial Photograph (1:20 000 scale) 77 v i LIST OF TABLES Table Page I forest plantations containing significant proportions 7 of spruce by forest District for the Prince George Timber Supply Area. II Short-term (20 year) net merchantable timber supply 25 by species and Supply Block in the Prince George Timber Supply Area. I l l Spruce plantation listing for Supply Block 'G' in the 30 Prince George Timber Supply Area for plantations established in 1973 or earlier. IV Insect pests of immature spruces that may occur in 37 central British Columbia. V Insect pests of immature spruces recorded in forest 41 Insect and Disease Survey records for the Prince George Timber Supply Area. VI forest diseases of immature spruces that may occur in 45 central British Columbia. VII forest diseases of immature spruces recorded in the forest 48 Insect and Disease Survey records for the Prince George Timber Supply Area. VIII Summary of descriptive statistics for immature stands 50 surveyed for pest occurrence and incidence in Supply Block 'G' of the Prince George Timber Supply Area. IX Summary of recordings of pests and other tree 52 damaging agents in plantation surveys. v i i LIST OF FIGURES Figure Page A hypothetical representation of the relative risk 2 of a planted spruce (Picea spp.) forest in the Prince George Timber Supply Area not reaching merchantability or being available for an economic harvest as a result of chronic growth and volume reduction, a sudden and catastrophic stand mortality, or a combination of both. The Prince George Timber Supply Area showing Supply 5 Blocks and Forest Districts. Supply Block 'G' of the Prince George Timber Supply 11 Area showing ecological classification units. Location of spruce plantations established in 1973 35 or earlier in Supply Block 'G' of the Prince George Timber Supply Area. General areas of activity of major pests of immature 39 interior spruce trees. Occurrence of Pissodes strobi and bud midge attack 53 on immature interior spruce in stands examined in Supply Block 'G' of the Prince George Timber Supply Area. 7 Projected performance of interior spruce on Aralia 59 sites in the central interior of British Columbia. 8 Number of healthy planted interior spruce trees per 61 hectare by stand age for stands surveyed in Supply Block 'G' of the Prince George Timber Supply Area compared to projected performance on Aralia sites in the central interior of British Columbia. 9 Routine stand survey and monitoring entries necessary in the development of a merchantable interior spruce forest. 65 ACKNOWLEDGEMENT I wish to acknowledge the support, suggestions and constructive criticism provided by my supervisor, Dr. John McLean, the members of my graduate committee, Dr. Bart van der Kamp and Dr. Bob DeBoo, and Dr. John Bassman. Dr. Allan Van Sickle, David Evans and Dr. John Hopkins, of the Forest Insect and Disease Survey, were extremely helpful in the compilation of historical pest data. I thank the British Columbia Forest Service, Prince George Forest Region, for providing the opportunity and support for me to pursue this programme of study. 1 Insect and Disease Risk ractors In Established Interior Spruce Plantations 1. INTRODUCTION Thirty-nine percent of the mature volume of the Prince George Timber Supply Area (T.S.A.) is spruce (Picea spp.) (Anon. 1979). Fifty-five percent of the annual volume harvested is comprised of spruce'''. After the harvest of mature spruce forests, the sites are usually treated by various silvicultural methods to assist in the establishment of a new spruce forest. Natural regeneration of spruce on the sites of the central interior of British Columbia has proved to be generally unsuccessful within necessary time frames, so plantation forestry is practiced extensively. There are currently vast areas of spruce plantations in the Prince George T.S.A. The risk of a forest not reaching merchantability, or not being available for an economic harvest by a particular time, varies throughout the rotation (Fig. 1). This risk may manifest itself in one, or both, of two ways: 1- chronic growth and volume reduction over most of the l i f e of a stand, such as would occur as a result of root rot H. Willis. Planning Officer. B.C. Forest Service, Prince George Forest Region. Prince George, B.C. personal communication. O 3 50 75 lob ~I25 ISo STAND AGE (years) F i g u r e 1- A h y p o t h e t i c a l r e p r e s e n t a t i o n o f the r e l a t i v e r i s k o f a p l a n t e d spruce ( P i c e a spp.) f o r e s t i n the P r i n c e George Timber Supply Area not r e a c h i n g m e r c h a n t a b i l i t y o r being a v a i l a b l e f o r an economic h a r v e s t as a r e s u l t o f c h r o n i c growth and volume r e d u c t i o n , a sudden and c a t a s t r o p h i c stand m o r t a l i t y , o r a combination o f b o t h . 3 infestation; and, 2- a sudden and catastrophic mortality of the stand, such as would result from fire or a defoliator outbreak in an immature stand or a bark beetle epidemic in mature forests. Initially, a high risk is associated with plantation establishment and development to the 1free-to-grow1 stage. Many factors may be active at this time; primarily cutworms, brush invasion and the effects of planting upon the seedlings. Risk then usually decreases and is associated with those agents causing mortality and, to a greater extent, those causing tree deformation and growth losses which ultimately reduce merchantability. These factors are often overlooked since trees s t i l l occupy the site — even i f they may never contribute to the merchantability of the stand. As the stand reaches merchantability the risk factors increase and are associated with catastrophic mortality; primarily caused by bark beetles and windthrow, often associated with root rot in the mature and overmature forests. This is an expected phenomenon associated with the natural succession of the spruce forest. Merchantability of a spruce stand is largely determined in its early years — between the 1free-to-grow1 stage, which is reached about ten years after plantation establishment throughout most of the Prince George T.S.A., and an approximate age of 35 years, when a thinning operation may be conducted. The activity of pest agents in the immature spruce stands during this 25-year span may preclude crop enhancement through thinning and ultimately reduce stand merchantability. The importance of these pest agents will be addressed in the context of overall Timber Supply Area forest management objectives. 4 1.1 Overview of the Prince George Timber Supply Area The Prince George T.S.A. contains approximately 7 773 000 hectares consisting of 5 941 470 hectares of productive forest land and 1 791 530 hectares of non-productive forest land (Anon. 1982). It encompasses, either totally or partially, 16 Public Sustained Yield Units, two Tree Farm Licences, two Special Sales Areas and the Sustut Block, formerly part of Tree Farm Licence No. 1 (Fig. 2). The Timber Supply Area is sub-divided into nine Supply Blocks, each forming a supply unit to existing manufacturing centres. Supply Blocks provide flexibility in allocating the T.S.A. allowable annual cut to various licensees in different parts of the T.S.A. and in altering that allocation from one time period to another as may be required. There are four Forest Districts within the T.S.A., with offices in Fort St. James, Vanderhoof and Prince George (two). The annual allowable cut for the Prince George T.S.A. was set at 8 700 000 cubic metres (m"5) by the Chief Forester for the i n i t i a l five-year period commencing 1 January 1981 (Anon. 1982). One of the major factors related to the maintenance of this rate of harvest must be to ensure that species volume harvested equate with species volumes of the forest inventory. The present mature volume breakdown in the T.S.A. is: 39% spruce, 35% lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.), 19% subalpine f i r (Abies lasiocarpa (Hook.)Nutt.) and 7% comprised of other species. The current harvest for the T.S.A. is : 55% spruce, 31% lodgepole pine, 12% subalpine f i r and 2% comprised 5 FOREST DISTRICT BOUNDARY B SUPPLY BLOCK Figure 2- The Prince George Timber Supply Area showing Supply Blocks and Forest D i s t r i c t s . 6 of other species . The eastern portion of the T.S.A., specifically Supply Blocks E, G and H, contributes heavily to the spruce component harvested, as over one-half of its merchantable volume is comprised of this species. As the present mature spruce and spruce-mixture stands are harvested, in almost every instance, spruce plantations will be established in their place. The result will be vast areas of relatively even-aged immature spruce forests. There are currently 106 532 hectares of spruce and spruce-mixture plantations in the Prince George T.S.A. (Table I) (Anon. 1984a) which have been established since 1963. These plantations must produce merchantable timber to the industry within 85 to 100 years after 2 establishment, as the rotation age indicates for each particular area . It should be clear that both the Forest Service and forest companies, while possibly not being fully aware of the fact, are already dependent upon immature spruce forests to ensure maintenance of an annual allowable rate of harvest to maintain a viable forest-based economy for the future. The investment in these immature forests necessitates their management and protection. While, in many instances, general practices have been established, each situation will require specific pest management prescriptions, taking into consideration significant local conditions. H. Willis. Planning Officer. B.C. Forest Service, Prince George Forest Region. Prince George, B.C. personal communication. R.J. Barrett. T.S.A. Planning Forester. B.C. Forest Service, Prince George Forest Region. Prince George, B.C. personal communication. Table I - Forest plantations containing significant proportions of spruce by Forest D i s t r i c t for the Prince George Timber Supply Area. Data compiled from Site History Record Summaries (Anon. 1984a). Forest Di s t r i c t Area of Plantations (Ha) by Year of Establishment Totals (Ha) before 1968 1968-1972 1973-1977 1978-1982 1983 Prince George West 35 514 6137 11321 2892 20899 Prince George East 1064 5065 23449 34684 8902 73164 Vanderhoof 0 0 1399 2442 517 4358 F t . St. James 0 291 3233 3183 1404 8111 Totals for Prince George Timber Supply Area 1099 5870 34218 51630 13715 106532 8 The primary objective of Timber Supply Area management planning is to supply raw material of specific dimensions and shapes to the conversion plants'*". This can be interpreted to mean that timber must be supplied to maintain the sawmills, plywood mills and pulp mills within the T.S.A. To accomplish this, uniform logs free of crooks, forks and other defects must be supplied at a realistic cost to remain competitive in world markets. Guidelines for the management of immature stands must be such that a clear butt log of at least ten metres can be obtained. The management strategies of some Licensees may differ from the primary objectives, but are s t i l l quite specific in their intent. In anticipation of a fibre-oriented economy some are anxious to pursue forest management that will produce the greatest amount of wood fibre 2 over the shortest rotation in the most economical manner . This maximization of fibre production would not preclude sawn lumber or veneer production but may result in changes in the conversion processes to adapt equipment and procedures to be compatible with the raw material. Regardless of the chosen path of forest management, both the economic livelihood of the forest industry and the stability of many communities are dependent upon maximization of wood production from every hectare of commercial forest land and a continuous supply of timber from those forest lands. 1 R.J. Barrett. T.S.A. Planning i-orester. B.C. Forest Service, Prince George Forest Region. Prince George, B.C. personal communication. 2 M.S. Litchfield. Planning Supervisor. Northwood Pulp and Timber Ltd. Prince George, B.C. personal communication. (Present position and address: Supervisor, Forest Development and Planning. Fraser Incorporated. Edmundston, New Brunswick). 9 This is where a potential problem lies. The conditions that are created by efforts to maintain the forest industry are sometimes ideal for the maintenance of serious pests of the immature forest. Such a potential situation is not unique to the Prince George T.S.A. or to British Columbia. Sterner and Davidson (1983) described several serious pest occurrences in forests regenerated after harvesting. In the Maritime provinces, the spruce bud moth (Zeiraphera  canadensis Mut. & Free. (Lepidoptera: Olethreutidae)) had affected as many as 15% of white spruce (Picea glauca (Moench) Voss) in a l l but one plantation examined in 1982. A total of 11 000 hectares of white spruce plantations in New Brunswick was sprayed with fenitrothion in that year in an attempt to control the bud moth. Spruce budworm (Chorisoneura  fumiferana (Clem.) (Lepidoptera: Tortricidae)) occurred in a l l white spruce plantations examined in the Maritimes, with as many as 25% of the new shoots being affected. The white pine weevil so adversely affects eastern white pine (Pissodes strobi L.) and Norway spruce (Picea abies (L.) Karst.) that these two species are no longer planted in high hazard areas of eastern Canada and the United States. High populations of white pine weevil continue to exist throughout Quebec and Ontario in pine (Pinus spp.) and spruce (Picea spp.) plantations. Surveys have shown as many as 85% of Sitka spruce (Picea sitchensis (Bong.) Carr.) leaders attacked in plantations examined in the Vancouver Forest Region, where the planting of Sitka spruce has been severely curtailed in many locations on Vancouver Island because of this insect''". P.M. Wood. Pest Management Coordinator. B.C. Forest Service, Vancouver Forest Region. Burnaby, B.C. personal communication. 10 1.2 Description of Supply Block 'G' 1.2.1 General Overview Supply Block 'G' of the Prince George T.S.A. is located to the southeast of Prince George; east of the Fraser River and predominantly south of Highway 16E. It includes minor tributaries of the Fraser River on its western side, the major part of the Willow River drainage and a substantial portion of the Bowron River drainage. This Supply Block is totally within the Prince George East Forest District. Ecological classification of Supply Block 'G' (Fig. 3) shows that a l l areas above 1250 metres (m) above sea level are in the Engelmann Spruce-Subalpine Fir association (ESSFh). The portion of the Supply Block below 1250 m in elevation, where most of the best spruce growing sites exist, was included in the Sub-Boreal Spruce association (SBSc, SBSe, or SBSj)1. 1.2.2 Industrial and Silvicultural Development The Prince George area has supported an active forest industry since the early 1900's with spruce generally being the preferred species of harvest. In 1908, the construction of the Grand Trunk Pacific A. McLeod and C. Delong. Regional Pedologist and Ecologist, respectively. B.C. Forest Service, Prince George Forest Region. Prince George, B.C. personal communication. 11 Prince George F i g u r e 3- Supply B l o c k 'G' o f the P r i n c e George Timber Supply Area showing e c o l o g i c a l c l a s s i f i c a t i o n u n i t s . 12 Railway through Fort George sparked a boom based on tie-cutting, sawmilling and land speculation. Logging was first recorded in 1909, but the first official timber sale was not issued until 1914. Manufacturing profiles have changed drastically over the years from the early tie mills and the first sawmill in South Fort George built in 1909 by the Fort George Lumber and Navigation Company. The 'bush mill* era saw several hundred small sawmills throughout the region established within close proximity of their timber source. At present the forest industry is maintained by several highly integrated and sophisticated forest products companies, their suppliers and their marketing outlets (Runnalls 1946; Smith 1950; Dobbs 1972; Annon. 1980; Bernsohn 1980). Initially, selective logging used stem form and diameter limits as selection criteria in the mature uneven-aged spruce-subalpine f i r stands of the area. Diameter limit logging generally provided that a l l trees of 30 centimetres (cm) diameter at breast height (dbh) and over 50% sound wood were to be removed. The residual stand and advance growth was to supply the second cut; the third cut depended upon advance growth and regeneration following the first cut. There were problems with this approach, in that a stand conversion was evolving as the generally larger spruce were removed, to leave a predominantly subalpine f i r stand; the anticipated spruce regeneration did not materialize on the undisturbed forest floor. Single tree selection systems were introduced in the late 1940's in an attempt to provide a more uniform residual stand but were also unsuccessful in their attempts to produce a merchantable second cut and secure spruce regeneration for successive harvests (Fraser and Alexander 1949; Dobbs 1972; Bernsohn 1980). 13 The goal of natural regeneration of spruce was s t i l l maintained as alternate strip clearcutting, utilizing cut and leave strips of 80 to 200 metres in width and up to 600 metres in length, was introduced in the early 1950's. Once again, natural regeneration of spruce on the undisturbed forest floor and a successful release of advanced regeneration was not realized. Scarification of the logged strips and pre-scarification of the leave strips to prepare a seedbed for natural regeneration was attempted and met with moderate success i f a seed crop occurred prior to site invasion by brush (Dobbs 1972; Bernsohn 1980; Revel 1981). Generally unsuccessful attempts at securing natural regeneration of spruce from forestry practices of the times and the issuing of the first close utilization timber sales in the mid 1960's resulted in a trend toward large (80+ hectare) clearcut blocks. Post-harvesting treatment generally consisted of fire hazard abatement and site preparation by broadcast burning followed by ar t i f i c i a l regeneration of spruce by planting (Dobbs 1972; Bernsohn 1980; Revel 1981). While i t was suggested in the report of the 1945 Sloan Commission on the forest resources of British Columbia that planting after logging be increased as a method of achieving sustained yield, i t was almost 20 years later that the first plantation was established in Supply Block 'G' of the T.S.A. Presently, freshly-logged areas are mostly planted. Areas where natural spruce regeneration has been unsuccessful are being treated and planted as funding, planting stock and other resources permit (Anon. 1979; Bernsohn 1980; Revel 1981). 14 All present harvesting in Supply Block 'G' is by clearcutting with the planned post-harvesting treatment of the typical spruce and spruce-subalpine f i r site being a broadcast burn followed by planting. When burning cannot be successfully completed or when i t is not prescribed then mechanical treatment such as scarification, windrowing or piling is generally undertaken where site conditions allow the use of heavy equipment. Some areas are left untreated — not as a planned option, but only when a l l other treatment alternatives are exhausted. The treated areas are scheduled for planting with stock types and provenances ideally matched to site conditions and location while the untreated blocks are generally left, in the vain hope of regenerating naturally, to become Not Satisfactorily Restocked (NSR) or Non Commercial Cover (NCC) (Revel 1981). 1.2.3 Forest Management Strategies Overall T.S.A. stand composition and age class distributions generally dictate a management regime wherein the mature and over-mature spruce and spruce-subalpine f i r forests are harvested and replaced by vigorous spruce plantations. An accelerated harvest in Supply Block 'G' has been necessary since late 1975 in response to widespread blowdown in that year and, since 1979, a massive spruce beetle (Dendroctonus  rufipennis (Kirby)(Coleoptera: Scolytidae)) outbreak (Erickson and Loranger 1984; Wood et al. 1984). Two major constraints have been placed on the harvesting strategies in the Prince George T.S.A.: the minimum 15 stand age for harvest was set at 80 years; and, the minimum stand volume for harvest was set at 175 m3 per hectare (Anon. 1980). There presently appears to be an absence of definite management strategies for the immature forests of not only the Prince George T.S.A. but a l l of British Columbia. Once a spruce plantation has been established, at 1200^ stems per hectare, the closest approximation of any guidelines for expected stocking during the first 50 years of growth is a reference to white spruce growth and performance in eastern Ontario"''. Yield tables have been developed for unmanaged white spruce plantations to 50 years from planting for six establishment spacings and four site index classes at the Petawawa Forest Experiment Station (Stiell and Berry 1973). In the Ministry of Forests' Forest and Range Resource Analysis Technical Report (Anon. 1980) forest management needs relative to the portion of the Prince George Region west of the Rocky Mountains were addressed. The needs for this area, of which the Prince George T.S.A. is a part, were: 1- improved utilization of existing stands; 2- reduction of losses to fire and pests; and, 3- long range silvicultural initiatives such as rehabilitation, tree improvement and increased planting. 1 J.R. Gilmour. Forester. Silviculture Branch. B.C. Forest Service, Victoria, B.C. personal communication. 16 1.3 The Spruce Resource 1.3.1 Taxonomy The precise taxonomy of the spruce occurring in the central interior of British Columbia is uncertain. Variation within and between the native species of spruce has created a complex of botanical types which is found throughout British Columbia (Garman 1957). Though the true nature of the variation cannot be demonstrated by taxonomic studies, Garman (1957) made i t quite obvious that there were variants which exhibit the features of both white spruce and Engelmann spruce (Picea engelmannii Parry). Some authors described the western white spruce (Picea glauca (Moench) Voss var. albertiana (S. Brown) Sarg.) (Fowells 1965; Sutton 1969; Harlow et al. 1979) as the species found in the central interior of the Province but Garman (1957) attributed this variety to a product of natural hybridization between white spruce and Engelmann spruce. Both Garman (1957) and Roche (1967) agreed that the variety albertiana should be discarded since i t , in fact, refers to the white spruce-Engelmann spruce hybrid. Genetic variation, ecotypic response and the species hybridization have created a number of varied populations throughout the range of spruce in the interior of British Columbia rather than a clear-cut species. It seemed quite evident, according to Roche (1967), that both P. glauca and P. glauca x engelmanni have 17 occupied an ecological niche between that of the parental forms. This niche, in British Columbia, is available in the broad transition zone between the low elevation P. glauca of the montane forest and the high elevation P. engelmanni of the subalpine forest. The selection pressures -associated with altitudinal change generally vary progressively and, as one would expect, the transition from pure P. glauca through the hybird swarms to pure P. engelmanni will also be progressive. Roche (1967) demonstrated this progression through the use of transects in the Stone Creek area, south of Prince George. Garman (1957) indicated that generally the populations east of the Cascade Mountains vary from Engelmann spruce in the south, and probably through British Columbia at high elevations, to white spruce at or near base levels in the central and northern part of the Province. Krajina et al. (1982) maintained that two species existed based on an altitudinal separation. Meidenger"'' suggested that the spruce in the southern portion of the Prince George Forest Region (i.e. - the Prince George T.S.A.) is the hybrid P. glauca x engelmanni even though i t is commonly called white spruce and very often referred to as interior spruce (Stiell 1976). The silvical characteristics are generally considered to be similar to those of P. glauca. 1.3.2 Habitat Conditions White spruce has a transcontinental distribution, occurring in D. Meidenger. Forest Ecologist. B.C. Forest Service, Research Branch. Victoria, B.C. personal communication. 18 British Columbia in the boreal forest as far west as the Cascade Mountains and as far north as the limit of trees at elevations from sea level to over 1700 metres. It grows under a wide range of conditions — from the wet Maritime climate of Nova Scotia, where i t experiences more than 125 cm annual precipitation to the semi-arid conditions of southern Manitoba with less than 25 cm annual precipitation. It is a very hardy tree, capable of enduring temperatures from -55°C to +45°C with mean daily July temperatures between +13°C and +21°C. The growing season varies from 160 days in Maine to as short as 20 days in the northern ranges. Generally, however, i t grows south of a line indicating a growing season of 60 days with a considerable part of its range falling within the permafrost zone (Fowells 1965). White spruce grows on a variety of soils of glacial, lacustrine, marine or alluvial origin (Fowells 1965) but makes its best growth on moist alluvial soils (Anon. 1966; Cayford and Bickerstaff 1968). It will tolerate a wide range of moisture conditions but its growth will be .stunted and scrubby on both too wet and too dry soils. For maximum development i t requires a supply of well-aerated water (Nienstaedt 1957). Flood resistance of white spruce is high so that i t is able to become established and thrive in alluvial habitats which are frequently flooded (Krajina et al. 1982). Sutton (1969) reported that, while white spruce can withstand short periods of flooding, long term flooding of 60 days killed stands of 4.5 metres in height and 30 days of flooding resulted in mortality to individuals between 30 and 60 cm in height. 19 Powells (1965) indicated that white spruce is very exacting in its nutrient requirements with deficiency symptoms including stunting of its growth and yellowing and early-dropping of its needles. It does, however, respond well to fertilizer treatments. This species will tolerate a wide range in pH — from 4.5 to 8.4 — with its optimum range being 5.0 to 6.0 (Nienstaedt 1957). Forest fires, in the natural environment, and prescribed burning, in the managed forest situation, promote regeneration of white spruce stands by causing rapid decomposition of organic materials, which reduces acidity to levels which can support thrifty white spruce stands (Krajina et al. 1982). White spruce occurs naturally in extensive pure stands but is commonly found in mixtures with subalpine f i r , lodgepole pine, Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western redcedar (Thuja plicata Donn), western hemlock (Tsuga heterophylla (Raf.) Sarg.), black spruce (Picea mariana (Mill.) BSP.), trembling aspen (Populus  tremuloides Michx.), balsam poplar (Populus balsamifera L.), black cottonwood (Populus trichocarpa Torr. and Gray) and western white birch (Betula papyrifera Marsh, var. commutata (Regel) Fern) throughout its range in British Columbia. 1.3.3 Life History Flowering occurs in May and June, depending upon environmental 20 factors, and lasts for up to five days. The cones ripen in late August and first open in mid-September with most of the seed being shed within nine weeks of opening (Fowells 1965). Seed production starts at age 30 to 40 but can occur on trees as young as 15 years of age. White spruce produces good crops of seed every two to seven years with light crops in the intervening years. Seed dispersal has been observed to be about 100 metres but strong winds are likely to extend this to over 500 metres. Germination takes place in June and July of the year following seed dispersal, once the seedbed temperatures become favourable. Seedbed moisture retention is critical to seedling development since the germinant is very small and has shallow root penetration. Mineral soil is the best seedbed since i t generally maintains a relatively constant moisture level throughout the early growth of the germinant. While white spruce will frequently germinate in moss, litter, humus and decayed logs, the overall survival and growth is far superior in mineral soil (Fowells 1965). Although considered a low to moderately shade tolerant species (Krajina et al. 1982), white spruce, in part because of its small size in the first few years, is unable to compete with dense perennial growth and is very difficult to maintain where i t is growing in a mixture with hardwood species (Nienstaedt 1957). A heavy brush cover also creates an ideal habitat for the snowshoe hare which will, in times of peak populations, damage nearly a l l young trees (Fowells 1965). Therefore i t is often necessary to reduce or eliminate brush cover and competition i f 21 white spruce survival and growth is to be maximized in its early years. Once established, white spruce is relatively shade-tolerant (Sutton 1969). White spruce grows rapidly in its early years i f ideal nutrient regimes and sunlight conditions are available (Harlow et, al. 1979). However, being a relatively tolerant species, i t will survive 40 or 50 years of suppression and s t i l l show growth response when released (Lees 1966; Steneker 1967; Sutton 1969). Where white spruce grows with hardwoods established at the same time i t will f a l l behind and remain an understory tree until i t is released (Neinstaedt 1957; Lees 1966; Steneker 1967). In coniferous mixtures i t will maintain growth with and eventually exhibit dominance over the other conifers. Leader dimensions of immature spruce trees, commonly 0.75 cm in diameter and 30 cm long, can be as large as 2.0 cm in diameter and as long as 60 cm. Mature trees may be as t a l l as 60 metres but are more commonly in the 35 metre range with a diameter at breast height of 60 cm. Yields at current harvest age of 300 cubic metres per hectare (irfVha) are not uncommon on the better sites in the Prince George T.S.A. with individual 3 3 tree volumes commonly greater than 1.0 m and as high as 1.5 m . Maximum mean annual increments for pure spruce stands (volume net for decay only; close utilization standards; 17.5 cm diameter at breast 3 3 3 height and greater) are 4.1 m /ha/yr, 2.9 m /ha/yr and 1.2 m /ha/yr for good, medium and poor sites, respectively (Anon. 1978). 22 1.3.4 Growth of Planted Spruce White spruce is the most widely planted tree species in Canada (Cayford and Bickerstaff 1968; Stie l l 1976). It occurs naturally over a large portion of Canada and, therefore, constitutes an important forest products resource. White spruce is quite often the only species suitable for reforesting sites denuded by logging or wildfire. Its satisfactory performance over a wide range of site types makes i t an ideal candidate for planting programmes. The first recorded forest planting of white spruce was in 1908 in Ontario, followed by one in Quebec in 1912. Extensive planting of the species was conducted by the Laurentide Company in Quebec between 1919 and 1931 (Sutton 1969; Stiell 1976). It was not until the late 1950's that the first spruce plantation was established in the central interior of British Columbia. Newly planted seedlings are very vulnerable to adverse factors of the environment. Stiell (1976) noted that the majority of mortality took place in the first four years after planting. He attributed the mortality factors to those associated with site or weather (drought, frost heave, flooding, exposure), establishment (planting faults, stock size, non-dominant stock) and competition (principally from grasses). Five-year survival rates for plantations in Ontario were reported to average 61% for bare-root and 33% for tubed seedlings. Revel (1981) reported, for plantations of interior spruce established subsequent to satisfactory site preparation, two-year survival figures of 85% for 23 bare-root and 90% for container seedlings. Five-year survival figures were generally in the 75% range for similar sites. It has been widely accepted that, in addition to spruce being a slow-starting species, a period of 'check' or 'planting shock' further suppresses the i n i t i a l growth of planted spruce (Dobbs 1972; Stiell 1976). Sti e l l (1976) reported that this 'planting check' was not caused directly by root damage or deep planting, but was most likely a result of nutrient stress from the roots' inability to develop in the planting zone. Height growth was often found to be delayed and irregular in the first 15 years and, consequently, site index curves could not be extended with any reliability into the early years of plantation growth (Stiell 1976). Sti e l l and Berry (1973) determined that mortality caused by mutual competition was not a factor in stands established at 1200 stems per hectare until a dominant height of 12 metres was attained. Planted white spruce bare-root seedlings averaged 61 cm t a l l five years after planting in Ontario (Stiell 1976). Draper (1983) reported a 50 cm height five years after planting and 145 cm ten years after planting for interior spruce seedlings in the Prince George Forest Region. He noted that plantations established after 1970 reached breast height after eight years, while those established prior to 1970 required nine to ten years to achieve the same height. The apparent trend was attributed to improved stock quality, better planting quality, improved site preparation and other minor factors. 24 1.4 Study Objectives As a significant proportion of the productive forest land in the Prince George T.S.A. is best suited to supporting spruce forests and as the present and future dependence upon spruce forests will increase rather than decrease, this species has been chosen as the topic of this study. Forest industrial operations in the Prince George T.S.A. are dependent upon spruce forests for their livelihood. The spruce component of the T.S.A. short-term net merchantable volume exceeds 50% of the total for three Supply Blocks (Table II). The total short-term net merchantable volume of mature spruce in the T.S.A. is 311 745 420 m"5 or approximately 42% of the total (Table II) (Anon. 1979). The overall objective of this study was to evaluate the insect and disease risk factors to successfully growing spruce plantations through the in i t i a l period of maximum susceptibility (Fig. 1) to a merchantable crop in the Prince George T.S.A. There were four sub-objectives: 1- To review available literature and collection records to identify potentially damaging insects and diseases that have been reported in the established interior spruce plantations of the Prince George T.S.A.; 2- To survey spruce plantations that were established in 1973 or earlier in Supply Block 'G' of the Prince George T.S.A. to determine the presence and relative incidence of pests; Table II - Short-term (20 year) net merchantable timber supply by species and Supply Block in the Prince Prince George T.S.A. From Prince George Timber Supply Area Yield Analysis Report (Anon. 1979). Supply Block Species 1 % Volume (m3) PI S B C H F Decid. Spruce Total A 8.37 18.96 70.40 1.88 0.37 865 088 45 612 698 B 28.21 36.67 33.43 0.17 1.47 47 892 366 130 603 671 C 48.27 37.72 7.13 4.34 2.91 39 791 252 106 621 790 0 67.14 25.38 5.25 1.03 1.17 26 695 118 105 181 719 E 30.25 54.55 11.20 1.74 2.24 67 964 407 124 519 036 F 62.11 22.50 1.74 11.21 2.40 7 368 502 32 748 896 G 13.72 68.07 13.56 0.09 0.51 2.20 1.81 59 713 455 87 723 601 H 0.89 58.03 24.22 10.29 3.22 1.55 1.74 58 976 922 101 631 781 I 52.77 30.92 3.71 8.78 3.78 2 478 310 8 015 232 1 Symbols for tree species: PI, lodgepole pine; S, spruce: B, balsam (Subalpine f i r ) ; C, cedar; H, hemlock; F, Douglas-fir; Decid, deciduous (aspen, b irch, cottonwood). 26 3- To develop a scenario for the successful growth of spruce to a merchantable crop through the analysis of pest incidence, pest impact, available control methods and spruce silvicultural techniques; and, 4- To detail immediate and future requirements for an integrated intensive forest management programme. A thorough understanding of host/pest relationships in the immature forest is necessary in management systems to minimize the economic impact of pests and to maximize the stand merchantability at harvest. This thesis aims to supply the necessary background and identify areas requiring further action essential to the formulation of well-informed forest management decisions. Supply Block 'G' (Fig. 2) of the Prince George T.S.A. was selected as the study area as i t contained the majority of the older spruce plantations following the forest harvesting which has been concentrated in this area for many years. This Supply Block supports a substantial volume of mature spruce (Table II) and has a large proportion of its area best suited to the growth of spruce forests. The Prince George T.S.A. Yield Analysis Report (Anon. 1979) indicated that this Supply Block will, over the next 20-year period, supply annually 1 658 950 m3 of harvest, almost 22% of the T.S.A. short-term timber supply. 27 2. METHODS 2.1 Literature and Information Compilations Prior to the field collection of pest incidence data, systematic literature surveys were undertaken to ascertain the pests — insect and disease — that may be present in the spruce plantations that were to be surveyed. With the knowledge of the pests that may be present, plantation surveys and individual tree examinations could be conducted in such a manner as to ensure that the chances of observing the signs of the activity of any particular pest were optimized. While there certainly may be recordings of insects or pathogens that were not included in the summaries, i t is unlikely that the damage inflicted will deem many of them to be significant forest pests. 2.1.1 Insect Pests Reference material specifically relating to the occurrence of insect pests in immature stands of interior spruce was not located. Furniss and Carolin (1977) addressed a wide range of forest insects and their damage on the trees of western North America. A summary of the insect pests that may be active in and of potential importance to the growth of the immature spruce stands of the central interior of British Columbia was compilied from this work. Rangers of the Forest Insect and Disease Survey (FIDS) section of the Canadian Forestry Service have been routinely surveying the 28 forests of the Prince George Forest Region since 1949, recording forest pest incidence and damage. The actual incidence of forest insects discovered in their surveys was considered to be a more reliable indication of the insect pests that may be expected to be active in the spruce plantations to be surveyed. Pest collection records were obtained from the Pacific Forest Research Centre, analysed and summarized to present the occurrence of insect pests species relative to forest tree maturity classes as defined by FIDS. 2.1.2 Forest Diseases Literature describing the incidence of forest diseases and their impact upon spruce in the central interior of British Columbia is quite limited. The works of several authors were reviewed to summarize the pathogens that may occur on immature interior spruce (Boyce 1961; Foster and Wallis 1969; Baranyay and Ziller 1972; linger 1972; Whitney 1972, 1977; Morrison 1976, 1981; Funk 1978; Holsten et al. 1980). FIDS records were reviewed with the same rationale and in the same manner as described in Section 2.1.1. General descriptions of the activity of the various pathogens were obtained from FIDS; damage ratings, however, could not be applied realistically or confidently to their activity due to the lack of proper studies on specific pathogen activities, distribution, incidences and intensities that are required to 29 produce properly researched ratings . 2 . 2 Field Survey of Spruce Plantations The determination of the relative incidence of the major pests active in the spruce plantations of Supply Block 'G' and the numbers of healthy, potential crop spruce trees was accomplished through actual plantation surveys. Only pure spruce plantations and those portions of mixed-species plantations containing pure spruce were considered as suitable candidates for the survey (Table III). Since a 1free-to-grow1 status was desired, to reduce the influence of brush competition upon tree vigour and, perhaps, resistance to pest attack, only those plantations established in 1973 or earlier were candidates for this study (Table III; Fig. 4). A continuous strip survey, where a l l trees within a five metre width were assessed and tallied, was judged to provide the most reliable data and yet allow the survey to be completed within practical and economic limits. The desired minimum sampling intensity was set at 0.5% of the plantation area and strips were located to achieve this target level. Since this was a minimum level, survey lines were often longer than necessary to achieve the 0.5% level, to ensure representative coverage of the plantations surveyed. All points-of-commencement, Dr. J. Hopkins. Pathologist. Forest Insect and Disease Survey. Pacific Forest Research Centre, Canadian Forestry Service. Victoria, B.C. personal communication. Table III - Spruce 1 ! 2 plantation l i s t i n g 3 for Supply Block 'G ' in the Prince George Timber Supply Area for plantations established i n 1973 or ear l ie r . YEAR OF ESTABLISHMENT PROJECT NO. LOCATION AREA (ha) OF SPRUCE COM>£NTS 1963 93G16-01 Jeep Lake 13 Surveyed 1983 (stand 1A) 4 1964 1965 1966 1967 93G01-O1 93G16-02 93G16-03 93G16-04 93G16-05 93G16-06 93G08-01 93G08-O2 Genevieve Lake Wansa Lake Wansa Lake Buckhorn Lake Buckhorn Lake Buckhorn Lake Genevieve Lake Neck Lake 22 36 35 157 35 72 45 88 very l ight Adelges and Pissodes (Walsh 1980b) surveyed 1983 (stand 14) very l ight Adelges (Walsh 1980b) Surveyed 1983 (stand 14) 25% of planted trees suppressed; most infested with Adelges (Walsh 1980D) Surveyed 1983 (stand 12) rabbit damage throughout; l ight Adelges (Walsh 1980b) Surveyed 1983 (stand 12) planted spruce sparse (Walsh 1980b) severe ga l l aphid; stem aphids throughout; some Pissodes (Walsh 1980a) 93G16-07 Corless Creek 134 Table III - Continued YEAR OF ESTABLISHMENT PROJECT NO. LOCATION AREA (ha) OF SPRUCE COMMENTS 1968 93G08-O3 Neck Lake 91 extensive g a l l aphid; Pissodes damage evident (Walsh 1980a) 93G08-O4 Neck Lake 77 planted spruce d i f f i c u l t to locate; heavy ga l l aphid damage; cnlorot ic seedlings (Walsh 1980a) 93H05-02 Stony Lake 73 1969 93G01-15 Genevieve Lake 24 s tr ip logging; plantation boundaries d i f f i c u l t to determine therefore not surveyed 93G01-16 Ahbau Creek 26 93G08-05 Genevieve Lake 103 93G09-08 Grizzly Lake 119 Surveyed 1983 (stand 4) 93G10-09 Stone CreeK 13 93G16-08 Corless Creek 45 "NSR" 93G16-09 Corless Creek 100 rabbit damage severe; l ight to moderate Adelges on a l l trees (Walsh 1980b); "NSR" 93J01-03 Aleza Lake Forest 130 Table III - Continued YEAR OF ESTABLISHMENT PROJECT NO. LOCATION AREA (ha) OF SPRUCE COMMENTS 1970 1971 93G08-06 93G09-09 93G16-10 Ross Lake Grizzly Lake Corless Creek 93G16-11 Corless Creek 93G16-13 Vama Varna Creek 93G16-14 Wansa Creek 93G08-07 Mary Lake 93G09-10 Wansa Creek 128 16 88 123 41 91 93G16-15 Vama Vama Creek 117 243 162 Surveyed 1983 (stand 2) Surveyed 1983 (stand 1) severe rabbit damage; l ight Adelges; leader damage from unknown cause (Walsh 1980b); "NSR" heavy rabbit damage; widespread Adelges; leader damage from unknown cause (Walsh 1980b); "NSR" l ight Adelges; patchy Pissodes (Walsh 1980b) Surveyed 1983 (stand 9) chlorosis throughout; l ight Adelges and Pissodes (Walsh 1980b) Surveyed 1983 (stand 13) Adelges widespread; patchy Pissodes (Walsh 1980b) Surveyed 1983 (stand 9) Surveyed 1983 (stand 8) Table III - Continued YEAR OF ESTABLISHMENT PROJECT NO. LOCATION AREA (ha) OF SPRUCE COMMENTS 1971 93G09-13 Ispah Lake 67 93G16-16 Wansa Creek 37 93G16-17 Vama Vama Creek 46 93G16-19 Vama Vama Creek 60 93J01-O4 Aleza Lake Forest 8 93J01-05 Aleza Lake Forest 176 Surveyed 1983 (stand 10) l ight Adelges on a l l trees; Pissodes present (Walsh 19800) Surveyed 1983 (stand 13) moderate Adelges (Walsh 1980b) Surveyed 1983 (stand 11) s l ight Adelges; small amount of Pissodes (Walsh 19805) Surveyed 1983 (stand 9) 1972 1973 93H13-09 93G08-09 93008-10(0) 93G08-10(E) 93G08-11 North Purden Neck Lake Ahbau Lake Ahbau Lake Hudson Lake 134 107 40 20 78 Surveyed 1983 (stand 3) Surveyed 1983 (stand 7) Surveyed 1983 (stand 6) Table III - Continued YEAR DF ESTABLISHMENT PROJECT NO. LOCATION AREA (ha) OF SPRUCE COMMENTS 1973 93G09-17L Francis Lake 34 93G09-18L Pitoney Lake 16 93G09-19L Pitoney Lake 10 93G09-20L Pitoney Lake 30 93G16-24 North Purden 26 l i t t l e Adelqes evident - usually on leader (Walsh 1980b) surveyed 1983 - spruce sparse 93G16-25L North Purden 117 mainly pine planted Surveyed 1983 (stand 5) 93H13-15L North Purden 109 surveyed 1983 - primarily pine 93J01-07 Aleza Lake Forest 30 1 Spruces of economic Importance in central B r i t i sh Columbia include Picea glauca, Picea engelmannii and Picea glauca x engelmannii. 2 Spruce is either the only species planted or the leading species in a mixed plantation 3 Plantations established in 1973 or ea r l i e r . 4 Table VIII summarizes the condition of the stands surveyed in 1983 as a part of th i s project. 35 Figure 4- Location of spruce plantations established i n 1973 or e a r l i e r i n Supply Block 'G' of the Prince George Tionber Supply Area. 36 turning points, points-of-termination and survey lines were located on 1:20 000 panchromatic aerial photographs to facilitate identification and location of problem areas for further assessment or treatment. Data were recorded and summarized for each 100 metres of survey line. Examples are provided in Appendices I, II and III. Descriptive statistics of plot and stand data were calculated using the statistical package MIDAS (Fox and Guire 1976) at the University of British Columbia Computing Centre. Profiles of current pest status in the examined stands were developed. 3. RESULTS 3.1 Literature and Information Compilations 3.1.1 Insect Pests A review of the forest insect pests described by Furniss and Carolin (1977) indicated 29 insect species in nine families that have been recorded as potential pests of immature interior spruce in the central interior of British Columbia (Table IV; Fig. 5). Of the insects listed, only a small number appeared to be potentially detrimental to growth and survival of interior spruce. Tree mortality has resulted from root collar girdling by Hylobius warreni Wood (Coleoptera: Curculionidae) while severe tree deformation or growth reduction can be a result of the activity of Pissodes strobi or Rhabdophaga swainei Felt Table IV - Insect pests of immature spruces! that may occur i n central B r i t i sh Columbia. From Furniss and Carolin 1977. Order Family Genus/Species Common Name Comments Coleoptera Curculionidae Hylobius warreni Wood Pissodes strobi (Peck) Diptera Cecidomyiidae Rhabdophaqa swainei Felt Homoptera Aphididae Cinara coloradensis (Gi l lette) Cinara fomacula Hottes Phylloxeridae Adelqes ablet is (L.) Adelqes cooleyi (Gi l lette) Plneus boycel Annand Pineus p in i fo l iae (Fitch) Pineus s imi l i s (Gi l lette) Hymenoptera Tenthredinidae Pikonema alaskensis (Rohwer) Lepidoptera Geometridae Caripeta anqustiorata Walker Caripeta divisata Walker Ectropis crepuscularia (Denis 4 Schiffermuller) Ep i r r i ta autumnata omissa Rarrisson Lambdina f i s ce l l a r i a f i s ce l f a r i a (Guenee) Warrens' co l l a r weevil white pine weevil^ spruce bud midge green spruce aphid eastern spruce ga l l adelgid Cooley spruce ga l l adelgid pine leaf chermid yellow-headed spruce sawfly gray pine looper gray forest looper saddleback looper green velvet looper hemlock looper complete g i rd l ing k i l l s t ree; pa r t i a l g i rd l ing provides in fect ion entrance point k i l l s terminal ultimately reducing merchantability of tree mines and k i l l s terminal buds heavy infestations of Cinara spp. cause yellowing of foliage and can reduce growth on small trees ga l l s formed as a result of Adelqes and Pineus spp. attack can be a factor i n growth reduction in young plantation trees damages and sometimes k i l l s spruce by defol iat ion prefers pines but attacks spruces a sol i tary feeder on many tree species prefers hemlock but w i l l feed on spruces potent ia l ly damaging; two minor out-breaks recorded Table IV - continued Order Family Genus/Species Common Name Comments Melanolophia imitata (Walker) greenstriped forest looper part icu lar ly destructive but prefers humid areas; mainly attacks western hemlock on the coast Nepytla canosaria, (Walker) false hemlock looper rarely occurs west of Rockies; more often N. freemani in B.C. Nepytia freemani Munroe prefers Douglas-fir but w i l l feed on spruce; loca l minor outbreaks in pole and sapling-sized stands Nyctobia l imi tar ia (Walker) yellowlined forest looper a so l i tary feeder; potent ia l ly destructive though no major outbreaks recorded Lymantriidae Orqyia antiqua (L.) rusty tussock moth mainly attacks western hemlock on the coast Parorgyia grisefacta (Dyar) pine tussock moth mainly found in immature pine Pyralidae Dioryctria abiet ivorel la (Grote) Dioryctria pseudotsuqella Munroe f i r coneworm pr inc ipa l ly feeds in cones but often attacks shoots feeds on shoots, fol iage and cones Dioryctr ia reniculel loides Mutuura 4 Munroe spruce coneworm feeds on cones, fol iage and flowers Tortricidae Acler is qloverana (Walsingham) western blackheaded budworm an important forest defo l iator Choristoneura biennis Freeman 2-year budworm widespread in central B.C. but not economically s ign i f icant as yet Choristoneura fumiferana (Clemens) spruce budworm potentia l ly an important defol iator Choristoneura occidentalis Freeman western spruce budworm the most destructive defo l iator in N. America 1 Spruces of economic importance in central Br i t i sh Columbia include Picea glauca, Picea engelmannii and Picea glauca x engelmannii. 2 While the correct common name associated with P. strobi i s white pine weevil, i t i s referred to in B r i t i s h Columbia as the spruce weevil since i t attacks spruces - white, Engelmann and Sitka - and does not attack western white pine in B.C. (McMullen 1976). 39 F i g u r e 5- General areas o f a c t i v i t y o f major p e s t s o f irrmature i n t e r i o r spruce t r e e s . 40 (Diptera: Cecidomyiidae). Pikonema alaskensis (Rohwer) (Hymenoptera: Tenthredinidae) was described as a defoliator capable of killing immature spruce trees. Heavy infestations in successive years by Adelges spp. or Pineus spp. (Homoptera: Phylloxeridae) can be a factor in the reduction of growth in young plantation trees. Based on the Maritimes experience (Sterner and Davidson 1983), the bud moths (Zeiraphera spp.) should not be discounted as potentially important pests of spruce plantations in British Columbia. FIDS records during the period 1949 to 1982 indicated at least 69 species in 16 families that had been collected and identified as pests or potential pests of immature spruce in the Prince George T.S.A. (Table V; Fig. 5). Incidence records were readily summarized but damage ratings were not available, which prevented an estimation of the relative importance of the insects detected. Both the ratings of the damage inflicted upon the host and the numbers of insects present at the time of sampling are necessary to determine the relative importance of a number of pests. 3.1.2 Forest Diseases The review of literature indicated that 21 species of pathogens in six orders may be potential pests of immature interior spruce in the central interior of British Columbia (Table VI; Fig. 5). Of the pathogens listed, only the root rots, Armillaria mellea (Fr.) Kumm., Fomes annosus (Fr.) Cke. (Basidiomycetes: Agaricales) and Polyporus Table V - Insect pests of immature* spruces 2 recorded in Forest Insect and Disease Survey records for the Prince George Timber Supply Area (Anon. 1983 3). Insect Pest Number of Collections by Maturity C la s s 1 Order Family Genus/Species Common Name 3 4 5 6 Coleoptera Curculionidae Hylobius spp. 2 Hylobius piceus Deq. 2 Hylobius warreni Wood Warren's co l l a r weevil 1 Pissodes spp. 1 9 16 Pissodes enqelmami Hopkins Engelmam spruce weevil 1 13 10 Pissodes schwarzi Hopkins 3 Pissodes strobi Peck* spruce weev i l 5 5 8 5 Pissodes terminalis Hoppinq lodgepole terminal weevil 1 Oiptera Cecidomyiidae Mayetiola carpophaqa (Tripp) 1 Rhabdophaqa swainei Felt spruce bud midge 1 Homoptera Aphididae 2 1 Cinara spp. giant conifer aphids 4 6 Phylloxeridae Adelqes abiet is (L.) eastern spruce ga l l adelgid 1 Adelqes cooleyi (Gi l lette) Cooley spruce g a l l adelgid 2 14 23 Pineus spp. 1 3 5 Pineus p in i fo l iae (Fitch) pine leaf chermid 1 Pineus s imi l i s (Gi l lette) 1 Hymenoptera Diprionidae conifer sawflies 1 Neodiprion spp. 22 114 Neodiprion tsuqae Middleton hemlock sawfly 1 Plkonema spp. 4 26 Plkonema alaskensis (Rohwer) yellowheaded spruce saw f ly 19 234 Pikonema dimmockii (Cresson) greenheaded spruce sawfly 33 270 Pikonema rura l i s (Cresson) 2 Table V - Continued Insect Pest Number of Col lections by Maturity C las s 1 Order Family Genus/Species Common Name 3 A ' 5 6 Pamphiliidae webspirming sawflies - 2 37 Acanthulyda spp. 2 23 Cephalcia spp. 6 Tenthredinidae sawflies 2 27 Lepidoptera Arcti idae t iger moths 1 Gelechiidae Eucordylea aturp icte l la Dietz needle miners 5 19 Geometridae 1A 57 Caripeta spp. 17 Caripeta anqustiorata Walker gray pine looper 2 Caripeta divisata Walker gray forest looper 2 31 Ectropis crepuscularia (Denis saddleback looper 3 3A and Schiffermuller) Ep i r r i ta autumnata Gn. A 10 Ep i r r i t a autumnata omissa green velvet looper 2 12 Harrisson Ep i r r i ta pulchraria (Taylor) whitelined looper 2 A Eupithecia spp. 1A 88 Eupithecia albicapitata Pack. 1 Eupithecia amulata (Hulst) 2 7 Eupithecia fllmata Pears. A 21 Eupithecia qelidata Moesch. 1 Eupithecia kasloata Dyar 1 Table V - Continued Insect Pest Number of Col lections by Maturity C la s s 1 Order Family Genus/Species Common Name 3 4 5 6 Eupithecia luteata bifasciata uyar 4 32 Eupithecia palpata Pack. 1 Eupithecia transcanadata Mack. 1 18 Lambdina f i s c e l l a r i a lugubrosa (Hulst) western hemlock looper 5 31 Nyctobia l imi tar ia (Walker) yellowlined forest looper 12 54 Nyctobia l imi tar ia nigroangulata Stkr. 1 2 Operophtera bruceata (Hulst) Bruce spanworm 2 Protoboarmia porcelaria indicatar ia Walker 2 13 Semiothisa spp. 1 16 Semiothisa'granitata Gn. 5 50 Semiothisa signaria unipunctaria Wgt. 3 32 Lasiocampidae Malacosoma d i s s t r ia Hubner forest tent ca te rp i l l a r 3 Lymantriidae Orgyia antigua badia Hy. Edw. 8 4 Noctuidae Actebia fennica (Tauscher) black army cutworm 7 10 47 Olethreutidae Griselda spp. Griselda radicana (Heinrich) Zeiraphera spp. Zeiraphera destitutana (Walker) Zeiraphera fortunana Kft. spruce t ip moth bud moths 4 7 9 6 5 6 3 41 32 20 63 Pyralidae Dioryctria spp. Dioryctr ia ponderosae Dyar ponderosa twig moth 1 1 Table V - Continued Insect Pest Number of Col lections by Maturity C las s 1 Order Family Genus/Species Common Name 3 4 5 6 Dioryctria reniculel loides Mutuura 4 Munroe spruce coneworm 1 Tortricidae Acler is spp. lea f ro l le r moths 2 25 7 Ac ler i s qloverana (Walsinqham)6 western blackheaded budworm 13 57 Ac ler i s variana (Fernald)^ eastern blackheaded budworm 30 168 Arqyrotaenia occultana Freeman 1 . Archips spp. 3 Archippus strianus Fern. 3 Choristoneura spp. 2 4 Choristoneura biennis Freeman7 2-year budworm 1 4 5 Choristoneura fumiferana (Clemens)7 spruce budworm 11 192 1 Listed by FIDS age classes: 3(forest seedling); 4 (sapling); 5 (young growth); 6 (semi-mature). 2 Spruces of economic importance in central Br i t i sh Columbia include Picea glauca, Picea engelmannii and Picea glauca x engelmannii. 3 Based on col lect ions by FIDS Rangers between 1949 and 1982; 17,191 entries for age classes 3, 4, 5 and 6 for a l l species in Prince George Forest Region. 4 While once considered as two species - the Engelmann spruce weevil attacking white and Engelmann spruce and the Sitka spruce weevil attacking Sitka spruce - genetic studies have shown that they are not only the same species but that the spruce weevil and the white pine weevil of eastern forests are also the same species (Wood and McMullen 1983). 5 while the correct common name associated with P. strobi i s white pine weevil i t i s referred to in B r i t i s h Columbia as the spruce • weevil since i t attacks spruces - white, Engelmann and Sitka - and does not attack western white pine in B.C. (McMullen 1976). 6 A. variana was reported up to 1970 and from 1971 a l l reports were ident i f ied as A. qloverana. This suggests a taxonomic problem and not occurrences of A. variana west of the Rocky Mountains. 7 C. fumiferana was reported only up unt i l 1966. After that date a l l reports were C. biennis which suggests a taxonomic name change and ~ that both names refer to the same insect. Table VI - Forest diseases of immature spruces 1 that may occur i n centra l B r i t i sh Columbia. Class Order Genus/Species Comments References Ascomycetes Phacidiales Pleosporales Sphaeriales L i ru la macrospora (Hartig) Darker L i ru la brevispora Z i l l e r Lophodermium plceae (Fckl.) Hoehn. Isthmlella crepidiformis (Darker) Darker Lophomerun darkeri Ouellette Botryosphaeria plceae Funk Herpotrlchia juniper i (Duby) Petr. Epipolaeum tsugae (Dearn.) Schoem. needle cast; strongly paras i t ic Unger 1972 needle cast needle cast; weakly paras i t ic needle cast needle cast branch canker 'snow mould'j k i l l s fo l iage needle disease Unger 1972 Unger 1972 Unger 1972 Unger 1972 Foster 4 Wall is 1969; Funk 1978 Foster 4 Wallis 1969; Unger 1972 Unger 1972 Basidiomycetes Agaricales Polyporales Uredinales Armil laria mellea (Fr.) Kumm. root rot Fomes annosus (Fr.) Cke. root rot Polyporus tomentosus Fr. root rot Chrysomyxa arctostaphyli Diet. broom rust Chrysomyxa chlogenls Diet. needle rust Chrysomyxa empetri Schroet. needle rust Chrysomyxa ledico la Lagerh. needle rust Chrysomyxa we i r i l Jacks needle rust Chrysomyxa woroninli Tranz. shoot rust Perldermium coloradense (Diet.) broom rust Arth. 4 Kern Pucciniastrum americanum (Farl.) Arth. needle rust Pucciniastrum arcticum Tranz. needle rust Boyce 1961; Foster 4 Wallis 1969; Morrison 1976, 1981 Boyce 1961; Foster 4 Wallis 1969 Boyce 1961; Whitney 1972, 1977 Foster 4 Wall is 1969; Baranyay 4 Z i l l e r 1972; Holsten et a l . 1980 Boyce 1961 Boyce 1961 Boyce 1961; Foster 4 Wallis 1969; Holsten et a l . 1980 Boyce 1961 Boyce 1961 Boyce 1961 Boyce 1961 Boyce 1961 Table VI - continued Class Order Genus/Species Comments References Coelomycetes Sphaeropsidales Slrrococcus strobi l inus Preuss. shoot blight Holsten et a l . 1980 Cause unknown target canker Funk 1978 1 Spruces of economic importance in central Br i t i sh Columbia include Picea glauca, Picea engelmannii and Picea glauca x engelmanni1. 47 tomentosus Fr. (Basidiomycetes: Polyporales), may cause mortality to young plantation trees or severe growth reduction and possibly mortality to older immature trees. The remaining pathogens that may occur on immature interior spruce were primarily needle casts and needle rusts and were not described as being major factors in tree growth and survival by Boyce (1961), Foster and Wallis (1969), Baranyay and Ziller (1972) and Holsten et al. (1980). A review of the FIDS records showed that at least 16 pathogen species in five orders had been identified and recorded as potential pests of immature spruce in the Prince George T.S.A. (Table VII; Fig. 5). Only the presence of the pathogens was recorded and, therefore, their relative importance could not be established from these records. 3.2 Field Survey of Spruce Plantations During the summer and early autumn of 1983, systematic field surveys of 14 immature stands, comprised of 22 plantations established between 1963 and 1973, were conducted in Supply Block 'G' of the Prince George T.S.A. Direct, identifiable tree mortality was observed only four times and was attributed to either Hylobius warreni or Armillaria mellea (two occurrences of each). Damage caused by Pissodes strobi to the leaders of young interior spruce was prevalent throughout the plantations as was terminal bud damage caused by a bud midge (Diptera: Cecidomyiidae), likely Rhabdophaga swainei (Table III; Table VIII; Table IX; Fig. 6). Survey summaries and copies of aerial photographs showing Table VII - Forest diseases of immature1 spruces 2 recorded i n Forest Insect and Disease Survey records for the Prince George Timber Supply Area (Anon. 1983 3). Forest Disease Number of Col lect ions by Maturity C las s 1 Class Order Genus/Species Comments 3 4 5 6 Ascomycetes Helotiales Naevia piniperda Rehm Tryblidiopsis p inastr i (Fr.) Karst. needle bl ight weak branch dieback 1 1 1 Phacidiales L i ru l a spp. L i ru la macrospora (Hartig) Darker Lophophacidium hyperboreum Lager. needle cast snow bl ight 1 3 1 4 Pleosporales Botryosphaeria piceae Funk stem canker 1 Basidiomycetes Uredinales Chrysomyxa spp. Chrysomyxa arctostaphyli Diet. Chrysomyxa emperti Schroet. ex Cumm. Chrysomyxa l ed i D By. Chrysomyxa ledicola Lagh. Chrysomyxa we i r r i i Jacks. Chrysomyxa woroninii Tranz. witches broom needle rust needle rust needle rust needle rust shoot rust 3 1 2 1 1 6 2 1 1 3 11 6 10 11 Coelomycetes Sphaeropsidales Dichomera gemmicola bud pathogen 1 Table VII - continued Forest Disease Number of Collections by Maturity Class! Class Order Genus/Species Comments 3 4 5 6 Hyphomycetes Stiqmina spp. 1 Stiqmina verrucosa (Morqan-Jones) needle spot 1 Sutton 1 Listed by FIDS age classes: 3(forest seedling); 4 (sapling); 5 (young growth); 6 (semi-mature). 2 Spruces of economic importance in central B r i t i sh Columbia include Picea glauca, Picea engelmannii and Picea glauca x engelmannii. 3 Based on col lect ions by FIDS Rangers between 1949 and 1982; 17,191 entries for age classes 3, 4, 5 and 6 for a l l species in Prince George Forest Region. Table VIII - Summary of descriptive s t a t i s t i c s 1 for immature stands* surveyed for pest occurrence and incidence in Supply Block "G" of the Prince George T.S.A. Stand (Plots) Tree Stems per Hectare Total Stems Total Spruce Healthy Spruce Damaged Spruce Stems per Hectare Weevil 4 Midge3 % of Total Spruce Weevil Midge 1 (7) 1071 (800-1440) 971 894 (620-1160) (540-1100) 77 (40-140) 8.2 (4.2-12.9) 2 807 670 628 (24) (214-1200) (214-1080) (214-1040) 3 (0-20) 39 (0-100) 0.5 (0-5.9) 5.9 (0-20.0) 3 (9) 644 617 536 (336-1180) (312-1100) (288-920) 49 (0-140) 31 (0-60) 6.9 (0-12.7) 4.4 (0-10.7) 4 (15) 719 579 553 (320-1040) (260-1040) (260-980) 20 (0-100) 7 (0-40) 3.5 (0-23.8) 1.3 (0-9.1) 5 820 327 287 (3) (700-880) (180-440) (100-440) 27 (0-40) 13 (0-40) 11.1 (0-22.2) 7.4 (0-22.2) 6 (16) 742 (0-1260) 736 (0-1260) 696 (0-1200) 12 (0-54) 28 (0-108) 1.4 (0-8.4) 3.7 (0-11.1) 7 491 415 413 (11) (200-1060) (200-760) (200-740) 2 (0-20) 0.2 (0-2.6) 8 (20) 563 (168-760) 455 (123-720) 421 (112-680) 16 (0-100) 18 (0-60) 2.9 (0-14.3) 4.1 (0-11.8) 9 (19) 876 811 677 (400-1420) (240-1040) (240-1040) 118 (0-360) 16 (0-100) 14.8 (0-30.8) 1.7 (0-9.1) Table VIII - continued Damaged Spruce 3 Tree Stems per Hectare Stand Stems per Hectare % of Total Spruce (Plots) Total Stems Total Spruce Healthy Spruce Weevil 4 Midge5 Weevil Midge 10 639 526 A86 18 22 4.2 2.8 (1A) (120-10A0) (60-1020) (60-1000) (0-60) (0-1A0) (0-20.0) (0-16.7) 11 92A 825 790 23 12 2.5 1.3 (13) (380-1200) (320-1120) (320-1020) (0-80) (0-60) (0-9.1) (0-6.A) 12 . A29 36A 328 36 0 9.1 0 (18) (20- 820)' (20-680) (20-680) (0-1AO) (0-53.8) 13 1015 780 76A 17 0 2.4 0 (23) (3A8-1660) (300-1580) (276-1580) (0-80) (0-9.0) 1A 597 A50 296 15A 0 30.8 0 (15) (160-1080) (100-8A0) (80-6A0) (20-700) (5.9-83.3) A l l 735 620 566 39 1A 6.6 2.2 (207) (0-1660) (0-1580) (0-1580) (0-700) (0-140) (0-83.3) (0-22.2) 1 Mean value and range (in parentheses). 2 Table III describes more fu l ly the stands examined. 3 Spruces of economic importance in central B r i t i sh Columbia include Picea glauca, Picea engelmannii and Picea glauca x engelmannii. 1 4 Pissodes strobl Peck (Coleoptera: Curculionidae). 5 Diptera: Cecidomyiidae, l ike ly spruce bud midge, Rhabdophaga swainel Fe l t . 52 Table IX - Summary of recordings of pests and other tree damaging agents in plantation surveys^. Damaging Agent Plots 2 with one or more occurrences Number Percent gall adelgid - attacking terminal 15 7.25 gall adelgid - heavy attack on branches 12 5.80 bud midge on terminal bud 71 34.30 Hylobius warreni 2 0.97 Dioryctria reniculelloides 2 0.97 Armillaria mellea 2 0.97 Pissodes strobi 110 53.14 animal browse 15 7.25 frost k i l l to terminal bud 12 5.80 mechanical damage - snow press, breakage 6 2.90 1 Table III describes the stands examined 2 A total of 207 0.05 hectare plots were established 53 Prlnct Gtorg* Each division on vertical axis - 10 % Figure 6- Occurrence of Pissodes s t r o b i and bud midge attack on immature i n t e r i o r spruce i n stands examined i n Supply Block *G' of the Prince George Timber Supply Area. 54 survey lines were given to the Prince George East Forest District for inclusion in their project files for the plantations examined. Daily survey production varied considerably depending upon terrain and brush cover on the plantation, distance between driving access and points-of-commencement and termination, and distance between plantations to be surveyed. The experienced production range was between 1500 and 6000 metres with an anticipated daily average of 4000 metres of five metre wide survey line being possible for experienced personnel. Although one person can satisfactorily complete the survey, a crew of two persons should be utilized for safety reasons. The analysis of data beyond the description statistics of the stands surveyed (Table VIII) and pest occurrences by plot (Table IX) would not be statistically valid due to the small size of data sets for each stratum. Ecological associations, plantation ages, planting stock types and provenances, site treatment methods and prevailing site conditions contributed to large variations in plantation performance and, possibly, pest incidence. Stratification with adequate sampling within each stratum is necessary to perform a detailed statistical analysis of pest occurrence in these interior spruce plantations. 4. DISCUSSION Field surveys of 14 immature spruce stands, comprised of 22 55 plantations established between 1963 and 1973, were completed during the summer and early autumn of 1983 (Table III; Table VIII; Table IX; fig 6). Two insect pests were found to occur consistently in the stands examined; Pissodes strobi attacked a mean of 6.6% of the total spruce stems and a bud midge (Diptera: Cecidomyiidae), likely Rhabdophaga swainei, had attacked a further 2.2% of the spruce component of the stands. A mean of 620 spruce stems per hectare, with 566 of these being categorized as healthy potential crop trees, was determined from the surveys to be the current stocking levels. These figures become significant when one considers the desired stand merchantable volume at rotation age. While there have been very few published investigations concerning the expected yield from the managed spruce plantations in the Province of British Columbia, Eis et al. (1982) concluded that managed, fully-stocked stands should produce greater volumes than are presently realized from the natural, unmanaged forests of the central interior of British Columbia. On Aralia sites, described as subhydric, permesotrophic with fair drainage, loam or clay soils, covering lower slopes, Eis et al. (1982) projected yields of 675 nfVha from 483 stems per hectare at a rotation age of 130 years. An anticipated yield at the proposed stand rotation age of 85 years can be projected at 290 m"5 per hectare from 490 spruce stems per hectare. The absence of merchantable spruce stems, either through site occupation by a non-preferred species or pest damage resulting in disposition, will result in reduced volume yields and decreased stand merchantability (Eis et al. 1982). Plantations, once established, must be managed to provide the greatest, highest quality volume of the preferred tree species. 56 Young plantation management and juvenile stand management, both being phases of total forest management, probably exert the greatest influences on stand merchantability of a l l silvicultural practices subsequent to stand establishment. Site preparation prior to planting, type and condition of planting stock, and planting methods largely determine the success of a spruce plantation in achieving a 1free-to-grow1 status (Dobbs 1972; McMinn 1979). Forest insect pests probably show their greatest influence on stand profiles from that stage, generally achieved by age 10, to age 35, by deforming, predisposing or even killing potential crop trees. After age 35, i t is expected that forest diseases will begin to affect stand merchantability through growth reduction, volume reduction and tree mortality, caused primarily by the root rot fungi (Whitney 1976). Pest control techniques strategically applied are needed to maintain stand merchantability and value. There are, however, two pre-requisites to the pest-control policy decision: 1- there must be a reliable estimate of the losses attributable to the pest; and, 2- there must be a reliable estimate of the impact of these current losses upon future merchantability of the stand. Reliable loss estimates attributable to any particular pest can be related to the type of damage done by the pest and the incidence of the pest as determined by surveys. A survey of similar format to that conducted during the course of this project will assemble data to provide a stand overview. However, such a technique cannot be used to provide 57 sufficient data from which pest control decisions or plans may be drawn or formulated. It can be used to identify where more detailed and pest-specific surveys are needed from which confident decisions or plans may be developed. The degree of infestation at which the 'decision survey' is initiated can only be determined by studies directed toward that purpose and after control threshold infestation levels for particular pests have been established. Stand composition, stocking levels, dynamics and age must be related to past and current pest levels by the forest manager before making that critical decision. It is difficult to calculate the impact of current losses. To determine impact, one must have estimates of: 1- the desired final crop based on stand management goals and guidelines; and, 2- the effect of tree damage or mortality at any particular age upon the final crop merchantability. Both parameters are difficult to define since, in British Columbia, there are no firm stand management goals or guidelines for interior spruce at this time, and the oldest managed immature spruce stands in the central interior of British Columbia are currently at ages less than 25% of the anticipated rotation age. Some projections, however, can be made to support the concept under discussion. It has been estimated that 13 624 3 m /yr is lost in increment for a l l merchantable species to pests active in immature stands in the Prince George T.S.A. (Anon. 1984b). Projected yields of managed spruce stands have been developed and discussed by several authors (Stiell and Berry 1973; Stiell 1976; 58 Revel 1981; Eis et al. 1982). An anticipated stand profile (Fig. 7) was developed to assist in stand management decision-making. Factors considered included: known values for planting densities; early survival and juvenile growth with projected, possibly theoretical, values for height; mortality due to between-tree competition; and, volume production in the latter stages of stand development. In the absence of any other spruce stand projections this profile will be followed for this discussion. Once a spruce plantation has become satisfactorily established and declared 'free-to-grow1 i t must be scheduled to undergo formal pest detection surveys. Experience from this project suggested that overview surveys need not be scheduled earlier than ten years and should occur no later than 15 years from the date of plantation establishment. The exact timing will be determined by the forest manager and should depend upon the general state of the crop trees as well as historical and current pest incidence for the particular area. Early detection and identification of the problem greatly enhances the possibility of control measures being successful. Equally, i f not more important, is the realization that even the most effective controls may be rendered useless i f the detection of the problem is unduly delayed. Sampled pest incidence and intensity data coupled with the number of remaining potential crop spruce trees can be compared to the stand stocking profile to assist the forest manager in making the pest management policy decision. The management objective for immature stands should be to maintain their stocking level above the projected value for any particular stand age. In this manner, in a single thinning operation, F i g u r e 7- P r o j e c t e d performance o f i n t e r i o r spruce on A r a l i a s i t e s i n the c e n t r a l i n t e r i o r o f B r i t i s h Columbia. Developed from d a t a from: S t i e l l and B e r r y 1973; S t i e l l 1976; Revel 1981; E i s e t a l . 1982. 60 the forest manager has the opportunity to choose the best potential crop trees rather than being forced to accept, or save, the trees not attacked by the forest pests as the future merchantable crop. Stocking data derived from plantation surveys (Table VIII) can be compared to projected stand performance (Fig. 8) to assist in the determination of stand management practices to be pursued. The comparison shows three primary zones and subsequent causes of action: 1- stands where the stocking by healthy trees is greater than the projected performance, thereby allowing stand management practices selecting potential crop trees on the basis of form, rate of growth or between-tree competition; 2- stands where the stocking by healthy trees is less than the projected performance yet greater than the desired stocking at harvest, resulting in stand management activities directed towards the maintenance of a l l existing healthy trees; and, 3- stands where the stocking by healthy trees is less than the desired stocking at harvest, thus requiring stand management policy decisions which may range from the acceptance of a reduced volume at harvest to total stand rehabilitation and replanting. Many of the stands surveyed were supporting damaging populations of Pissodes strobi at the time of assessment (Table VIII). Examination revealed that most of these infestations had only been active for a maximum of five years and that, in many locations, the infection centres appeared to be expanding at an increasing rate in the more recent years. While having a damage mean of only 6.6% of the total planted spruce 1400, ISOO. 1000. % V. o soo. $ • • 600-> 4 to c 1 400 • .12 .3 .14 200 Q O tO 20 SO STAND AGE (years from *stobfi$hm9tit) i LEGEND — — Projected Stocking (Fig. 7) Stocking at Harveet (ISO yrt ) ^ Stand Identification ( Tool* III) F i g u r e 8 - Number o f h e a l t h y p l a n t e d i n t e r i o r spruce t r e e s p e r hec t a r e by s t a n d age f o r stands surveyed i n Supply B l o c k 'G' o f the P r i n c e George Timber Supply Area compared t o p r o j e c t e d performance on A r a l i a s i t e s i n the c e n t r a l i n t e r i o r o f B r i t i s h Columbia. 62 trees, a figure considered by many people to be almost insignificant, experiences elsewhere in this Province (Wood et al. 1984) and in eastern Canada (Sterner and Davidson 1983) demonstrate that forest managers must be acting now to maintain a healthy stand and keep a maximum of stand management options open. The survey and assessment approach described in this report will work well for forest pests which are endemic in the immature forests and increase to epidemic proportions over a period of a few years. An insect which typically follows this pattern is Pissodes strobi, which appears to be the most significant threat to the well-being of the spruce plantations of the Prince George T.S.A. at this time (Cozens 1983; Erickson and Loranger 1984). This insect can build rapidly in numbers over a period of years but can be detected easily prior to its reaching epidemic proportions. Opportunities exist throughout the development of a forest stand to control P. strobi, directly through leader clipping and brood removal, or indirectly through silvicultural manipulation (Cozens 1983). Rhabadophaga swainei, while generally being considered an unimportant.forest pest in eastern Canada (Blais 1960; Lindquist and McNamee 1960), may become economically more important in western Canada (Cerezke 1972). The incidence and dynamics of this insect make i t also possible to detect by the survey procedure utilized. Insects whose populations erupt as 'instant' outbreaks, namely the defoliators, would not likely be detected by such a survey method which would be conducted every ten years or so. These insects will only be detected through continuous stand monitoring by forest workers 63 in the course of their daily schedules or from surveys initiated as a result of pest-specific requirements. While many defoliators may be of potential concern (Table IV; Table V), Erickson and Loranger (1984) considered only Pikonema alaskensis of importance and described i t as occasionally becoming epidemic in dense plantations of young spruce. Morse and Kulman (1984) observed that P. alaskensis was responsible for 25% of the mortality in a white spruce plantation five years after planting in Minnesota. The pest-control decision for defoliators should follow a logic similar to that previously discussed, weighing pest damage, stand dynamics and final crop merchantability to result in a rational decision. While not included in the topic of this thesis, some comment must be made regarding the projected stand profile (Fig. 7) and the stand rotation ages chosen by the forest managers, ie.- the British Columbia Forest Service. To harvest a spruce stand at an age of 85 years is to remove the trees when they are at their prime and growing volume at almost the greatest annual rate in their lives. In absolute values, to harvest at 85 years yields a volume of 290 m"5 per hectare; to harvest at 130 years yields a volume of 675 nv5 per hectare. By delaying harvest by only 15 years, to age 100, a resultant increase of 50% in volume per hectare may occur. This additional volume, as a result of crown closure and branching habit of interior spruce, will be 'quality' volume which will yield high quality veneer or clear lumber. In terms of stand growth, at age 85 the mean annual increment (MAI) is 3.41 m"5 per hectare per year; at age 130 the MAI is 5.19 m5 per hectare per year. 64 This 52% increase in volume growth should significantly influence annual allowable cut determinations in Timber Supply Areas in this Province. If the indications are correct — and there is no reason to doubt them i f high yield silviculture is practiced to its fullest — the present iJoncept of rotation age determination should be re-examined and changed. Spruce can be successfully regenerated after harvesting in the Prince George T.S.A. and grown to a merchantable crop of a volume per hectare at least equal to that of the naturally-occurring unmanaged stands. The key elements of such an endeavour are: - complete and effective site preparation after harvesting and prior to planting - planting with healthy spruce seedlings of the correct stock type at a density of at least 1200 stems per hectare - plantation monitoring for brush, or other pest incursion, and control decisions - pest management operations as required - crop tree selection and thinning to approximate final crop spacing of 500 stems per hectare at age 35 - fertilizer application when and i f determined to be necessary - continued stand monitoring (Fig. 9) and protection/silvicultural manipulation as necessary A forest in which established forestry practices are applied by professional forest managers will result in maximum merchantable yield at rotation. FOREST PHASE Mature Harvest Plantation Young Immature Older Immature Merchantable STAND AGE (years) O to 40 SO SO IOO STAND ENTRIES Pre-harvest Harvest Plantation Pest Pest and Assessment and Survival Survey Pre-ttilnnlng Reforest Assessment Thinning General Pest and Stand Performance Assessments Pro-harvest Assessment PESTS of CONCERN Spruce beetle. Brush, Root rot Cutworms Spruce weevil. Bud midge, Root ret Spruce weevil, Defoliators, Root rot Spruce beetle, Root rot F i g u r e 9 - Routine stand survey and monitoring e n t r i e s necessary i n the development o f a merchantable i n t e r i o r spruce f o r e s t . 66 5. CONCLUSIONS The major findings resulting from this study of pests of immature spruce stands in the Prince George Timber Supply Area are: 1- Two insects, Pissodes strobi and a gall midge, likely Rhabdophaga  swainei, were found to be present in most stands surveyed in sufficient numbers and to be causing significant economic damage to be considered pests of immature spruce stands in the Prince George T.S.A. 2 - Detection of pests in the immature spruce stands is not, at present, at a level that provides data suitable for making informed pest management decisions. 3- Forest diseases were not considered to be significant pests in the stands at the time surveyed, but are expected to become influences in stand development and merchantability after age 35. 4- Two forms of pest survey are required in the management of young stands; a general stand/pest overview and, where necessary, a pest-specific control decision survey, which is yet to be developed. 5- There is an absence of definite management strategies for the management of regenerated interior spruce forests in the Province of British Columbia. While i t is realized that pests - both insect and disease - are responsible for serious losses, they cannot be effectively managed to reduce these losses without stand management goals and guidelines. 6- Establishment of a new forest by planting must ensure that a 67 minimum of 1200 healthy seedlings are planted per hectare to give forest managers some 'allowance' within which to exercise their professional options throughout the stand development. 7- The present concept of rotation age determination appears to be minimizing the long-term stand yields to meet the short-term social objectives. These findings indicate that the genuine management of immature spruce stands may be lacking in some respects. Without established policies and goals there cannot be direction to the management efforts. The forest industry, which in this context includes the government agencies, is extremely naive i f i t believes that a merchantable forest crop will be realized from a management regime where a forest is planted only to be virtually ignored until the time of harvest. To ensure ful l return on the investment in the immature forests, constant monitoring and stand management must be judiciously applied by forest managers (Fig. 9). No single management activity can be considered in isolation from other possibilities. Each has its effect upon the stand and this effect is modified by the effects of other treatments. Forest management must include a l l aspects of tree growth, pest influences, silvicultural practices and stand manipulation applied in a co-ordinated effort to maximize the merchantable harvest at the optimum rotation age. 6. RECOMMENDATIONS Based on the results of this study, the following 68 recommendations are proposed: 1- Guidelines for the management of immature interior spruce stands to rotation age be developed on a Provincial basis and instituted at the district level to ensure, through proper forest management techniques, the greatest volume of the highest quality product from each hectare of forest land at the optimum rotation age. 2- Projected managed interior spruce stand yield tables be developed and fully considered in the determination of stand rotation ages to ensure that the f u l l productivity of each site is achieved. 3- Studies be commenced on the biology, action and management of Pissodes strobi, Rhabdophaqa swainei and likely other pests in the immature spruce forests of the Prince George Timber Supply Area. 4- Periodic plantation/immature stand monitoring surveys be conducted and include a l l elements of stand dynamics - tree growth, insect and disease activity, brush and deciduous competition, etc. - to arrive at a total stand treatment prescription. 5- Pest-specific control decision surveys be developed and instituted for each pest as they begin to have significant impact on the immature interior spruce forests. 6- Studies be initiated on the forest disease factors active in immature stands of interior spruce so that forest managers will be aware of the potential impact of these agents upon stand development and merchantability. 69 REFERENCES Anonymous. 1966. Native Trees of Canada. Can. Dept. For. and Rural Dev. Bui. No. 61. 6th Ed. 291 pp. Anonymous. 1978. Volume age curve index - Forest Inventory Zone I. Prov. B.C. Min. For. Inventory Branch. Anonymous. 1979. Prince George Timber Supply Area yield analysis report. Prov. B.C. B.C. For. Serv. Planning Br. 55 pp. Anonymous. 1980. Forest and range resource analysis technical report. Prov. B.C. Min. For. 802 pp. Anonymous. 1982. Prince George T.S.A. summary plan. Prov. B.C. B.C. For. Serv. Prince George Forest Region. 55 pp. Anonymous. 1983. Summary of pest reports for Prince George Forest Region; age classes 3-6. Can. For. Serv. Forest Insect and Disease Survey. Victoria, B.C. Anonymous. 1984a. Site history record summaries. Prov. B.C. B.C. For. Serv. Prince George Forest Region. Anonymous. 1984b. Timber Supply Area pest management summaries. Prov. B.C. B.C. For. Serv. Prince George Forest Region. Baranyay, J.A. and W.G. Ziller. 1972. Broom rusts of conifers in British Columbia. Can. For. Serv. PFRC FPL #48. 6 pp. Bernsohn, K. 1980. Cutting Up the North. Hancock House Publishers Ltd. North Vancouver. 192 pp. Blais, J.R. 1960. Observations on Rhabdophaga swaineii Felt in the Gaspe Peninsula. Can. Dept. Agric. Bi-Mon. Prog. Rep. 16(1):3. Boyce, J.S. 1961. Forest Pathology. 3rd Ed. McGraw-Hill Book Company. Toronto. 572 pp. Cayford, J.H. and A. Bickerstaff. 1968. Man-made forests in Canada. Dept. Fish, and For. For. Br. Publ. No. 1240. 68 pp. Cerezke, H.F. 1972. Observations on the distribution of the spruce bud midge (Rhabdophaga swaineii Felt) in black and white spruce crowns and its effect on height growth. Can. J. For. Res. 2:69-72. Cozens, R.D. 1983. The spruce weevil, Pissodes strobi Peck (Coleoptera: Curculionidae) A review of its biology, damage and control techniques with reference to the Prince George Timber Supply Area. B.C. Min. For. Prince George Forest Region. F.S. Int. Rep. PM-PG-3. 71 pp. 70 Dobbs, R.C. 1972. Regeneration of white and Engelmann spruce. Can. For Serv. PFRC Info. Rep. BC-X-69. 77 pp. Draper, D. 1983. An assessment of plantation performance data in the Prince George Forest Region. B.C. Min. For. Res. Br. E.P. 938. 33 pp. Eis, S., D. Craigdallie and C. Simmons. 1982. Growth of lodgepole pine and white spruce in the central interior of British Columbia. Can. J. For. Res. 12:567-75. Erickson, R.D. and J.F. Loranger. 1984. History of population fluctuations of important forest insects in the Prince George Forest Region 1942-1982. Can. For. Serv. PFRC. 60 pp. Foster, R.E. and G.W. Wallis. 1969. Common tree diseases of British Columbia. Dept. Fish and For. For. Br. Publ. No. 1245. 116 pp. Fowells, H.A. 1965. Silvics of Forest Trees of the United States. USDA For. Serv. Agric. Handbook No. 271. 762 pp. Fox, D.J. and K.E. Guire, 1976. Documentation for MIDAS (Michigan Interactive Data Analysis System), 3rd Ed. Statistical Research Laboratory, University of Michigan. 203 pp. Fraser, A.R. and J.L. Alexander. 1949. The development of the spruce-balsam type in the Aleza Lake Experimental Forest. B.C. For. Serv. Tech. Publ. T.32. 41 pp. Funk, A. 1978. Canker diseases of spruce. Can. For Serv. PFRC FPL #65. 4 pp. Furniss, R.L. and V.M. Carolin. 1977. Western Forest Insects. USDA For. Serv. Misc. Publ. 1339. 651 pp. Garman, E.H. 1957. The occurrence of spruce in the interior of British Columbia. Dept. Lands and For. B.C. For. Serv. Tech. Publ. T.49. 31 pp. Harlow, W.M., E.S. Harrar and F.M. White. 1979. Textbook of Dendrology. McGraw-Hill Book Company. New York. 510 pp. Holsten, R.H., R.A. Werner and T.H. Laurent. 1980. Insects and Diseases of Alaskan forests. USDA For. Serv. Alaska Region Report No. 75. 187 pp. Krajina, V.J., K. Klinka and J. Worrall. 1982. Distribution and Ecological Characteristics of Trees and Shrubs in British Columbia. The University of British Columbia, Faculty of Forestry. 131 pp. Lees, J.C. 1966. Release of white spruce from aspen competition in Alberta. Can. Dept. For. Publ. No. 1163. 16 pp. Lindquist, O.H. and D.M. McNamee. 1960. The spruce bud midge in Ontario. Can. Dept. Agric. Bi-Mon. Prog. Rep. 16(1):3. 71 McMinn, R.G. 1979. Site preparation for planting: Needs and opportunities in moist spruce/alpine f i r ecosystems in north central British Columbia. Paper presented to Sumposium "Soils, Forest Growth and Management". Can. Soc. of Soil Science. Fredericton, N.B. 11 pp. Morrison, D.J. 1976. Armillaria root rot. Can. For. Serv. PFRC FPL #35. 5 pp. Morrison, D.J. 1981. Armillaria root rot - a guide to disease diagnosis, development and management in British Columbia. Can. For. Serv. PFRC BC-X-203. 15 pp. Morse, B.W. and H.M. Kulman. 1984. Plantation white spruce mortality: estimates based on aerial photography and analysis using a l i f e table format. Can. J. For. Res. 14:195-200. Nienstaedt, H. 1957. Silvical characteristics of white spruce (Picea  glauca). USDA For. Serv. LFES. Stn. Paper No. 55. 23 pp. Revel, W.J. 1981. 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Development of unthinned white spruce plantations to age 50 at Petawawa Forest Experiment Station. Can. For. Serv. Publ. No. 1317. 18 pp. Sutton, R.F. 1969. Silvics of white spruce (Picea glauca (Moench) Voss). Dept. Fish, and For. For. Br. Publ. No. 1250. 57 pp. Unger, L.S. 1972. Common needle diseases of spruce in British Columbia. Can. For. Serv. PFRC FPL #39. 7 pp. 72 Walsh, S.J. 1980a. Height growth of spruce, pine and f i r plantations in the Prince George Forest Region. Part 1: Ranger District 15. 26 pp. Walsh, S.J. 1980b. Height growth of spruce, pine and f i r plantations in the Prince George Forest Region. Part 3: Willow and Purden PSYU's, Prince George East District. 33 pp. Whitney, R.D. 1972. Root rot in white spruce planted in areas formerly heavily attacked by Polyporus tomentosus in Saskatchewan. Can. For. Serv. Bi-Mon. Res. Notes. 28(4):24. Whitney, R.D. 1976. Root rot of spruce and balsam f i r in northwestern Ontario. I. Damage and implications for forest management. Can. For. Serv. Rep. O-X-241. 49 pp. Whitney, R.D. 1977. Polyporus tomentosus root rot of conifers. Can. For. Serv. Great Lakes For. Res. Centre. For Tech. Rep. No. 18. 11 pp. Wood, C.S., G.A. Van Sickle and T.L. Shore. 1984. Forest insect and disease conditions. British Columbia & Yukon 1983. Can. For. Serv. Infor. Rep. No. BC-X-246. 27 pp. 73 APPENDIX I Spruce Plantation Pest Field Survey Recording Form 74 75 APPENDIX II Spruce Plantation Pest Summary Form SPRUCE PLANTATION PEST SURVEY PLANTATION NUMBER 'i'hH^'O^ LOCATION rOpR-TH T'ut&beM DATE PLANTED '9*72- SURVEYED AND SUMMARIZED B V O f e ^ O STRIP LENGTH t£(aO_ m STRIP WIDTH m PLANTATION AREA Ha CS>prua\ SAMPLING INTENSITY PERCENT STRIP INTERVAL HEALTHY SPRUCE DAMAGED SPRUCE OTHER TREE SPECIES TOTALS PISSODES STROBI GALL APHID (TERMINAL) GALL APHID (BRANCH) CECIDOMYID HYLOBIUS WARRENI ANIMAL BROWSE MECHANICAL OTHER seoie O - l o O 2-> ACO 2. CO AO "S to IS sto lOO -VOO }•> fctO V Co> 40 I to 2. AO *i8o zoo -50G •8 J(.o > cO 10 I 2.0 2X) Hoo ZXJ A.0O 1 Co) l o t2.o •HOO-aOO 1 t o 1 ZO z.\ A2Q i"oo - tot) 7 (•>'!> IAO 1 e^> 3 to 2. AO S~°> H80 &OO -*JOO A; C»> BO 7- HO > to l o o - 8 « > >fc mo 4 0 ) 80 1 ro 1 to 86O 1 o> I. A 2- I f _ paUO^ b"" ( ; * A 4»aTO+vK- Mare: l « W - « « « U - - pUf 77 APPENDIX III Sample Aerial Photograph (1:20 000 scale) showing survey lines for assessment of pests in young interior spruce stands in Supply Block 'G' of the Prince George Timber Supply Area 78 

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