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The Effects of Fertilizer Treatments on the Resin Canal Defenses of Spruce and Incidence of Attack by the White Pine Weevil, Pissodes Strobi

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The Effects of Fertilizer Treatments on the Resin Canal Defenses of Spruce and Incidence of Attack by the White Pine Weevil, Pissodes Strobi THE EFFECTS OF FERTILIZER TREATMENTS ON THE RESIN CANAL DEFENSES OF SPRUCE AND INCIDENCE OF ATTACK BY THE WHITE PINE WEEVIL, PISSODES STROBI. by Lara vanAkker B.Sc, University of Victoria, Victoria, British Columbia, 1996 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Faculty of Forestry) (Department of Forest Science) We accept this thesis as conforming to the required standard UNIVERSITY OF BRITISH COLUMBIA 2002 © Lara vanAkker, 2002 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, 1 agree that the Library shall make it freely available for reference and study. 1 further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of fb^t SUSAC£ The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT The white pine weevil, Pissodes strobi (Peck), is a serious pest of regenerating spruce (P/'cea spp.) in British Columbia. On the coast, damage by this weevil results in such severe stem defects and growth losses in Sitka spruce (Picea sitchensis), that planting this species is not currently recommended in high weevil hazard areas. In the interior of the province, hundreds of millions of interior spruce seedlings (P/'cea glauca x englemanii) are currently in weevil susceptible age classes. Past attempts to control this weevil have been unsuccessful. Current research is focused on identifying trees with genetic resistance to the weevil and identifying the defense traits which give rise to this resistance. While weevil resistance has been shown to be heritable, environmental factors such as plant nutrient status may alter the expression of defense traits. My goal was to determine the effects of fertilization treatments on the resin canal defenses in spruce and incidence of weevil attack. Fertilizer effects on tree size variables were measured to provide baselines for the comparison of treatment groups and to facilitate discussion on the effects of variation in tree size due to fertilizer treatment, on incidence of weevil attack. The constitutive resin canal systems of Sitka and interior spruce maintained under several fertilizer regimes were compared by histological examination of leader cross sections. Traumatic response intensity was compared utilizing mechanical wounding to stimulate a traumatic response, followed by histological examination of cross sections through the wounded stem. Incidence of weevil attack in response to fertilizer treatments was studied in a caging experiment in which weevils were given a choice between trees from different fertilizer treatments, and in a variably fertilized plantation, naturally infested with weevils. The effects of fertilization on constitutive resin canal variables were influenced by spruce genotype, but not resistance status. In general, there was a dilution in cortical resin canal defenses in response to fertilization, which included a decrease in resin canal density and an increase in depth and distance between inner resin canals. These effects corresponded with, and may have been due to increasing bark thickness in response to fertilization. In severely nutrient stressed trees, fertilization may also improve the ability of trees to produce a traumatic response. Fertilization increased the incidence of weevil attack in both Sitka and interior spruce. In interior spruce, more than twice as many trees were attacked in the intense fertilizer treatments than in the unfertilized control groups. The observed increase in weevil attack in the more intense fertilizer treatments may be attributed to increased host vigor, resulting in an increase in resources available for weevil feeding and oviposition and a dilution of cortical resin canals. It is recommended that further studies be undertaken to investigate the effects of fertilization on other factors such as resin composition and flow. ii N TABLE OF CONTENTS ABSTRACT ii LIST OF TABLES vi LIST OF FIGURES viii ACKNOWLEDGEMENTS xi GENERAL INTRODUCTION 1 Spruce and Pissodes strobi (Peck) 1 Life history of the white pine weevil 2 Controlling weevil damage 4 Spruce resistance to the weevil 5 Plant defenses and resistance mechanisms 7 Fertilization, herbivores and plant defenses 12 FACTORS THAT INFLUENCE WEEVIL ATTACK RATES 17 Tree size 18 Constitutive resin canal defenses 19 Traumatic resin canal defenses 25 TRIAL 1. FERTILIZER EFFECTS ON INCIDENCE OF WEEVIL ATTACK AND RESIN CANAL DEFENSES IN SUSCEPTIBLE SPRUCE FAMILIES 30 METHODS 30 Tree material and fertilization 30 Data collection and analysis 32 Tree size 32 Constitutive resin canal characteristics 33 Traumatic resin canal defenses 35 Incidence of weevil attack 36 RESULTS AND DISCUSSION 37 Tree size 37 Constitutive resin canal defenses 40 Traumatic resin canal defenses 43 Incidence of weevil attack .47 CONCLUSIONS 50 TRIAL 2. FERTILIZER EFFECTS ON CONSTITUTIVE RESIN CANAL DEFENSES IN RESISTANT AND SUSCEPTIBLE SPRUCE GENOTYPES 51 METHODS 51 Tree material and fertilization 51 iii Data collection and analysis 52 Tree size 52 Constitutive resin canal defenses 53 RESULTS AND DISCUSSION 53 Tree size 53 Constitutive resin canal defenses 57 CONCLUSIONS 68 TRIAL 3. FERTILIZER EFFECTS ON INCIDENCE OF WEEVIL ATTACK AND RESIN CANAL DEFENSES OF INTERIOR SPRUCE OF UNKNOWN RESISTANCE STATUS 69 METHODS 69 Tree material and fertilization 69 Data collection and analysis 71 Tree size 71 Constitutive resin canal defenses 71 Traumatic resin canal defenses 72 Incidence of weevil attack 72 RESULTS AND DISCUSSION 73 Tree size 73 Constitutive resin canal defenses 76 Traumatic resin canal defenses 81 Incidence of weevil attack 82 CONCLUSIONS 84 SUMMARY AND DISCUSSION 85 Constitutive resin canal defenses 85 Traumatic resin canal defenses 90 Incidence of weevil attack 91 CONCLUSIONS 93 LITERATURE CITED 96 APPENDICES 110 Appendix 1. Statistical model for the analysis of fertilizer and family effects on tree size variables and constitutive and traumatic resin canal defenses in Sitka spruce seedlings, Trial 1 111 Appendix 2. Recipe for formalin acetic acid (FAA) 111 Appendix 3. Formulae for the calculation of constitutive resin canal variables: SZIN, SZOUT, AOCC, NMMS, DEP, GAP and BTHK 111 Appendix 4. Traumatic response rating system as used by Brescia (2000) 112 iv Appendix 5. Statistical model for the analysis of fertilizer, resistance class and genotype effects on constitutive resin canal variables in Sitka spruce somatic seedlings, Trial 2 112 Appendix 6. Statistical model for the analysis of fertilizer and replicate effects on constitutive and traumatic resin canal variables in interior spruce, Trial 3 113 V LIST OF TABLES Table Page 1 Abbreviation, description and unit of each constitutive resin canal characteristic measured to determine the effects of fertilization on spruce defenses 24 2 Origins of Sitka spruce parent trees for seedlings used in Trial 1 31 3 NPK fertilizer (Osmocote®, 8-9 month slow release formulation) applied to 1 year-old Sitka spruce seedlings in 1 gallon pots, in each of four treatments in a study of fertilization effects on spruce defenses. Treatments were applied in April 1998 32 4 Average height of 1 year-old potted Sitka spruce seedlings from eight weevil susceptible families at the start of Trial 1 (n=60 for each group) 37 5 Results of analysis of variance to determine the effects of four levels (0, 7, 16, 25 g) of NPK fertilizer (Osmocote®, 8-9 month slow release formulation) on constitutive resin canal variables of 2 year-old potted Sitka spruce seedlings 41 6 Average constitutive resin canal characteristics observed in quarter cross sections of leaders from 2 year-old potted Sitka spruce maintained under four levels (0, 7, 16, 25 g) of NPK fertilizer (Osmocote®, 8-9 month slow release formulation) 42 7 Summary of ANOVA to detect the effects of fertilization (FERT) and family (FAM) on traumatic response rating of 3 year-old potted Sitka spruce mechanically wounded to simulate weevil feeding and fertilized with three levels (0, 7, 25 gr) of NPK fertilizer (Osmocote®, 8-9 month slow release formulation) 46 8 Means and standard deviations (SD) of traumatic response rating, on a scale from 0-6, in 3 year-old potted Sitka spruce fertilized with three levels (0, 7, 25 g) of NPK fertilizer (Osmocote®, 8-9 month slow release formulation). Values with the same letter are not significantly different according to Tukey's HSD (p<.05) 46 9 Mean number and range of Pissodes strobi oviposition punctures and number of Sitka spruce trees with oviposition, failed and successful attacks and brood emergence, in three NPK fertilizer treatments (Osmocote®, 8-9 month slow release formulation, 0, 7, 25 g) (FERT) (n=18 trees for each group) 47 10 Identification, origin and resistance status of parent trees for Sitka spruce somatic seedlings used in Trial 2 51 VI 11 NPK fertilizer (Osmocote®, 8-9 month slow release formulation) applied to 1 year-old Sitka spruce somatic seedlings in 1 gallon pots, in each of four treatments, in a study of fertilization effects on spruce defenses. Treatments were applied in May 1999 52 12 Height (cm) prior to fertilization, of 1 year-old Sitka spruce somatic seedling from weevil resistant (R) and susceptible (S) genotypes 54 13 Results of ANOVA to detect
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