Pissodes Strobi Peck Research Articles

Cuticular Hydrocarbon Recognition in the Mating Behavior of Two Pissodes Species.

Two sibling weevil species, Pissodes strobi Peck and P. nemorensis Germar (Coleoptera: Curculionidae), can form reduced-fitness hybrids in the laboratory, but neither their premating isolation mechanisms nor mating behaviors are well-understood. Cuticular hydrocarbons (CHCs) have been reported as crucial chemical cues in mating recognition in many insects, including weevils, and, thus, may also mediate the mating behavior of P. strobi and P. nemorensis. We conducted a series of behavioral observations, bioassays, and chemical analyses to investigate the role of CHCs in their mating behavior. Copulation behavior of both species followed similar steps: approaching, mounting, tapping, aedeagus extrusion, and copulation. In P. strobi, hexane extraction significantly reduced the number of successful male copulations compared with freeze-killed females. Conversely, significantly fewer P. nemorensis males copulated with dead females compared with live females. No significant differences were detected among hexane-extracted, freeze-killed or recoated female carcasses to P. nemorensis. These findings suggested that female cuticular extracts contain important cues in mate recognition in P. strobi but not in P. nemorensis. We identified 21 CHCs from both species with variation in abundances between sexes and seasons. Discriminant analysis revealed incomplete overlap of CHC compositions in females of the two species in summer, when hybridization potentially occurs.

Multi-trait genomic selection for weevil resistance, growth, and wood quality in Norway spruce.

Plantation‐grown trees have to cope with an increasing pressure of pest and disease in the context of climate change, and breeding approaches using genomics may offer efficient and flexible tools to face this pressure. In the present study, we targeted genetic improvement of resistance of an introduced conifer species in Canada, Norway spruce (Picea abies (L.) Karst.), to the native white pine weevil (Pissodes strobi Peck). We developed single‐ and multi‐trait genomic selection (GS) models and selection indices considering the relationships between weevil resistance, intrinsic wood quality, and growth traits. Weevil resistance, acoustic velocity as a proxy for mechanical wood stiffness, and average wood density showed moderate‐to‐high heritability and low genotype‐by‐environment interactions. Weevil resistance was genetically positively correlated with tree height, height‐to‐diameter at breast height (DBH) ratio, and acoustic velocity. The accuracy of the different GS models tested (GBLUP, threshold GBLUP, Bayesian ridge regression, BayesCπ) was high and did not differ among each other. Multi‐trait models performed similarly as single‐trait models when all trees were phenotyped. However, when weevil attack data were not available for all trees, weevil resistance was more accurately predicted by integrating genetically correlated growth traits into multi‐trait GS models. A GS index that corresponded to the breeders’ priorities achieved near maximum gains for weevil resistance, acoustic velocity, and height growth, but a small decrease for DBH. The results of this study indicate that it is possible to breed for high‐quality, weevil‐resistant Norway spruce reforestation stock with high accuracy achieved from single‐trait or multi‐trait GS.

Optimum Vegetation Conditions for Successful Establishment of Planted Eastern White Pine (Pinus strobus L.)

The 10th-growing season performance of planted eastern white pine (Pinus strobus L.) seedlings was evaluated in response to herbaceous and woody vegetation control treatments within a clearcut and two variants of the uniform shelterwood regeneration system (single vs. multiple future removal cuts). Herbaceous vegetation control involved the suppression of grasses, forbs, ferns and low shrubs for the first 2 or 4 growing seasons after planting. Deciduous woody vegetation control treatments, conducted in combination with the herbaceous treatments within a response-surface design, involved the permanent removal of all tall shrubs and deciduous trees at the time of planting, at the end of the 2nd or 5th growing seasons, or not at all. In general, the average size of planted pine was related positively to the duration of herbaceous vegetation control and negatively to delays in woody control. White pine weevil (Pissodes strobi Peck) altered these trends, reducing the height of pine on plots with little or no overtopping deciduous woody vegetation or mature tree cover. Where natural pine regeneration occurred on these plots, growth was similar but subordinate to the planted pine. Data from the three sites indicate that at least 60% of planted pine may be expected to reach an age-10 height target of 2.5 m when overtopping cover (residual overstory + regenerating deciduous) is managed at approximately 65% ± 10%, and total herbaceous cover is suppressed to levels not exceeding 50% in the first five years. On productive sites, this combination may be difficult to achieve in a clearcut, and requires fairly rigorous vegetation management in shelterwood regeneration systems. Currently, synthetic herbicides offer the only affordable and effective means of achieving such vegetation control.

High genetic variation and moderate to high values for genetic parameters of Picea abies resistance to Pissodes strobi

Genetic parameters of Picea abies resistance to the white pine weevil (Pissodes strobi Peck) were estimated from 193 full-sib and 166 half-sib families in six 10-year-old progeny trials. The estimated family and individual heritability values for the cumulative weevil attack rate between ages 6 and 10 (CWA6–10) were high and moderate for both full-sib families (0.61 and 0.28, respectively) and half-sib families (0.85 and 0.40, respectively), indicating strong genetic control for this trait in Norway spruce. The fact that specific combining ability (SCA) variance represents 35 % of the general combining ability (GCA) variance suggests that non-additive (dominant) effects are weak. The strong type B correlations found for CWA6–10 (\( {\widehat{r}}_{\mathrm{B}}=0.96 \) for full-sib families and \( {\widehat{r}}_{\mathrm{B}}=0.81 \) for half-sib families) indicate that family ranks were stable across sites. For three of the five sites with high attack levels, genetic correlations were not significant between CWA6–10 and tree height at age 5. Moderate positive genetic correlations were detected between CWA6–10 and tree diameter at age 10 (\( {\widehat{r}}_{\mathrm{A}} \) from 0.29 to 0.60), but specific families showing both high resistance and good diameter growth can be found. These results suggest that the genetic improvement of Norway spruce for resistance to white pine weevil can be achieved successfully without adversely affecting growth.

White pine (Pinus strobus L.) regeneration dynamics at the species’ northern limit of continuous distribution

The abundance of eastern white pine (Pinus strobus L.) has been significantly reduced across its distribution range over the past few centuries. The species’ regeneration dynamics is well documented in the centre of its range, but is poorly understood at the northern limit of continuous distribution. To address this knowledge gap, we quantified natural white pine regeneration in unmanaged mature stands, identified the most important variables influencing it, and evaluated the impact of damaging agents, namely white pine blister rust (Cronartium ribicola J.C. Fisch.), white pine weevil (Pissodes strobi Peck), and herbivory. We also quantified the influence of remnant stands and residual trees on the spatial distribution of regeneration in logged sites. The results reveal continuous but low recruitment in mature stands. The basal area of balsam fir (Abies balsamea (L.) Miller) had a strong negative effect on white pine regeneration. Regeneration was more abundant than expected on moister substrates, including moss, decaying wood and organic matter. White pine regeneration was noted in recently logged areas, where distance from remnant stands had a significant effect on the abundance of white pine regeneration. The northern limit of continuous distribution holds potential for white pine restoration, for example by preserving remnant white pine stands that can provide seed sources for natural regeneration in a shelterwood cut system, or in adjacent clearcut areas. This study illustrates that different management strategies should be used near northern range limits, where effects of site conditions and disturbance agents are different than in the center of a species’ range.

Genetical Genomics Identifies the Genetic Architecture for Growth and Weevil Resistance in Spruce

In plants, relationships between resistance to herbivorous insect pests and growth are typically controlled by complex interactions between genetically correlated traits. These relationships often result in tradeoffs in phenotypic expression. In this study we used genetical genomics to elucidate genetic relationships between tree growth and resistance to white pine terminal weevil (Pissodes strobi Peck.) in a pedigree population of interior spruce (Picea glauca, P. engelmannii and their hybrids) that was growing at Vernon, B.C. and segregating for weevil resistance. Genetical genomics uses genetic perturbations caused by allelic segregation in pedigrees to co-locate quantitative trait loci (QTLs) for gene expression and quantitative traits. Bark tissue of apical leaders from 188 trees was assayed for gene expression using a 21.8K spruce EST-spotted microarray; the same individuals were genotyped for 384 SNP markers for the genetic map. Many of the expression QTLs (eQTL) co-localized with resistance trait QTLs. For a composite resistance phenotype of six attack and oviposition traits, 149 positional candidate genes were identified. Resistance and growth QTLs also overlapped with eQTL hotspots along the genome suggesting that: 1) genetic pleiotropy of resistance and growth traits in interior spruce was substantial, and 2) master regulatory genes were important for weevil resistance in spruce. These results will enable future work on functional genetic studies of insect resistance in spruce, and provide valuable information about candidate genes for genetic improvement of spruce.

Resistance of Sitka spruce (Picea sitchensis (Bong.) Carr.) to white pine weevil (Pissodes strobi Peck): characterizing the bark defence mechanisms of resistant populations

It has long been known that strong expressions of resistance to the white pine weevil (Pissodes strobi Peck) exist in certain Sitka spruce (Picea sitchensis (Bong.) Carr.) populations, particularly among trees originating from the Fraser Valley and the Qualicum area of British Columbia (BC). In this paper, we characterize how resistance is manifested in these known resistant populations. Specifically, using cloned individuals, we investigated resistant traits associated with repellency, constitutive resin canals (CRC) and sclereid or stone cells. Results indicate significant population differences in the level of these traits between these two populations and susceptible populations. Fraser Valley populations had four times the sclereid density of susceptible populations. Although the Big Qualicum (East Vancouver Island) population had the same high resistance as the Haney (Fraser Valley) population, it was expressed primarily through increased CRC. Sclereid cell density had the strongest correlation to weevil attack followed by CRC. We discuss pathways by which two distinct resistant populations may have developed in this high weevil hazard region of south-west BC.

Genetically based resistance to the white pine weevil in jack pine and eastern white pine

White pine weevil (Pissodes strobi Peck) damage was evaluated in one white pine (Pinus strobus L.) and four jack pine(Pinus banksiana Lamb) half-sib family test sites to determine the role of tree genotype in resistance to the weevil. Halfsibfamily explained a significant proportion of the variation in weevil attack at all sites. Estimates of family (0.16-0.54)and individual (0.09-0.24) heritabilities of jack pine resistance to white pine weevil were moderate. Estimates of family(0.37) and individual (0.22) heritability of resistance of white pine to the weevil were also moderate when the percentageof test trees damaged by the weevil was relatively low, but were insignificant four years later when more than three-quartersof trees were damaged. Significant positive correlations between mean tree height and mean incidence of trees damagedby the weevil were observed for four of seven site-years but relationships were weak, suggesting that any cost, withrespect to height growth, to breeding weevil resistant trees may be small.Key words: Pinus, Pissodes strobi, trade-offs, tree improvement, tree resistance, white pine weevil.

Erratum: Terpenoid metabolite profiling in Sitka spruce identifies association of dehydroabietic acid, (+)-3-carene and terpinolene with resistance against white pine weevil

The white pine weevil (Pissodes strobi Peck) is an important insect pest in the Pacific Northwest that attacks the apical stem leaders of spruce (Picea spp.) causing damage to tree form, growth, and stand development. Because of attacks by weevils, Sitka spruce (P. sitchensis Bong.) is not commonly replanted as a commercial species in coastal British Columbia, despite its economic and ecological importance. In the last decade, the focus of research on Sitka spruce resistance against weevils has moved from silvicultural approaches to breeding for resistance. The British Columbia Ministry of Forests and Range, in collaboration with the Canadian Forest Service, has developed a successful program to screen populations and select tree genotypes for resistance to weevil attack. Part of this effort has been the establishment of clonebanks that contain genotypes from throughout the range of Sitka spruce. For metabolite profiling, using gas chromatography coupled with flame ionization detection or mass spectrometr...

Terpenoid metabolite profiling in Sitka spruce identifies association of dehydroabietic acid, (+)-3-carene, and terpinolene with resistance against white pine weevil

The white pine weevil ( Pissodes strobi Peck) is an important insect pest in the Pacific Northwest that attacks the apical stem leaders of spruce ( Picea spp.) causing damage to tree form, growth, and stand development. Because of attacks by weevils, Sitka spruce ( P. sitchensis Bong.) is not commonly replanted as a commercial species in coastal British Columbia, despite its economic and ecological importance. In the last decade, the focus of research on Sitka spruce resistance against weevils has moved from silvicultural approaches to breeding for resistance. The British Columbia Ministry of Forests and Range, in collaboration with the Canadian Forest Service, has developed a successful program to screen populations and select tree genotypes for resistance to weevil attack. Part of this effort has been the establishment of clonebanks that contain genotypes from throughout the range of Sitka spruce. For metabolite profiling, using gas chromatography coupled with flame ionization detection or mass spectrometry, we analysed 111 different genotypes to determine the relationship of mono- and di-terpenoid oleoresin compounds with the resistance rating. Dehydroabietic acid, a diterpene, was identified as a strong indicator of resistance. Two monoterpenes, (+)-3-carene and terpinolene, were also associated with resistance in genotypes originating from one of the areas (Haney) in which resistance has been noted.

Take Me to Your Leader: Does Early Successional Nonhost Vegetation Spatially InhibitPissodes strobi(Coleoptera: Curculionidae)?

The spatial influences of host and nonhost trees and shrubs on the colonization patterns of white pine weevil Pissodes strobi (Peck) were studied within a stand of planted interior hybrid spruce [Picea glauca (Moench) Voss x Picea engelmannii (Parry) ex Engelm.]. Planted spruce accounted for one third of all trees within the stand, whereas the remaining two thirds were comprised of early-successional nonhost vegetation, such as alder (Alnus spp.), paper birch (Betula papyrifera Marsh.), black cottonwood [Populus balsamifera ssp. trichocarpa (T. Ng.) Brayshaw], lodgepole pine [Pinus contorta (Dougl.) ex Loud.], trembling aspen (Populus tremuloides Michx), willow (Salix spp.), and Canadian buffaloberry [Shepherdia canadensis (L.) Nutt.]. Unlike the spruce trees, nonhost vegetation in the stand was not uniformly distributed. Spatial point process models showed that Canadian buffaloberry, paper birch, black cottonwoood, and trembling aspen had negative associations with damage caused by the weevil, even though the density of the insects' hosts in these areas did not change. Moreover, knowing the locations of these nonhost trees provided as much, or more, inference about the locations of weevil-attacked trees as knowing the locations of suitable or preferred host trees (i.e., those larger in size). Nonhost volatiles, the alteration of soil composition, and overstory shade are discussed as potential explanatory factors for the patterns observed. New research avenues are suggested to determine whether nonhost vegetation in early successional stands might be an additional tool in the management of these insects in commercially important forests.

The effects of herbaceous and woody competition on planted white pine in a clearcut site

We investigated the effects of herbaceous and woody vegetation control on the survival and growth of planted eastern white pine ( Pinus strobus L.) seedlings through six growing seasons. Herbaceous vegetation control involved the suppression of grasses, forbs, ferns, and low-shrubs, and was maintained for 0, 2, or 4 years after white pine seedlings were planted. Woody control involved the removal of all tall-shrub and deciduous trees, and was conducted at the time of planting, at the end of the second or fifth growing seasons, or not at all. Seedling height and basal diameter responded positively and proportionally to duration of herbaceous vegetation control. Gains associated with woody control were generally not significant unless some degree of herbaceous vegetation control was also conducted. Only herbaceous control increased pine crown closure and rate of crown closure. Herbaceous control and the presence of 5000–15,000 stems per ha of young overtopping aspen were associated with reduced weevil ( Pissodes strobi Peck.) injury and increased pine height growth. The study suggests that white pine restoration strategies on clearcut sites should focus on the proactive, early management of understory vegetation and the gradual reduction of overtopping cover from woody vegetation to create a seedling light environment that supports acceptable growth with minimal weevil damage.

Molecular characterization of the entomopathogenic fungiLecanicilliumspp. (Deuteromycota: Hyphomycetes) isolated from white pine weevil,Pissodes strobi(Coleoptera: Curculionidae), in British Columbia

AbstractThe entomopathogenic fungal genusLecanicilliumGams and Zare includes species that are highly pathogenic to many genera of insects. Three species,Lecanicillium longisporum(Petch) Zare and W. Gams,L. muscarium(Petch) Zare and W. Gams, andL. pissodisKope and Leal, were found to be entomopathogens of adult white pine weevils,Pissodes strobi(Peck), in coastal British Columbia. Morphological characteristics were used to identify these species, but variation in conidial shape and size made it difficult to classify some of the isolates into the correct species ofLecanicillium. To confirm the identity of theseLecanicilliumspecies, we used molecular tools such as polymerase chain reaction – restriction fragment length polymorphism and DNA sequencing.

Effects of temperature and water activity on Lecanicillium spp. conidia germination and growth, and mycosis of Pissodes strobi

Selecting entomopathogenic fungal isolates for use as biocontrol agents requires an assessment of their growth and virulence characteristics as affected by environmental conditions. Here we demonstrate a wide temperature and moisture range for colony growth, effective conidial germination and virulence against Pissodes strobi Peck (white pine weevil) of several isolates of Lecanicillium Gams and Zare, an entomopathogenic fungus distributed worldwide and indigenous to forests on Vancouver Island, British Columbia, Canada. In order to examine the potential Lecanicillium as a biological control agent, the pathogenicity of isolates collected from different geographical locations on P. strobi cadavers was assessed, and colony growth at different temperatures was evaluated. Colony growth was evident between 5 and 30°C, with optimal growth occurring at 25°C. Various combinations of water activity (0.55, 0.76, 0.85 and 0.99 a w) and temperature (10, 15, 20, and 25°C) were also used to evaluate environmental impacts on conidial germination and cumulative mycosis of adult P. strobi. Certain Lecanicillium isolates displayed xerophilic (0.85 a w) or psychrophilic (10°C) growth optima. Ultimately, identifying the abiotic limits of this entomopathogenic fungus will be used to determine which isolates have potential for future in situ biocontrol trials.

White pine weevil (Pissodes strobi) biological performance is unaffected by the jasmonic acid or wound-induced defense response in Norway spruce (Picea abies)

In eastern Canada, the white pine weevil (Pissodes strobi Peck) is a pest of several native pine and spruce species and of the introduced species, Norway spruce (Picea abies Karst). We evaluated the feeding activities, oviposition and rate of adult emergence of white pine weevil on field-grown Norway spruce subjected to jasmonic acid or wounding pretreatments. We also monitored the host-plant reaction to white pine weevil attack, jasmonic acid and wounding treatments by quantifying several mono- and sesquiterpenes in bark and characterizing some molecular aspects of the terpenoid response. Two cDNA sequences were identified that had a high percentage of identity with genes encoding monoterpene or sesquiterpene synthases. Both putative terpene synthase genes showed distinctive profiles in Norway spruce bark and needles following all treatments. Although the Norway spruce trees showed different physiological responses to mechanical wounding and white pine weevil attack, transcript activity of the gene encoding terpenoid synthase and consequent accumulation of terpenoid resin did not significantly affect the weevils' feeding activities, oviposition or rate of adult emergence.

Impact du charançon du pin blanc (Pissodes strobi Peck) dans les plantations d'épinettes de Norvège (Picea abies [L.] Karst.) Partie 1 : Productivité et qualité des sciages

A study to assess the effects that major deformations in merchantable stems of Norway spruce (Picea abies [L.] Karst.), caused by the white pine weevil (Pissodes strobi [Peck]), have on lumber productivity and quality was performed on logs obtained from the second commercial thinning operation in three weevil-affected plantations. Deformed stems were found to be 6.3% shorter than undeformed stems and their lumber characteristics — merchantable volume, number of board feet and lumber monetary value — were 14.7%, 20.6% and 23.7% lower, respectively. However, when the respective proportions of deformed and undeformed stems were analyzed for a given plantation over a time horizon of a complete rotation, these shortfalls almost disappeared, with a loss of less than 3% being noted for total merchantable volume. The presence/absence of major deformations had no effect on visual grading of the lumber, which considers defects such as wane, knots and compression wood. For two of the three sites studied, almost 75% of the lumber was graded as Select Structural, No. 1 or No. 2. The plantation site and its characteristics (spacing and level of thinning) were found to have a more significant effect than deformations on productivity, lumber quality and monetary value. Furthermore, using the same methodology, one of the Norway spruce sites was compared with a white spruce (Picea glauca [Moench] Voss) plantation containing trees of similar quality and height but no weevil problems. The Norway spruce stems, including those with deformations, were found to yield higher merchantable and usable log volumes, a larger number of board feet and a higher monetary value than the white spruce. On average, for the diameter-at-breast-height values tested — 14 to 23 cm — the monetary value of the lumber was 26% higher for Norway spruce. These findings are largely attributable to the less pronounced taper of Norway spruce. In conclusion, in spite of weevil attacks and its negative impact, Norway spruce trees growing on sites of moderate to very good quality maintain lumber potential, in terms of both quantity and quality for second thinning logs. The negative impact should gradually diminish at the time of next thinnings and final harvest. Key words: white pine weevil, Pissodes strobi (Peck), Norway spruce, Picea abies (L.) Karst., wood quality, plantation, productivity

Wound-Induced Terpene Synthase Gene Expression in Sitka Spruce That Exhibit Resistance or Susceptibility to Attack by the White Pine Weevil

We analyzed the expression pattern of various terpene synthase (TPS) genes in response to a wounding injury applied to the apical leader of Sitka spruce (Picea sitchensis Bong. Carr.) genotypes known to be resistant (R) or susceptible (S) to white pine weevil (Pissodes strobi Peck.) attack. The purpose was to test if differences in constitutive or wound-induced TPS expression can be associated with established weevil resistance. All wounding treatments were conducted on 9-year-old R and S trees growing under natural field conditions within the range of variation for weevil R and S genotypes. Representative cDNAs of the monoterpene synthase (mono-TPS), sesquiterpene synthase (sesqui-TPS), and diterpene synthase (di-TPS) classes were isolated from Sitka spruce to assess TPS transcript levels. Based on amino acid sequence similarity, the cDNAs resemble Norway spruce (Picea abies) (-)-linalool synthase (mono-TPS; PsTPS-Linl) and levopimaradiene/abietadiene synthase (di-TPS; PsTPS-LASl), and grand fir (Abies grandis) delta-selinene synthase (sesqui-TPS; PsTPS-Sell). One other mono-TPS was functionally identified as (-)-limonene synthase (PsTPS-Lim). No significant difference in constitutive expression levels for these TPSs was detected between R and S trees. However, over a postwounding period of 16 d, only R trees exhibited significant transcript accumulation for the mono- and sesqui-TPS tested. Both R and S trees exhibited a significant accumulation of PsTPS-LASl transcripts. An assessment of traumatic resin duct formation in wounded leaders showed that both R and S trees responded by forming traumatic resin ducts; however, the magnitude of this response was significantly greater in R trees. Collectively, our data imply that the induced resinosis response is an important aspect of defense in weevil R Sitka spruce trees growing under natural conditions.

Insect attack and wounding induce traumatic resin duct development and gene expression of (-)-pinene synthase in Sitka spruce.

Conifers possess inducible terpenoid defense systems. These systems are associated with the formation of traumatic resin ducts (TRD) and are underpinned by enhanced gene expression and activity of terpene synthases (TPS), enzymes responsible for oleoresin formation. We first determined that Sitka spruce (Picea sitchensis [Bong.] Carriere) had the capacity for TRD formation by mechanically wounding representative trees. We then proceeded to investigate whether the white pine weevil (Pissodes strobi Peck.), a stem-boring insect, can influence the expression of genes encoding monoterpene synthases (mono-tps) in Sitka spruce. We went on to compare this response with the effects of a simulated insect attack by drill wounding. A significant increase in mono-tps transcript level was observed in the leaders of lateral branches of weevil-attacked and mechanically wounded trees. In this study, weevils induced a more rapid enhancement of mono-tps gene expression. A full-length Sitka spruce mono-tps cDNA (PsTPS2) was isolated, expressed in Escherichia coli, and functionally identified as (-)-pinene synthase. The recombinant (-)-pinene synthase catalyzes the formation of (-)-alpha-pinene and (-)-beta-pinene, both of which are known constituents of stem oleoresin in Sitka spruce and increase in abundance after weevil attack. These data suggest that increased (-)-pinene synthase gene expression is an important element of the direct defense system deployed in Sitka spruce after insect attack.

Biological performance of the white pine weevil in relation to the anatomy of the resin canal system of four different host species

The anatomy of the resin canal system was observed on lateral branches of four host species of the white pine weevil (Pissodes strobi Peck) in relation to weevil performance. The host species studied were Norway spruce (Picea abies (L.) Karst.), white spruce (Picea glauca (Moench) Voss), red spruce (Picea rubens Sarg.), and white pine (Pinus strobus L.). Survival, number, and mass of adult weevils were measured on attacked terminal leaders collected before adult emergence. One uppermost lateral branch was collected at the base of each attacked leader. Cross sections of these lateral branches were observed to measure the number, diameter, depth, and density of inner and outer resin canals. Nearly all resin canal measurements differed significantly among species, with white pine differing greatly from the other species with larger canals and lower canal density. Correlation analysis demonstrated that the anatomy of the resin canal system was principally related to adult mass, with the most important variable being the density of inner canals (r = –0.54). Trees characterized by low density of large inner resin canals, like white pine, seemed to favour mass gain in adult weevils. The present study suggests that a high density of inner resin canals constrains the insect to feed on canals early in larval development, which subsequently reduces weevil mass.

Biological performance of the white pine weevil in different host species and in two ecological regions of southern Quebec

The performance of the white pine weevil (Pissodes strobi Peck) was studied on five different host species: Norway spruce (Picea abies (L.) Karst.), white spruce (Picea glauca (Moench) Voss), red spruce (Picea rubens Sarg.), jack pine (Pinus banksiana Lamb.), and eastern white pine (Pinus strobus L.). Attacked terminal leaders were collected prior to adult emergence, within two different ecological regions of Quebec, the Outaouais and Appalaches regions. According to their natural range, jack pine was studied only in the Outaouais region and red spruce only in the Appalaches one. Weevil performance did not differ between regions but differed among host species. The number of eggs laid per leader was greatest on jack pine, white pine, and Norway spruce (279, 219, and 218 eggs per leader, respectively). Adults emerging from white pine were the heaviest (0.0104 g). The number of adults per leader was greater on Norway spruce and white pine (34 and 23 adults, respectively), and survival tended to be greater on Norway spruce and white spruce leaders (18 and 15%, respectively). Norway spruce had the longest leaders, and jack pine had the thickest ones. Leader dimensions were correlated with all variables of weevil performance, except insect survival, but these characteristics explain only a small part of the variation in weevil performance. Norway spruce and white pine can be considered favourable hosts for rapid population buildup according to the high number of emerging adults per attacked leader.