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Managing multiple forest insect pests and diseases is challenging. For example, in eastern white pine (Pinus strobus) stands whereas partial shading and high seedling density is encouraged to reduce damage by white pine blister rust (Cronartium ribicola) and white pine weevil (Pissodes strobi), dense conditions in the understory may increase damage by foliar diseases such as brown spot needle blight (Lecanosticta acicola) and Caliciopsis canker (Caliciopsis pinea). We evaluated the effect of silvicultural treatments, shelterwoods (residual basal area

Spruce weevil (Pissodes strobi) is a significant pest of regenerating spruce (Picea) and pine (Pinus) forests in North America. Weevil larvae feed in the bark, phloem, cambium, and outer xylem of apical shoots, causing stunted growth or mortality of young trees. We identified and characterized constitutive and weevil‐induced patterns of Sitka spruce (Picea sitchensis) transcriptomes in weevil‐resistant (R) and susceptible (S) trees using RNA sequencing (RNA‐seq) and differential expression (DE) analyses. We developed a statistical model for the analysis of RNA‐seq data from treatment experiments with a 2 × 3 factorial design to differentiate insect‐induced responses from the effects of mechanical damage. Across the different comparisons, we identified two major transcriptome contrasts: A large set of genes that was constitutively DE between R and S trees, and another set of genes that was DE in weevil‐induced S‐trees. The constitutive transcriptome unique to R trees appeared to be attuned to defense, while the constitutive transcriptome unique to S trees was enriched for growth‐related transcripts. Notably, a set of transcripts annotated as "fungal" was detected consistently in the transcriptomes. Fungal transcripts were identified as DE in the comparison of R and S trees and in the weevil‐affected DE transcriptome of S trees, suggesting a potential microbiome role in this conifer‐insect interaction. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

White pine weevil (Pissodes strobi, Peck.) is a native forest insect pest in the Pacific Northwest of North America that attacks species of spruce (Picea spp.) and pine (Pinus spp.). Young Sitka spruce [Picea sitchensis (Bong.) Carr.] trees are particularly susceptible to weevil attack. Pockets of naturally occurring Sitka spruce resistance have been identified in high weevil hazard areas in coastal British Columbia. In this study, we characterize behavioral, physiological and reproductive responses of weevils to an extremely resistant Sitka spruce genotype (H898) in comparison to a highly susceptible genotype (Q903). The experiments relied on a large number of three-year-old clonally propagated trees and were therefore restricted to two contrasting Sitka spruce genotypes. When exposed to resistant trees, both male and female weevils were deterred during host selection and mating, females showed delayed or reduced ovary development, and successful reproduction of weevils was prevented on resistant trees.

Conifers possess an array of physical and chemical defences against stem-boring insects. Stone cells provide a physical defence associated with resistance against bark beetles and weevils. In Sitka spruce ( Picea sitchensis), abundance of stone cells in the cortex of apical shoots is positively correlated with resistance to white pine weevil ( Pissodes strobi). We identified histological, biochemical and molecular differences in the stone cell phenotype of weevil resistant (R) or susceptible (S) Sitka spruce genotypes. R trees displayed significantly higher quantities of cortical stone cells near the apical shoot node, the primary site for weevil feeding. Lignin, cellulose, xylan and mannan were the most abundant components of stone cell secondary walls, respectively. Lignin composition of stone cells isolated from R trees contained a higher percentage of G-lignin compared with S trees. Transcript profiling revealed higher transcript abundance in the R genotype of coumarate 3-hydroxylase, a key monolignol biosynthetic gene. Developing stone cells in current year apical shoots incorporated fluorescent-tagged monolignol into the secondary cell wall, while mature stone cells of previous year apical shoots did not. Stone cell development is an ephemeral process, and fortification of shoot tips in R trees is an effective strategy against insect feeding. [ABSTRACT FROM AUTHOR]

Tree mortality because of beetle outbreaks has become substantial and widespread in conifer forests in western North America. A number of environmental and physiological factors influence patterns of mortality. Tree diversity may reduce the severity and extent of insect damage to host trees by providing associational resistance, but the existence and importance of associational resistance varies by forest type and by tree and insect species. We assessed whether plot-level tree diversity contributed to survival of Engelmann spruce ( Picea engelmannii Parry ex Engelm.) following a spruce beetle ( Dendroctonus rufipennis Kirby) epidemic. Our study plots comprised 2 to 5 tree species including Engelmann spruce, subalpine fir ( Abies lasiocarpa (Hook) Nutt.), Douglas-fir ( Pseudostuga menziesii (Mirb.) Franco), quaking aspen ( Populus tremuloides Michx.), and white fir ( Abies concolor (Gordon & Glend.) Hildebr.). We used a model-selection analysis to compare the importance of tree diversity with other known factors that influence spruce survival. We found lower rates of spruce survival in stands where spruce was the dominant tree species (by percent of stand density index) and higher survival in stands where nonspruce conifers (Douglas-fir, subalpine, and white fir) were dominant. We also found that tree diversity (Shannon index) did not show a positive correlation to spruce survival and that there was no additional benefit derived from the presence of aspen, which has higher phylogenetic distance from Engelmann spruce than the other trees in this study. The relationship between diversity and survival is complicated by factors that naturally co-vary with diversity, such as elevation, aspect, and stand density of spruce. Our results best support an explanation that if associational resistance does increase spruce survival during a beetle epidemic, it is due to host or resource dilution, which may be an indirect effect of higher stand diversity. [ABSTRACT FROM AUTHOR]

Highlights: [•] Chitinase full length cDNAs were cloned from interior spruce and lodgepole pine. [•] Chitinolytic activity was established for class I chitinases. [•] Conifer chitinases were induced by fungal inoculation and insect feeding. [ABSTRACT FROM AUTHOR]

In central British Columbia (BC), forest management practices have altered natural stand development pathways by controlling “non commercial” tree species and other competing species with the objective of maximizing crop tree growth. This potentially decreases overall diversity within the stand. We conducted a retrospective study on a 13-year-old stand to investigate the impacts of vegetation management with glyphosate on tree growth, species diversity and forest health in central BC. Results revealed that spruce was marginally taller than birch in the herbicide treated area and significantly shorter than birch in the untreated area. There was no difference in spruce diameter at breast height (DBH) and mean stem volume by treatment. White pine weevil attack was significantly reduced in the untreated area. In total, 133 plant species were recorded from 2002 to 2006, but 30% of the species present in 2002 were not present in 2006. Species' richness and alpha diversity were similar between treatments but beta diversity was relatively low indicating little treatment effect. There was a greater occurrence and abundance of “weedy” and pioneer species in the herbicide-treated area. Overall, this study suggests that glyphosate application does not remove all birch and showed minimal or no impact on under-story vegetation. Therefore, a move away from broadcast vegetation control to spot control where warranted could result in better tree growth, improved forest health and structural diversity. [ABSTRACT FROM PUBLISHER]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article discusses the results of a study that examined the phototactic behavior of Armand pine bark weevil, Pissodes punctatus which is a destructive bark weevil on the Armand pine, Pinus armandii. The study showed that Pissodes punctatus is most active in the day, kept still at night and is attracted to monochromatic lights, except the red light. It concluded that the weevil's phototactic behavior is both a color and intensity preference.

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 ESTspotted 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. [ABSTRACT FROM AUTHOR]

Attack by the white pine weevil has notably reduced Sitka spruce productivity in British Columbia (BC) (Canada) and western US. By the 1970s, the BC Ministry of Forests established provenance trials of Sitka spruce with the objective of detecting usable genetic resistance to weevil. These early trials reported significant weevil resistance and allowed the production of the first (F1) controlled-cross progeny generation with demonstrable weevil resistance (R) or susceptibility (S). This study reports results of the screening for weevil resistance and the levels of constitutive defenses of this F1 Sitka spruce progeny. Progeny from resistant parents (R × R progeny) sustained significantly fewer weevil attacks than progeny from susceptible parents (S × S progeny) or progeny with one resistant and one susceptible parent (R × S progeny). Individual and family heritability estimates of the weevil resistance were 0.5 and 0.9, respectively. Constitutive defenses, measured by resin canal and sclereid cell density in the cortex, were significantly higher in R × R progeny than in R × S or S × S progeny. We observed a negative correlation between the percentage of trees attacked in each cross and the average density of the resin canals or sclereid cells for each cross. [ABSTRACT FROM AUTHOR]

Conifers are extremely long-lived plants that have evolved complex chemical defenses in the form of oleoresin terpenoids to resist attack from pathogens and herbivores. In these species, terpenoid diversity is determined by the size and composition of the terpene synthase (TPS) gene family and the single- and multi-product profiles of these enzymes. The monoterpene (+)-3-carene is associated with resistance of Sitka spruce ( Picea sitchensis) to white pine weevil ( Pissodes strobi). We used a combined genomic, proteomic and biochemical approach to analyze the (+)-3-carene phenotype in two contrasting Sitka spruce genotypes. Resistant trees produced significantly higher levels of (+)-3-carene than susceptible trees, in which only trace amounts were detected. Biosynthesis of (+)-3-carene is controlled, at the genome level, by a small family of closely related (+)-3-carene synthase ( PsTPS-3car) genes (82-95% amino acid sequence identity). Transcript profiling identified one PsTPS-3car gene ( PsTPS-3car1) that is expressed in both genotypes, one gene ( PsTPS-3car2) that is expressed only in resistant trees, and one gene ( PsTPS-3car3) that is expressed only in susceptible trees. The PsTPS-3car2 gene was not detected in genomic DNA of susceptible trees. Target-specific selected reaction monitoring confirmed this pattern of differential expression of members of the PsTPS-3car family at the proteome level. Kinetic characterization of the recombinant PsTPS-3car enzymes identified differences in the activities of PsTPS-3car2 and PsTPS-3car3 as a factor contributing to the different (+)-3-carene profiles of resistant and susceptible trees. In conclusion, variation of the (+)-3-carene phenotype is controlled by copy number variation of PsTPS-3car genes, variation of gene and protein expression, and variation in catalytic efficiencies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tree susceptibility to bark beetle-caused mortality has been linked to stand characteristics such as basal area (BA) and average tree size, factors that can be manipulated through partial cutting. There is no experimental evidence, however, demonstrating the efficacy of partial cutting in spruce type. Such experiments are very difficult to complete because of the inability to manipulate bark beetle populations needed to challenge treated stands. To circumvent this difficulty, we identified spruce stands that were partially cut (for nonexperimental reasons) in advance of beetle activity and compared beetle-caused mortality to that in nearby spruce stands that were not treated. Treated stands had fewer infested stems and less infested BA than untreated stands, as well as smaller proportions of infested stems and BA. Untreated stands, however, had more residual spruce stems and BA than treated stands. Most of this difference was among stems 3-11 in. dbh with little difference in survivorship among larger stems. Spruce regeneration was not significantly different among treated and untreated stands. Spruce stand density index, spruce BA, and the number of spruce stems >11 in. dbh were the stand variables most strongly correlated with host mortality measurements. Insect population pressure appears to influence the degree of protection to residual spruce following partial cutting. [ABSTRACT FROM AUTHOR]

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 Engeim.]. 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 [Popular balsamifera ssp. trichocarpa (T. Ng.) Brayshaw], lodgepole pine [Pinus contorta (Dougl.) ex Loud. ], trembling aspen (Popular 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. [ABSTRACT FROM AUTHOR]

Our goal was to quantify tree- and branch-level components of growth response to three silvicultural treatments (STs), and weevil incidence in white pine (Pinus strobus L.) from large, central populations in Ontario (ON) versus small, isolated populations in Newfoundland (NL). Light levels were 100%, 42.0%, and 20.4% transmittance for the full-sun, intermediate-shade, and high-shade STs. After 8 years, the overall incidence of weevil infestation was 42.1%, 23.4%, and 13.7% for the full-sun, intermediate-shade, and high-shade STs, respectively (P < 0.001). Weevil impact on total height and volume averaged –13.2% and –11.8%. Analysis of dominant lateral shoots showed that ON populations had 32% longer shoots than the NL populations. Bud set difference was a primary determinant of shoot-length growth differences between regions: Julian days 171 and 184 for the NL and ON populations, respectively. The primary determining factors related to shoot length were the number of needle bundles and region, driven by light levels and day length, respectively, and the internode length, probably through inbreeding effects. Total height and diameter showed a positive curvilinear relationship to light level. To maximize fitness, NL conservation strategies should also now consider introducing adaptive trait variation in the context of anticipated climate change. [ABSTRACT FROM AUTHOR]

Abstract: Sitka spruce (Picea sitchensis (Bong.) Carr), white spruce (P. glauca (Moench) Voss) and Engelmann spruce (P. engelmanni (Parry)) plantations in British Columbia (B.C.), Canada, have come under serious attack from the white pine weevil, Pissodes strobi (Peck) (Coleoptera: Curculionidae). This pest attacks and destroys the terminal leader of the tree, causing serious growth losses and stem deformities. Since 1993, we have conducted a series of screening trials to search for spruce with resistance to the white pine weevil. Spruce tree selections from across the range of the species have been planted in several replicated trials. At 12 of these trial sites, in order to accelerate the screening process, local insect populations were augmented by adding reared weevils to the site. Results from our two oldest trials, at Jordan River and Cowichan Lake (planted in 1994), both on Vancouver Island, B.C., indicate that screening for weevil resistance can be effectively accomplished by using the weevil population augmentation method. Consistent selections could be obtained in trials with as few as 10 replicates per family. If weevil attack rates of 50% cumulative attack are obtained, then consistent selections may be obtained in as little as 4 years, which is a fairly quick turn-around time for studying resistance in trees. [Copyright &y& Elsevier]

Copyright of Canadian Entomologist is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Analysis of expressed sequence tags (ESTs) and full-length (FL)cDNAs from species of spruce (Picea spp.) revealed a family of 35 unique dirigent proteins (DIR) and DIR-like proteins. Phylogenetic analysis indicates the spruce DIR and DIR-like genes cluster into three distinct subfamilies, DIR-a, DIR-b/d, and DIR-f, of a larger plant DIR and DIR-like gene family. Gene-specific primers were designed for 31 unique spruce DIR family genes, and closely related isoforms, and used to evaluate patterns of constitutive expression, as well as responses to herbivory by stem-boring insects (i.e., white pine weevil, Pissodes strobi) in bark tissue and defoliating insects (i.e., western spruce budworm, Choristoneura occidentalis) in green apical shoots. Furthermore, meta-analysis of microarray gene expression data obtained from a series of independent experiments using the same 16.7K cDNA array platform identified several distinct expression clusters of the spruce DIR transcriptome closely matching phylogenetic clusters of sequence similarity. Members of the DIR-a family, which also contains functionally characterized DIR from other plant species, are most prominent for their induced response to feeding by weevils on Sitka spruce bark. [Copyright &y& Elsevier]

Studies were conducted under laboratory conditions to document the potential of Beauveria bassiana conidia applications for controlling the white pine weevil, Pissodes strobi (Peck). A screening test including six B. bassiana isolates allowed us to demonstrate that CFL (Centre de Foresterie des Laurentides) and IP-CPB (Île Perrault-charançon du pin blanc) were the most virulent isolates among the ones tested, with percentages of mortality after 3 weeks of 73% and 85.5%, respectively. These two B. basiana isolates were applied either onto soil or branch sections to compare the effectiveness of these potential control strategies. Greater than 75% mortality was observed within 3 weeks for both modes of application using suspensions of B. bassiana at a concentration of 1.0 × 108 (soil application) and 1.0 × 109 conidia/ml (branch application). The results demonstrate for the first time that B. bassiana is an effective entomopathogen against P. strobi. [ABSTRACT FROM AUTHOR]

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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. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Conifers are resistant to attack from a large number of potential herbivores or pathogens. Previous molecular and biochemical characterization of selected conifer defence systems support a model of multigenic, constitutive and induced defences that act on invading insects via physical, chemical, biochemical or ecological (multitrophic) mechanisms. However, the genomic foundation of the complex defence and resistance mechanisms of conifers is largely unknown. As part of a genomics strategy to characterize inducible defences and possible resistance mechanisms of conifers against insect herbivory, we developed a cDNA microarray building upon a new spruce ( Picea spp.) expressed sequence tag resource. This first-generation spruce cDNA microarray contains 9720 cDNA elements representing c. 5500 unique genes. We used this array to monitor gene expression in Sitka spruce ( Picea sitchensis) bark in response to herbivory by white pine weevils ( Pissodes strobi, Curculionidae) or wounding, and in young shoot tips in response to western spruce budworm ( Choristoneura occidentalis, Lepidopterae) feeding. Weevils are stem-boring insects that feed on phloem, while budworms are foliage feeding larvae that consume needles and young shoot tips. Both insect species and wounding treatment caused substantial changes of the host plant transcriptome detected in each case by differential gene expression of several thousand array elements at 1 or 2 d after the onset of treatment. Overall, there was considerable overlap among differentially expressed gene sets from these three stress treatments. Functional classification of the induced transcripts revealed genes with roles in general plant defence, octadecanoid and ethylene signalling, transport, secondary metabolism, and transcriptional regulation. Several genes involved in primary metabolic processes such as photosynthesis were down-regulated upon insect feeding or wounding, fitting with the concept of dynamic resource allocation in plant defence. Refined expression analysis using gene-specific primers and real-time PCR for selected transcripts was in agreement with microarray results for most genes tested. This study provides the first large-scale survey of insect-induced defence transcripts in a gymnosperm and provides a platform for functional investigation of plant–insect interactions in spruce. Induction of spruce genes of octadecanoid and ethylene signalling, terpenoid biosynthesis, and phenolic secondary metabolism are discussed in more detail. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of the study was to demonstrate the importance of bark polar fraction from Norway spruce [ Picea abies (L.) Karst.] terminal leaders on the feeding activity and oviposition process of the female white pine weevil, Pissodes strobi (Peck). The bark polar fraction was extracted with a ternary solvent [chloroform, methanol and water (12 : 5 : 3)]. This extracted fraction was added, at different concentrations, to an artificial diet on which mated female white pine weevils could feed and oviposit. The bark polar fraction of Norway spruce terminal leaders promoted white pine weevil oviposition compared with untreated artificial diet. The results of this study contributed to the development of an efficient artificial rearing substrate required to better understand the interactions between white pine weevil and its host plants. The importance of more specific compounds found in the polar fraction could eventually help produce more resistant trees. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Entomologist is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Controlled-cross progeny of interior spruce (Picea glauca (Moench) Voss × Picea engelmanni Parry ex Engelm.) parents ranked as resistant or susceptible to the white pine weevil, Pissodes strobi (Peck) were screened for resistance to the same insect by augmentation of the trial site with weevils. Progeny from two resistant parents (R × R progeny) sustained significantly fewer weevil attacks (13% of the trees were attacked) in the year following the augmentation, than progeny from susceptible parents (S × S progeny) (68% of the trees were attacked). Progeny obtained by crossing one resistant and one susceptible parent (R × S progeny) sustained intermediate attack levels (47% were attacked). Characteristics of the bark resin canals of the crosses were explored using microscopy techniques. Bark resin canal density was highest in R × R progeny, lowest in S × S progeny and intermediate in R × S progeny. There was a negative correlation between the percentage of trees attacked in each cross and the average density of the outer resin canals for each cross. A discriminant function was developed that distinguished between resistant and susceptible progeny using bark characteristics. The function was characterized by positive coefficients for outer resin canal density and inner resin canal size, and a negative coefficient for bark thickness. Thus, trees with thin bark, large inner resin canals and dense outer resin canals are more likely to be resistant to P. strobi. [Copyright &y& Elsevier]

Examines the patterns of male and female reproductive success among white pine weevil, Pissodes strobi. Effect of weevils on the growth of Sitka spruce; Regimes under which matings among the species are conducted.

1 There is confusion in the literature concerning a possible reproductive diapause in the adult white pine weevil Pissodes strobi. 2 We evaluated the effects of temperature, photoperiod, feeding substrate and mating status on the sexual maturation and oviposition of female white pine weevils. 3 Less than 30% of female P. strobi became sexually mature and laid eggs without experiencing dormancy under a temperature regime of 2 °C for 4weeks. 4 Among the females that experienced a cold temperature treatment after emergence, 80% laid eggs after dormancy when exposed to a long-day (LD 16:8 h) photoperiod and 17.6% laid eggs when exposed to a short-day (LD8: 16h) photoperiod. 5 Significantly more eggs were laid by all the females (with and without a cold treatment) when subjected to a long-day photoperiod compared with a shortday photoperiod. 6 A period of cold temperature followed by exposure to a long-day photoperiod with warmer temperatures is required to break reproductive diapause and to obtain a good oviposition response in female P. strobi. 7 This study reveals the existence of much intraspecific variation in the response of the white pine weevil to temperature and photoperiod with respect to the induction and termination of reproductive diapause. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined several issues related to sexual reproduction in the white pine weevil. Effect of female age on offspring sex ratio; Materials and methods; Results and discussion.

Examines the geographic variation in resin canal defenses in seedlings from the Sitka spruce x white spruce introgression zone in British Columbia. Infliction of wound on the seedlings to simulate white pine weevil attack; Differences among the 18 provenances; Increase in constitutive resin canals.

The white pine weevil's (Pissodes strobi Peck) feeding, oviposition and emergence were studied in a 12-year-old (1998) white pine (Pinus strobus L.) progeny test established under a canopy of mature pioneer species in the Outaouais region (Notre-Dame-du-Laus, Quebec, Canada). The basal area of the overstory centred on 63 white pines was used as an indicator of forest cover. With overstory basal area ranging from 0 to 16 m²/ha, some white pine weevil performance parameters such as feeding and oviposition were significantly correlated with forest cover. However, others like the number of pupal chambers, emergence holes, partial survival index (emergence holes/chip-cocoon punctures) and total survival index (oviposition punctures/emergence holes) were not. Results showed that with an increase of forest cover, tree height was not affected but tree bole diameter was reduced. No relation was observed between leader diameter and the number of oviposition punctures. Even under a canopy, natural enemies (Lonchaea corticis Taylor and hymenoptera parasitoids) were also noted to reduce larval and pupal white pine weevil populations. [ABSTRACT FROM AUTHOR]

The article discusses a paper that offer survival time analysis of a white spruce tree with respect to the attack by the white pine weevil. Topics discussed include investigation of survival times of resistant and susceptible trees during trial of white spruce in the interior of British Columbia, Canada, study of survivorship of resistant trees with respect to susceptible trees and identification of survival times of white spruce trees followed by a lognormal distribution.

Abstract. 1. Eight generations of white pine weevil, Pissodes strobi (Peck), infesting the terminal shoots of young jack pine trees, were sampled as larvae, pupae, and adults between 1988 and 1995. 2. The density of adult weevils increased rapidly for the first 3 years of the study, then declined in the next 4 years. Between-generation rates of change in density of weevils were related to mean number of weevils produced per terminal shoot of the host tree. Net increases in population density followed years in which a relatively high number of weevils emerged per terminal shoot and vice versa. 3. The mean number of weevils emerging per terminal shoot was determined by survival of weevils between the end of the larval stage and the successful emergence of adult weevils. 4. There was no clear relationship between survival of the post-feeding stages of the weevil and rates of parasitism or bird predation on these same stages. There was, however, a strong negative relationship between survival of weevils within the terminal shoot and the abundance of the facultative dipteran predator Lonchaea corticis Taylor. 5. The relationship among generational rates of change in populations, survival, and predation was evident irrespective of the age of the trees infested, suggesting that population dynamics of the weevil may be influenced as much by local predation pressure as by physical and biotic changes associated with growth of the young host trees. [ABSTRACT FROM AUTHOR]

The traumatic wound response of families of white spruce, Picea glauca (Moench) Voss, resistant or susceptible to the white pine weevil, Pissodes strobi (Peck), were compared after simulated weevil damage. Leaders from 331 trees were wounded just below the apical bud in the spring, coinciding with the natural time of weevil oviposition. A portable 1-mm diameter drill was used to drill 24 holes per leader. Leaders were removed in the fall and examined for evidence of traumatic resin canal formation. Drilled trees had a traumatic wound response 8 times greater than that of undrilled trees; however, undrilled trees also formed some resin canals in response to unknown causes. In the drilled trees, the traumatic wound response extended into the lower part of the leader, where it could possibly affect older larvae. Trees from resistant families responded with greater intensity than trees from susceptible families, by producing multiple rings of traumatic resin canals. Trees from resistant families also responded more rapidly than trees from susceptible families based on number of cells to the first ring of traumatic resin canals. Trees from some resistant families exhibited no traumatic resin canal formation, showing considerable within-family variation and suggesting that other resistance mechanisms might be important. In the year after drilling, there was a reduction in tree diameter growth and trees suffered a reduction in constitutive resin canals in the bark, which suggests some energetic cost of traumatic resin production. There was no indication that the extent of constitutive defenses, as measured by density of cortical resin canals before wounding, was related to the ability to produce traumatic resin canals. Screening trees based on their capacity to produce traumatic resin canals may be useful in selecting genotypes resistant to white pine weevil. [ABSTRACT FROM PUBLISHER]