Periodic growth and volume losses in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees in one stand defoliated four times in their lifetime by western spruce budworm (Choristoneuraoccidentalis (Freeman)) are reported. Losses were calculated by comparing periodic growth for the years of reduced ring increment with potential growth estimated using the IMPACT growth loss program. Proportional losses in stem radius and cross-sectional area remained approximately constant or declined slightly from tree top to base; losses differed at all stem levels among the infestations. Average gross volume losses per tree relative to the potential volume the trees should have reached at the end of each loss period were 17, 15, 8, and 13% for the 1920's, 1940's, 1950's, and 1970's infestations, respectively. In the last infestation, losses ranged from 9% in trees defoliated from 1 to 50%, to 18% in trees defoliated 91–100%. Cumulative tree volume losses, calculated by adjusting growth during all loss periods to their potential values, were estimated to be 44% of the potential volume the trees should have reached by 1977 had the trees never been defoliated. On a per hectare basis, the 1970's infestation in this stand caused an estimated 60 m3 (18%) loss, comprising 40 m3 (12%) owing to tree mortality and 20 m3 (6%) of growth deficit in the surviving trees.
White pine weevil Pissodes strobi behaviour was observed in Le comportement du charanqon du pin blanc Pissodes strobi a five-year-old plantation of white spruce in Vernon, British a Ct C CtudiC dans une plantation de cinq ans d'Cpinetle blanche localColumbia. Seasonal weevil-host interactions were monitored in is& B Vernon en Colombie-Britannique. Les interactions charanqonfour susceptible and four putatively resistant reciprocal cross famh6te ant Ct-~diks chez q u m P&S susceptibles et qutre P&S ily pairs in three of five replicates. Classification of susceptibility potentiellement rksistantes issues de croisements rkciproques to weevil attack was based on previous weevil attack history.d'une m6me famille et pour trois des cinq replicats. La classifiperformance of eight reciprocal cross pairs was ranked as a cation de la susceptibilit6 B l'attaque du charanqon reposait sur function of visitation, ov~pos~t~on and brood establishment resultl'historique des prkCdentes attaques. La performance de huit des ing in top-kill, The four putatively resistant family crosses paires issues de croisements rCciproques Ctait classCe en tant que ranked 1 to 4 for resistance to weevil attack, while the four susde la prCsence, de l'emplacement des oeufs et de ceptible crosses were ranked 5 to 8 and were consistently attacked. l'emplacement des lames entdnant la mort de la flkhe. Les quatre croisements potentiellement rksistants ont Ct C classis de 1 B Seasonal and diurnal movement was using mark-4 en fonction de la resistance B l'attaque du charanqon, tandis que recapture techniques. Diurnally, weevils moved within the tree. les croisements susceptibles CtC classCs de et Feeding occurred at dawn in the leader and laterals after which conhuellement &qUCs. Les d*lacements saisonnim et ractivweevils moved down the tree into the forest floor during the high it6 dime kt6 enregistr~s selon une technique de et mkl-mnmer temperatures. Later in the season weevils fed in midde capture. Au cours de la journte, le charangon se deplace morning on the leader and on the under-sides of lateral branchdans 19arbre. ~~~l i~~~t~t i~~ se fait au cr~puscule dans la flkche es. A dispersal index was developed to describe seasonal moveterminale et sur les flkches latkrales, puis les charangons se ment. Weevils did not move far throughout the season. Overall 9 1 m t v m la base de et dans la liti& des t e m g r a m dispersal index for both males and females was less than 0.24 m, ClevCes du milieu de 1' CtC. Plus tard dans le courant de la saison, suggesting that on average, weevils do not move further than the les charanqons s'alimentent vers le milieu de la matinCe dans la adjacent tree throughout the season after mating and oviposition.flbche et sur le dessous des branches latkrales. Un indice de dispersion a Ct C ClaborC pour dCcrire les dCplacements saisonniers. Key words: Dispersal, pest management, Pissodes strobi, resis-L'indice global de dispersion pour les mgles et les femelles a Ct C tance, silviculture, white spruce de moins de 0.24 m, laissant ...
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 (Iˆle Perraultcharanc¸on 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 · 10 8 (soil application) and 1.0 · 10 9 conidia/ml (branch application). The results demonstrate for the first time that B. bassiana is an effective entomopathogen against P. strobi.
Controlled mating experiments in the white pine weevil (Pissodes strobi [Peck]) indicated that female weevils either stored sperm or fertilized eggs from one season to the next, and were able to colonize Sitka spruce (Picea sitchensis [Bong.] Carr.) trees without additional mating events. This was interpreted as being beneficial for the insect, in that population establishment in a new habitat could be initiated by dispersing previously mated females without participation of the male. This makes colonization and population/outbreak development more likely as it reduces the need for mate searching in the second season. Paternity identification, based on microsatellite molecular markers, established that the progeny produced in year 2 by females mated only in year 1, were often fathered by more than one male. Multiple paternity, coupled with a lack of parthenogenesis, which was also demonstrated herein, may help to account for the high degree of genetic diversity evidenced in this species.
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