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Postfire salvage logging is used to reduce economic losses; however, burned trees are rapidly colonized by wood-boring insects, which reduce the merchantable value of the wood. This study aims to predict wood borer (Monochamus Megerle in Dejean, 1821) attacks after wildfire as a function of rapidly available variables such as tree basal area, stem diameter, and burn severity using the differenced normalized burn ratio (dNBR). In 2011, we sampled 60 black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) or jack pine (Pinus banksiana Lamb.) plots in five burns from 2010 in the Haute-Mauricie region of Quebec, Canada. A 50 cm bole section was debarked on seven trees in each plot to estimate wood borer attack density. Wood borer attacks were more abundant in black spruce than in jack pine. As a continuous variable, dNBR unveiled a quadratic effect of burn severity on attack density in black spruce, which was higher at moderate burn severity. In jack pine, the highest levels of attack density were found at high burn severity. Models produced in this article will help forest managers to better prioritize areas for salvage logging and thus reduce economic losses due to wood borer activity. Key words: Monochamus, wildfire, salvage logging, wormhole, boreal forest. La coupe de recuperation est utilisee pour reduire les pertes economiques apres un feu de foret. Cependant, les arbres brules sont rapidement colonises par des insectes xylophages, ce qui reduit la valeur marchande du bois. L'objectif de cette etude consistait a predire la densite des attaques de xylophages (Monochamus Megerle dans Dejean, 1821) apres feu, en fonction de variables rapidement disponibles, soit la surface terriere par essence, le diametre de la tige et la severite du feu, a l'aide du << differenced normalized burn ratio (dNBR) >>. En 2011, nous avons echantillonne 60 sites d'epinette noire (Picea mariana (Mill.) Britton, Sterns et Poggenb.) et de pin gris (Pinus banksiana Lamb.) dans cinq brulis de 2010, en Haute-Mauricie au Quebec, Canada. Sur sept arbres par site, une section de tronc de 50 cm fut ecorcee afin d'estimer la densite des attaques de xylophages. Les attaques de xylophages etaient plus abondantes sur l'epinette noire que sur le pin gris. L'utilisation du dNBR en tant que variable continue a revele un effet quadratique de la severite du feu sur la densite des attaques sur l'epinette noire, qui etait plus elevee apres un feu de severite moderee. Dans le pin gris, la densite maximale des attaques de xylophages etait associee a un feu de severite elevee. Les modeles produits dans cet article aideront les amenagistes forestiers a mieux prioriser les secteurs pour des coupes de recuperation et ainsi reduire les pertes economiques dues aux activites des insectes xylophages. Mots-cles: Monochamus, feu de foret, coupe de recuperation, trous de vers, foret boreale., Introduction Large wildfires generate tremendous numbers of dead trees, which are increasingly salvaged to reduce economic losses resulting from this natural disturbance (Lindenmayer et al. 2008). However, most postfire stands [...]

Establishing feeding sites is critical for the survival of neonate Lepidoptera larvae. Rapid foliar quality changes during leaf expansion create a narrow window of opportunity for establishment of early-spring feeders. We examined the effect of phenological synchrony between black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) and balsam fir (Abies balsamea (L.) Mill.) budbreak and spruce budworm (Choristoneura fumiferana (Clemens)) emergence on the feeding behaviour of young larvae and on overall larval growth and survival under laboratory conditions. We correlated these variables with bud development and foliar toughness during the growing season. Our results show that early-emerging second-instar larvae were unable to feed on either black spruce or balsam fir buds; budworm on balsam fir mined old foliage and exhibited good survival and performance, but those on black spruce remained on the foliar surface and suffered high mortality and low growth. In the second later-emerging cohort, bud feeding gradually increased on black spruce whereas it was already the predominant behaviour on balsam fir, and no differences in performance were observed between host species. Thus, black spruce budbreak constitutes a strict window of opportunity, since larvae are often unable to mine the old foliage. Our results suggest that mechanical toughness could be the obstacle preventing young larvae from mining old black spruce needles. Our findings confirm the importance of second-instar ecology in spruce budworm, suggesting that, if climate warming eventually results in an improvement in phenological synchrony between spruce budworm and black spruce, larval survival may increase. Key words: second instar larvae, window of opportunity, foliar toughness, spruce budworm, black spruce. Pour survivre, les jeunes larves de lepidopteres doivent trouver des sites d'alimentation. La qualite des feuilles change rapidement durant leur expansion ce qui laisse une etroite fenetre d'opportunite pour l'etablissement des larves qui se nourrissent tot au printemps. Nous avons etudie l'effet de la synchronisation phenologique entre le debourrement de l'epinette noire (Picea mariana (Mill.) Britton, Sterns & Poggenb.) et du sapin baumier (Abies balsamea (L.) Mill.) d'une part et l'emergence de la tordeuse des bourgeons de l'epinette (Choristoneura fumiferana (Clemens) d'autre part, sur le comportement alimentaire des jeunes larves ainsi que globalement sur la survie et la croissance des larves dans des conditions de laboratoire. Nous avons correle ces variables avec le developpement des bourgeons et la coriacite des aiguilles durant la saison de croissance. Nos resultats montrent que les larves du deuxieme stade qui emergent tot etaient incapables de se nourrir des bourgeons de l'epinette noire ou du sapin baumier. Sur le sapin baumier, la tordeuse des bourgeons forait dans les vieilles aiguilles et avait un bon taux de survie et une bonne performance. Par contre sur l'epinette noire la tordeuse des bourgeons demeurait a la surface des aiguilles et avait un taux eleve de mortalite et une faible croissance. Dans le cas de la deuxieme cohorte qui emergeait plus tard, la consommation de bourgeons a graduellement augmente sur l'epinette noire tandis que c'etait deja le comportement predominant sur le sapin baumier et aucune difference de performance n'a ete observee entre les especes hotes. Par consequent, le debourrement de l'epinette noire constitue une etroite fenetre d'opportunite etant donne que les larves sont souvent incapables de forer dans les vieilles aiguilles. Nos resultats indiquent que la coriacite mecanique pourrait etre un obstacle qui empeche les jeunes larves de forer dans les vieilles aiguilles de l'epinette noire. Nos resultats confirment l'importance de l'ecologie du deuxieme stade larvaire de la tordeuse des bourgeons de l'epinette, ce qui indique que si le rechauffement du climat entraine eventuellement une amelioration de la synchronisation phenologique entre la tordeuse des bourgeons de l'epinette et l'epinette noire, la survie des larves pourrait augmenter. [Traduit par la Redaction] Mots-cles: deuxieme stade larvaire, fenetre d'opportunite, coriacite des aiguilles, tordeuse des bourgeons de l'epinette, epinette noire., Introduction Shifts in phenology under a changing climate may alter the dynamics of species interactions, leading to dramatic changes in population sizes (Boggs 2016). One important example, which can have [...]

We examine the extent to which foliar monoterpenes are trapped in the epicuticular waxes as part of an investigation into their role in natural defense against folivores. We monitored concentrations in white spruce (Picea glauca (Moench) Voss) previous-year foliage and expanding foliage and their epicuticular waxes over the 2010 (14 trees) and 2011 (25 trees) growing seasons. In 2010, concentrations were low in the spring and increased over the summer; in 2011, they stayed low. The monoterpene profile of individual trees was similar between years and showed a consistent pattern over the growing season; in expanding foliage, δ-3-carene was only present in spring, whereas bornyl acetate increased over the growing season. Individual wax monoterpene profiles correlated with those of foliage, but the total concentration showed a different phenological pattern. Total content remained constant throughout the growing season on previous-year foliage but decreased on expanding foliage. Electron microscopy suggests this is due to changes in stomatal wax plugs and their role in blocking evaporation from the stomata. These findings suggest that insects contacting the leaf surface will receive accurate information from the wax chemical composition about the monoterpene mix but not about overall monoterpene levels. Key words: Picea glauca, leaf surface, terpenoids, natural resistance. Cette etude examine la retention des monoterpenes dans la cire epicuticulaire afin de mieux comprendre leur role dans la defense naturelle contre les insectes folivores. Nous avons suivi les concentrations de monoterpenes dans le feuillage et la cire epicuticulaire de l'epinette blanche (Picea glauca (Moench) Voss) durant les saisons de croissance 2010 (14 arbres) et 2011 (25 arbres) en echantillonnat les aiguilles de l'annee precedente et celles en expansion. En 2010, les concentrations etaient basses au printemps et ont augmente durant l'ete; en 2011 elles sont demeurees basses. Le profil des monoterpenes de chaque arbre etait semblable d'une annee a l'autre, ainsi que sa progression phenologique: dans le feuillage en expansion, le δ-3-carene etait present seulement au printemps, tandis que l'acetate de bornyle augmentait au cours de la saison. Les concentrations relatives des monoterpenes dans la cire etaient correlees avec celles du feuillage, mais la phenologie de la teneur totale etait differente : elle demeurait constante durant la saison de croissance sur le feuillage de l'annee precedente mais diminuait sur le feuillage en expansion. La microscopie electronique suggere que cela est du a l'erosion des bouchons de cire qui bloquent l'evaporation par les stomates. Ces resultats indiquent que les insectes qui viennent en contact avec la surface des feuilles percoivent correctement les concentrations relatives de monoterpenes mais non la teneur totale. Mots-cles: Picea glauca, surface foliaire, terpenoides, resistance naturelle., Introduction Terpenoids are key players in the defense systems of conifers, and many species produce a broad diversity of terpenoid products. Variation in monoterpene content occurs between environments (e.g., it [...]

This study aimed to characterize the vertical distribution of longhorned beetle larvae in burned trees of the eastern Canadian boreal forest. Black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) and jack pine (Pinus banksiana Lamb.) trees burned at three severity levels were cut, and 30 cm boles were collected from the ground up to a height of 9.45 m. Boles were debarked and dissected to collect insect larvae. Results show that the three most abundant longhorned beetle species were vertically segregated among burned jack pine and black spruce trees, but the section having the highest timber value was heavily infested by woodborer larvae. Larval density distribution of Monochamus scutellatus scutellatus (Say) and of Acmaeops proteus proteus (Kirby) could be linked with bark thickness, which also depends on fire severity. Lightly burned stands of black spruce were the most heavily infested and should be salvaged only if they are easily accessible and can thus be rapidly harvested and processed at the mill. More severely burned stands should be salvaged later as they will be less affected by woodborers, as should jack pine, which is lightly infested compared with black spruce. The ecological role of stumps should be further investigated because they could still have an ecological value after salvage logging as Arhopalus foveicollis (Haldeman) uses them specifically. Key words: Cerambycidae, vertical distribution, boreal forest, bark thickness, fire severity. Cette etude visait a caracteriser la repartition verticale des larves de longicornes dans des arbres brules de la foret boreale de l'est du Canada. Des epinettes noires (Picea mariana (Mill.) Britton, Sterns & Poggenb.) et des pins gris (Pinus banksiana Lamb.) brules atrois degres de severite ontete coupes etdesbuches de 30cmontete recoltees, apartirdu soljusqu'aune hauteur de 9.45 m. Les buches ont ete ecorcees et dissequees pour recolter les larves d'insectes. Les resultats revelent que les trois especes les plus abondantes de longicornes montraient une segregation verticale sur le pin gris et l'epinette noire brules, mais que la section ayant la plus grande valeur commerciale etait fortement infestee par des larves de longicorne. La densite larvaire de Monochamus scutellatus scutellatus (Say) et celle d'Acmaeops proteus proteus (Kirby) pourraient etre liees a l'epaisseur de l'ecorce, qui depend elle aussi de la severite du feu. Les peuplements d'epinette noire legerement brules etaient les plus infestes et devraient etre recuperes seulement s'ils sont faciles d'acces et peuvent ainsi etre rapidement recuperes et traites a l'usine. Les peuplements plus gravement brules devraient etre recuperes plus tard, car ils sont moins affectes par les longicornes, de meme que le pin gris qui est moins infeste que l'epinette noire. Le role ecologique des souches devrait etre etudie davantage car elles pourraient conserver une valeur ecologique meme apres la coupe de recuperation puisque Arhopalus foveicollis (Haldeman) les utilisent specifiquement. Mots-cles: Cerambycidae, repartition verticale, foret boreale, epaisseur de l'ecorce, severite du feu., Introduction Wildfire is considered a dominant natural disturbance in the Canadian boreal forest (Nappi et al. 2011). Between 2000 and 2010, an average of 1784 590 ha of forest has [...]

Thinning has frequently been recommended for reducing damage caused by spruce budworm (Choristoneura fu-miferana (Clemens)). It is believed that this technique enhances the mechanisms of resistance of trees (antibiosis and tolerance) to this insect. However, various research projects that have focused upon effects of this silvicultural tool on host tree resistance have yielded equivocal results. A better understanding of the effects of this technique on host tree resistance and budworm performance can help us to reduce the impact of this insect while respecting the ecological integrity of the forests. We examined the effects of stand commercial thinning and drainage class on balsam fir (Abies balsamea (L.) Mill.)), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) resistance to spruce budworm 3 years after thinning. We wanted to determine if this technique could be used as preventive tool against insect defoliators. Field-rearing experiments of spruce budworm were conducted, together with foliar chemical analyses, along a gradient of stand thinning intensity (0% (control), 25% (light), and 40% (heavy)) and drainage class (rapidly drained, class 2; mesic with seepage, class 3; subhygric, class 4; and hydric, class 5). Despite having favoured budworm performance (high pupal mass) and winter survival, heavy thinning increased balsam fir and white spruce tolerance (amount of current-year foliage remaining) to a level that resulted in overall increased host tree resistance to the insect. This response was caused by strong foliage production in reaction to the thinning treatment. Light thinning did not increase host tolerance, except in balsam fir and white spruce that were growing on hydric and subhygric sites, respectively, demonstrating the importance of this variable in determining host tree resistance. These results suggest that heavy thinning may be used as a preventive measure during the low-density phase of budworm populations, since this technique increased foliar production in balsam fir and white spruce, rendering them more resistant to attack by this insect. Resume: L'eclaircie a ete souvent recommandee pour reduire les dommages causes par la tordeuse des bourgeons de l'epinette (Choristoneura fumiferana (Clemens)). On croit que cette technique ameliore les mecanismes de resistance des arbres (antibiose et tolerance) a la tordeuse des bourgeons de l'epinette. Cependant, les resultats rapportes par les nombreuses etudes effectuees sur le sujet sont contradictoires. Une meilleure comprehension de l'effet de l'eclaircie sur la resistance des arbres et la performance de la tordeuse des bourgeons de l'epinette peut nous aider a reduire l'impact de ce ravageur tout en respectant l'integrite ecologique de la foret. Cette etude se penche sur l'effet de l'eclaircie commerciale et de la classe de drainage de la station sur la resistance du sapin baumier (Abies balsamea (L.) Mill.), de l'epinette blanche (Picea glauca (Moench) Voss) et de l'epinette noire (Picea mariana (Mill.) Britton, Sterns & Poggenb.) a la tordeuse des bourgeons de l'epinette trois ans apres l'application de l'eclaircie pour determiner si l'on peut utiliser cet outil sylvicole comme mesure preventive. Des elevages de tordeuse des bourgeons de l'epinette sur le terrain et des analyses chimiques foliaires des essences hotes ont ete effectues en fonction d'un gradient d'eclaircie (0% (temoin), 25% (legere) et 40% (forte)) et de classe de drainage de la station (drainage rapide, classe 2; mesique avec drainage lateral, classe 3; subhygrique, classe 4; et hydrique, classe 5) dans la sapiniere a bouleau blanc. L'eclaircie forte a ameliore la performance (poids des chrysalides) et la survie hivernale de la tordeuse des bourgeons de l'epinette. Par contre l'eclaircie forte a accru la tolerance (quantite de feuillage residuel) du sapin baumier et de l'epinette blanche assez pour entrainer une augmentation de la resistance globale a l'insecte. Cette augmentation de resistance resulte d'une forte production de feuillage en reaction au traitement effectue trois ans auparavant. L'eclaircie legere n'a pas accru la resistance des arbres hotes, sauf chez les tiges de sapin baumier et d'epinette blanche croissant respectivement dans les stations hydriques et subhygriques, demontrant ainsi l'importance de l'effet de cette variable sur la resistance des arbres hotes. Ces resultats indiquent que l'eclaircie forte pourrait etre utilisee comme mesure de lutte preventive pendant la phase endemique des populations de tordeuse des bourgeons de l'epinette car ce traitement a augmente la production de feuillage chez le sapin baumier et l'epinette blanche, ce qui les rend plus resistants aux attaques de ce ravageur., Introduction Outbreaks of spruce budworm (Choristoneura fumiferana (Clemens)) occur throughout North America's maritime and boreal forests and usually last 5 and 20 years at the local and regional scale, respectively. [...]

Monoterpenes, source of the distinctive odor of conifers, are generally considered plant defensive compounds. However, they are also known to act as long-range insect attractants, as they are volatile and permeate forest airspaces. Moreover, they are lipid soluble and can be absorbed into plant epicuticular waxes. We test their role in short-range host plant choice by both adult females and larvae of a folivorous forest pest ( Choristoneura fumiferana). We conducted laboratory assays testing the responses of Eastern spruce budworm to an artificial monoterpene mix (α-pinene, β-pinene, limonene, myrcene) and to white spruce ( Picea glauca) epicuticular waxes in closed arenas. Ovipositing females preferred filter paper discs treated with P. glauca waxes to controls, and preferred the waxes + monoterpenes treatment to waxes alone. However, females showed no preference between the monoterpene-treated disc and the control when presented without waxes. Feeding larvae prefered wax discs to control discs. They also consumed discs treated with realistic monoterpene concentrations and wax preferentially over wax-only discs, but showed no preference between extremely high monoterpene concentrations and wax-only controls. In an insect-free assay, P. glauca epicuticular wax decreased monoterpene volatilization. These results suggest that P. glauca waxes and realistic concentrations of monoterpenes are stimulatory to both egg-laying females and feeding larvae, and that their effects are synergistic. [ABSTRACT FROM AUTHOR]

Twig beetles in the genus Pityophthorus Eichhoff, 1864 include more than 300 species worldwide, with maximum diversity in tropical and subtropical regions. To date, approximately 50 species of Pityophthorus have been recorded in Canada, and these species are associated mainly with coniferous trees. Since 1981, no comprehensive study on this difficult taxonomic group has been conducted in Quebec, Canada, most likely due to their limited significance as forest pests. Based on data gathered from five years of field sampling in conifer seed orchards and compiled from various entomological collections, the distribution of Pityophthorus species in Quebec is presented. Approximately 291 new localities were recorded for the Pityophthorus species. Five species-group taxa, namely P. puberulus (LeConte, 1868), P. pulchellus pulchellus Eichhoff, 1869, P. pulicarius (Zimmermann, 1868), P. nitidus Swaine, 1917, and P. cariniceps LeConte&Horn, 1876 were the most widespread. In contrast, P. consimilis LeConte, 1878, P. intextus Swaine, 1917, P. dentifrons Blackman, 1922, P. ramiperda Swaine, 1917, and P. concavus Blackman, 1928 display a notably limited distribution. In addition, the first distribution records of P. intextus and P. biovalis Blackman, 1922 are furnished, and the subspecies P. murrayanae murrayanae Blackman, 1922 is reported from Quebec for the second time. Moreover, distribution maps are provided for all Pityophthorus species recorded in the province of Quebec. [ABSTRACT FROM AUTHOR]

The pattern of feeding of Eastern spruce budworm Choristoneura fumiferana (Clem.) (Lepidoptera, Tortricidae) is compared on foliage from white spruce Picea glauca (Moench) Voss. (Pinaceae) trees previously determined to be susceptible and resistant to defoliation by budworm. No differences are observed in electrophysiological responses from taste sensilla to aqueous extracts of the two foliage types, nor is there a preference for either extract type in a choice test. Acetone extracts from the two foliage types are both preferred to a control sucrose solution, although neither elicits a preference relative to the other. These results suggest that there is no difference in phagostimulatory power of internal leaf contents of the two foliage types. Longer-term observation of feeding behaviour in a no-choice situation shows no difference in meal duration, confirming the lack of difference in phagostimulatory power. However, on average, intermeal intervals are twice as long on the resistant foliage, leading to an overall lower food consumption during the assay. This result suggests an anti-digestive or toxic effect of the resistant foliage that slows behaviour and limits food intake. Previous research has shown that waxes of the resistant foliage deter initiation of feeding by the spruce budworm and that this foliage contains higher levels of tannins and monoterpenes. The data suggest that the resistant foliage contains a post-ingestive second line of defence against the spruce budworm. [ABSTRACT FROM AUTHOR]

The article examines the effects of tebufenozide on the diapause of eastern spruce budworm by conducting laboratory experiments on budworm's first-instar larvae treated with tebufenozide dissolved in acetone. Larvae exposed to small dose of tebufenozide displayed precocious moulting in the second instar, effectively disrupting diapause while those exposed to larger doses induced moulting in first instars. Findings suggests that diapause disruption by tebufenozide may be an alternative strategy in controlling eastern spruce budworm.

The hemlock looper [Lambdina fiscellaria (Guenée)], a widespread and highly polyphagous Geometridae, is considered one of the most economically important defoliators of North American coniferous forests. Variations in the number of larval instars between geographic populations of this species have been previously reported in the literature. However, whether such developmental polymorphism occurs within a given population is unknown. In this study, we report the presence of both four and five larval instar individuals within a population of hemlock looper in Newfoundland when reared on balsam fir. For both sexes, the majority of individuals reared on balsam fir shoots went through four larval instars, but more than one third of the females (35.3%) went through five larval instars. Females with four larval instars developed faster and had smaller pupal weight than females with five larval instars. However, a growth-related index (weight gain per unit of time) was similar for the two ecotypes (four or five larval instars). No significant difference was observed between the two ecotypes in terms of reproductive capacity (fecundity and egg size). We also found significant differences in life history traits between males and females. Results indicate that developmental polymorphism, in this case, the variation in the number of larval instars, might provide some adaptive attributes that allowed exploitation of a broader ecological niche. [ABSTRACT FROM AUTHOR]

The effect of the type of diet consumed on the reproduction of Podisus nigrispinus (Dallas) was studied. Females of P. nigrispinus fed on an artificial diet had a longer preoviposition period than those fed on 3rd or 5th instar cotton leafworm larvae [Alabama argillacea (Hübner)] or mealworm (Tenebrio molitor L.) larvae. P. nigrispinus females fed on 3rd or 5th instar cotton leafworm larvae or mealworm larvae had a longer oviposition period than females on an artificial diet. The numbers of egg masses per female and of egg masses per female per day were higher when P. nigrispinus was fed on 3rd or 5th instar cotton leafworm larvae than when fed on an artificial diet. Podisus nigrispinus females fed on 5th instar cotton leafworm larvae produced a greater number of eggs per female, eggs per egg mass, and eggs per female per day, had a higher nymphal hatch rate than those fed other diets and had higher numbers of oocytes per central ovariole or per ovary than those fed on 3rd instar cotton leafworm larvae, artificial diet, house fly (Musca domestica L.) larvae or mealworm larvae. [ABSTRACT FROM AUTHOR]