Richard Berthiaume

Exergetic evaluation of the renewability of a biofuel

Abstract A method is described to quantify the renewability of a biofuel, namely ethanol produced from corn. In the presentation, the ideal CO2–glucose–ethanol cycle is considered to show that exergy can be potentially produced through the harnessing of natural thermochemical cycles. Then exergy accounting is used to evaluate the departure from ideal behavior caused by non-renewable resource consumption through the concept of restoration work. This procedure leads the authors to propose a renewability indicator. The different cycles and processes involved in ethanol production from corn are described. Based on the renewability indicator calculated for the overall process, for the conditions prevailing in Quebec, Canada, ethanol production is seen to be not renewable.

Effects of food nutritive quality and Bacillus thuringiensis onfeeding behaviour, food utilization and larval growth of spruce budworm Choristoneura fumiferana (Clem.) when exposed as fourth‐ and sixth‐instar larvae

Abstract 1 Feeding behaviours, and lethal and sublethal (growth, development and food utilization) effects of Foray 48B, a commercial formulation of Bacillus thuringiensis (kurstaki), were investigated on fourth‐ and sixth‐instar spruce budworm larvae according to food nutritive quality. Nitrogen and soluble sugar content of artificial diets were modified to obtain three different qualities of food, simulating variations in nutritive quality of host tree.

Effect of temperature and host tree on cold hardiness of hemlock looper eggs along a latitudinal gradient.

The hemlock looper, Lambdina fiscellaria, is an economically important insect pest of Canadian forests which overwinters as eggs. Although the hemlock looper causes extensive damages, no information on the mechanisms related to its cold tolerance is known. The objective of this study was to determine the effect of temperature and exposure duration on hemlock looper winter survival but also to identify seasonal supercooling capacity and cryoprotectant levels of three populations along a latitudinal gradient. As host plant may contribute to offspring overwintering success, cold tolerance of hemlock looper eggs from parents whose larvae were fed on three different tree species was also measured. Mean supercooling point (SCP) of hemlock looper eggs was lower than -30 °C from October through the following spring with values being as low as -47 °C in February. Trehalose was the most abundant sugar found in hemlock looper eggs with a peak concentration of 0.3 μg mg⁻¹ DW⁻¹. Glycerol, a polyol, was more often absent in eggs of the different populations and tree species tested in the study. When exposed to different temperature regimes for various periods of time, significant mortality of hemlock looper eggs occurred at higher temperatures than the mean SCP. Thus, hemlock looper could be considered as a chill tolerant species. No clear pattern of population and host plant effects on SCP and cryoprotectants was detected in this study. However, when exposed to different winter temperatures and exposure duration, hemlock looper from higher latitudes survived better (survival rates ranging between 0 and 89% at -20 °C) than those from lower latitudes (survival rates ranging between 0 and 56% at -20 °C). Our results may contribute to a better understanding of hemlock looper winter biology and thus facilitate predictions of outbreaks and range expansion.

Wood losses and economical threshold of Btk aerial spray operation against spruce budworm

BACKGROUND Spruce budworm, Choristoneura fumiferana (Clem.), causes cumulative defoliation and hence annual growth loss of the balsam fir, Abies balsamea (L.) Mill, host tree. Annual growth increments of mixed balsam fir stands were measured by stem analysis over a 9 year period (1994-2002), when Bacillus thuringiensis ssp. kurstaki (Btk) was applied to control spruce budworm defoliation. With this approach, it was possible to quantify the change in stand volume growth after aerial spray applications of Btk. RESULTS Differences between the periodic volume increment of protected and unprotected plots were statistically significant, while differences between protected and budworm-free plots were not significant. After 9 years, the difference in periodic increment between protected and unprotected plots was 20 m(3) ha(-1), and the difference in periodic mortality was 20.5 m(3) ha(-1). CONCLUSION An economic assessment of Btk treatments indicates that biopesticide aerial spraying operations are justified, as they prevented substantial balsam fir mortality and growth losses over the 9 year study.

Developmental Polymorphism in a Newfoundland Population of the Hemlock Looper, Lambdina fiscellaria (Lepidoptera: Geometridae)

Abstract 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.

Comparative Use of Mindarus abietinus (Homoptera: Aphididae) by Two Coccinellids (Coleoptera: Coccinellidae), the Native Anatis mali and the Exotic Harmonia axyridis, in a Christmas Tree Plantation

Abstract The exotic coccinellid Harmonia axyridis (Pallas) recently expanded its range into eastern Canada and elsewhere in North America. We hypothesized that this coccinellid should be less well adapted to the prey Mindarus abietinus Koch. on balsam fir trees than the native coccinellid Anatis mali (Say), which evolved in close association with aphids on conifers in North America. We compared, under field conditions, prey use by both species by collecting data on their synchrony with M. abietinus, their prey searching and predation behaviors, life stage distribution in fir canopy, and their overall reproductive success in this system. The seasonal life cycle of A. mali was better synchronized with that of M. abietinus compared with that of H. axyridis. In spring, A. mali adults appeared nearly 2 wk earlier on trees than H. axyridis and were active predators of the aphid fundatrices. A. mali oviposition thus began before the aphid population started to grow, and its larvae were most active during peak aphid colonies. Behavioral observations showed that both adults and larvae of the native A. mali searched for prey more actively than those of H. axyridis. Distribution of life stages also showed that eggs and pupae had different distributions on trees and that the adult-to-adult net reproductive rate of A. mali was three times higher than that of H. axyridis. Thus, the native A. mali was better adapted than H. axyridis to prey on M. abietinus, possibly because it evolved for a much longer period of time with this prey in conifer habitats.

Influence of balsam fir (Abies balsamea) budburst phenology on hemlock looper (Lambdina fiscellaria)

Many herbivorous insects emerge synchronously with budburst of their host plant, as the nutritional quality of foliage often decreases rapidly following budburst. We carried out manipulative field experiments to evaluate the influence of bud and shoot phenology on performance of the hemlock looper, Lambdina fiscellaria Guenée (Lepidoptera: Geometridae: Ourapterygini), on balsam fir, Abies balsamea (L.) Mill. (Pinaceae), in NF, Canada. Hemlock looper survival, pupal weight, and realized fecundity, which were then combined to estimate fitness, were all highest when newly emerged first instars were placed on foliage of current‐year shoots that had completed approximately 25–35% of their elongation, and lower when placed on younger or older foliage. Survival of a small portion of larvae placed on buds a week before budburst suggests that newly emerged first instars either entered unburst buds or survived for a week without food. In laboratory experiments, approximately half of larvae survived for 4 days without food or water at 10 °C and 65% r.h. The timing of egg hatch in the field appeared to be adaptive, but the short duration of egg hatch suggests that another factor in addition to host plant phenology exerts stabilizing selection pressure on the timing of egg hatch.

Influence of Partial Cutting on Parasitism of Endemic Spruce Budworm (Lepidoptera: Tortricidae) Populations

ABSTRACT Silvicultural treatments such as thinning have been suggested as management tools against the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae). Among other things, parasitoids are also proposed to be influenced by silvicultural procedures, but the effect of thinning on spruce budworms natural enemies has not been tested yet. In this study, the influence of partial cutting on parasitism of endemic spruce budworm populations has been investigated in mature balsam fir-white birch forests. Two intensities of partial cutting (25 and 40% stand basal area reduced) were conducted in 2009 and parasitism of introduced spruce budworm larvae and pupae was determined during the 3 yr after these treatments. Pupal parasitism was too low for comparison between treatments. However, 2 yr after treatments, parasitism of the fourth- and fifth-instar larvae was significantly reduced in plots with both intensities of partial cutting, which was attributed to the parasitoid Tranosema rostrale (Brischke). Three years after treatments, no significant influence of partial cutting on parasitism of spruce budworm larvae was found. This study suggests that the influence of partial cutting on parasitism of endemic spruce budworm populations is not consistent, but that under certain circumstances parasitism is reduced by partial cutting.

Effect of Temperature and Tree Species on Damage Progression Caused by Whitespotted Sawyer (Coleoptera: Cerambycidae) Larvae in Recently Burned Logs

ABSTRACT The whitespotted sawyer, Monochamus scutellatus scutellatus (Say) (Coleoptera: Cerambycidae), is one of the most damaging wood-boring insects in recently burned boreal forests of North America. In Canada, salvage logging after wildfire contributes to maintaining the timber volume required by the forest industry, but larvae of this insect cause significant damage that reduces the economic value of lumber products. This study aimed to estimate damage progression as a function of temperature in recently burned black spruce (Picea mariana (Miller) Britton, Sterns, and Poggenburg) and jack pine (Pinus banksiana Lambert) trees. Using axial tomographic technology, we modeled subcortical development and gallery depth progression rates as functions of temperature for both tree species. Generally, these rates were slightly faster in black spruce than in jack pine logs. Eggs laid on logs kept at 12°C did not hatch or larvae were unable to establish themselves under the bark because no larval development was observed. At 16°C, larvae stayed under the bark for >200 d before penetrating into the sapwood. At 20°C, half of the larvae entered the sapwood after 30–50 d, but gallery depth progression stopped for ≈70 d, suggesting that larvae went into diapause. The other half of the larvae entered the sapwood only after 100–200 d. At 24 and 28°C, larvae entered the sapwood after 26–27 and 21 d, respectively. At 28°C, gallery depth progressed at a rate of 1.44 mm/d. Temperature threshold for subcortical development was slightly lower in black spruce (12.9°C) than in jack pine (14.6°C) and it was 1°C warmer for gallery depth progression for both tree species. These results indicate that significant damage may occur within a few months after fire during warm summers, particularly in black spruce, which highlights the importance of beginning postfire salvage logging as soon as possible to reduce economic losses.

Host Tree Species and Burn Treatment as Determinants of Preference and Suitability for Monochamus scutellatus scutellatus (Coleoptera: Cerambycidae)

ABSTRACT After fire, the whitespotted sawyer, Monochamus scutellatus scutellatus (Say) (Coleoptera: Cerambycidae), is considered one of the most damaging xylophagous insects by forest industries in the eastern boreal forest of North America. Although this species is often considered opportunistic because it dwells on various stressed host trees, it can be found in very high abundance after forest fire and, consequently, it has been suspected of being a pyrophilous species or fireassociated species. The aim of this study was first to determine whether the whitespotted sawyer lays eggs preferentially on burned rather than unburned hosts, and second, to determine its preference between black spruce (Picea mariana [Mill] B.S.P.) and jack pine (Pinus banksiana Lamb.) for oviposition. Host suitability also was estimated to determine if whitespotted sawyer females make optimal choices to maximize offspring development. To determine host suitability, we used the abundance distribution of larval instars as a proxy of larval development quickness and we compared weight and head-capsule width of larvae of different larval instars as measures of insect growth in each type of log. Based on the frequency of oviposition behavior, females showed no preference for either burned or unburned black spruce logs, and both were equally suitable for larval development. Furthermore, females laid more eggs on black spruce than on jack pine, but host suitability was not statistically affected. Nevertheless, larvae had mostly reached the fourth instar on black spruce, whereas those on jack pine were mostly at the third instar, suggesting faster development on black spruce.