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The rate of insect invasions continues to accelerate, driven by global trade, climate change, and land use modification. Self-sustaining “public interest” tools such as importation biological control can be powerful ways to mitigate the impacts of insect invasions. However, these interventions can fall prey to counterproductive risk-averse attitudes if their risks are not balanced with the consequences of inaction. Failing to intervene can incur opportunity costs and allow the direct and indirect negative effects of invasive species to accumulate over time. Here, we argue for the explicit consideration of both risks and benefits, expressed in a broad range of currencies, for existing and emerging self-sustaining interventions such as biological control and genetic interventions. An appropriate level of focus on not only the risks of interventions, but also on the multi-faceted risks of inaction, could help to encourage responsible implementation of invasive insect management.

Major depressive disorder (MDD) is the leading cause of disability worldwide. Of individuals with MDD, 30% to 50% are unresponsive to common antidepressants, highlighting untapped causal biological mechanisms. Dysfunction in the microbiota-gut-brain axis has been implicated in MDD pathogenesis. Exposure to chronic stress disrupts blood-brain barrier integrity; still, little is known about intestinal barrier function in these conditions, particularly for the small intestine, where absorption of most foods and drugs takes place.

To determine the factors leading to outbreaks of the sugarcane aphid, Melanaphis sacchari,(Zehntner) (Hemiptera: Aphididae) in sorghum in Haiti, a survey was carried out on farms during two cropping seasons, spring and fall of 2018. A total of 45 plots in three Haitian regions were monitored from the five-leaf stage to grain ripening. Infestation with M. sacchariwas significantly higher in spring than in fall, except in one location. Melanaphis saccharipopulations varied significantly according to phenological stages of sorghum, with significantly higher abundance during the heading and flowering stages than other stages. In and around sorghum fields, the sugarcane aphid was observed on plants from three families: Poaceae, Malvaceae, and Cucurbitaceae. Aphid natural enemies found in sorghum fields consisted of eight species of ladybeetles (Coleoptera: Coccinellidae), one hoverfly (Diptera: Syrphidae), one lacewing (Neuroptera: Chrysopidae), and one predatory midge (Diptera: Cecidomyiidae). In addition to these predators, two parasitoid species, Adialytussp. (Hymenoptera: Braconidae) and Pachyneuron aphidis(Bouché) (Hymenoptera: Pteromalidae), emerged from sugarcane aphid mummies. Predator and parasitoid densities were highly affected by growing season, with most of the biological control happening in fall. This study provides insights on sugarcane aphid management in Haiti and the Caribbean Islands.

AbstractThe sterile insect technique is a new approach for the integrated management of Drosophila suzukiiMatsumura (Diptera: Drosophilidae), an invasive pest in North America. We evaluated, under laboratory conditions, the mating capacities and success of male D. suzukii, irradiated at a dose of 120 Gy, with and without competition. We also explored the tendency of females to remate depending if their first mate was irradiated or not. We observed that irradiated males have the same mating capacity as control males, copulating with, respectively, 6.4 ± 1.9 females versus 6.9 ± 2.0 females in a 24-hour period. Irradiated males won the competition 37.5% of times, which is not significantly different from competiveness of control males. Female remating can be considered infrequent and not significantly influenced by male treatment: 7.4% of the females first mated with control males and 18.8% of the females first mated with irradiated males remated when given the opportunity two days and four days after the first mating. Latency before mating and mating duration were not significantly influenced by male treatment, but by presence of male competition. Overall, irradiated males thus seem to be as performant as control males, which is an important condition for a successful sterile insect technique programme.

AbstractAphidius erviHaliday (Hymenoptera: Braconidae) is a major natural enemy of several agricultural pests in North America. Yet little is known about its overwintering strategy, especially concerning the plastic response to photoperiod and temperature that induce diapause. Information on parasitoid overwintering patterns is of great importance if we aim to predict their phenology and better inform pest outbreak control. Moreover, there is increasing evidence of plastic and genetic changes in overwintering strategies in insect from temperate areas following climate change. We set up a laboratory approach to better understand the factors acting on diapause induction in A. ervi. We studied the diapause incidence in a population from Québec, Canada, using the combination of two temperatures (14 °C and 20 °C) and three photoperiod treatments (10:14, 12:12, 14:10 [light:dark] hours). We found an effect of both factors on diapause incidence; A. erviexpressed close to 95% of diapause at the most fall-like conditions (14 °C, 10:14 [light:dark] hours) and almost no diapause (3.5%) at the most summer-like conditions tested (20 °C, 14:10 [light:dark] hours). This parasitoid species does have the potential to enter diapause in Québec before lethal frosts, despite a recent introduction from France (1960s), where mild winter occurs compared with Québec.

AbstractWe explored ecological aspects of the early establishment of the association between the Japanese beetle, Popillia japonica(Newman) (Coleoptera: Scarabaeidae), and the adult tachinid parasitoid, Istocheta aldrichi(Mesnil) (Diptera: Tachinidae), in the province of Québec, Canada. The Japanese beetle started its invasion in the late 1930s, whereas I. aldrichiwas detected only in 2009. It is assumed that I. aldrichispread in the province from its introduced range in the northeastern United States of America. Throughout the summer, we used baited traps in eight localities of southern Québec (2018–2019) and in 13 raspberry (Rubus idaeus) fields (2022) localised along a latitudinal gradient to describe the distribution and seasonal occurrence of both species and the parasitism rates of I. aldrichi. We also mapped observational data from the online platform iNaturalist to further describe the current distribution of both the host and its parasitoid. Results indicate that I. aldrichiis well spread in southern Québec and along the St. Lawrence River in most areas where the Japanese beetle is present. Parasitism mostly occurs from late June to mid-July, before the peak of Japanese beetle populations, and levels of total seasonal parasitism range from 3.9 to 27.3% across sampled sites. Together, trap captures and data from iNaturalist provide evidence that I. aldrichiis now established in most areas of the province of Québec where the Japanese beetle is present.

AbstractNeorthacheta dissimilisMalloch (Diptera: Scathophagidae) is a poorly known scathophagid fly that feeds and develops on iris (Iridaceae). A survey of its occurrence was performed at the Montréal Botanical Garden (Montréal, Québec, Canada) in 2018, 2019, and 2020. Iris species and cultivars from two subgenera, Irisand Limniris, were evaluated for larval infestation. When pooled for subgenera and years, data from 18 Irisclasses revealed high levels of infestation per flower stalk, ranging from 34% to 100%. When analysed per bud or flower, levels of infestation remained high, ranging from 19% to 100%, but generally was lower than for flower stalks as the unit of replication. The mean number of N. dissimilislarvae per infested flower or bud was higher for the subgenus Limniris(1.13) than for the subgenus Iris(1.03), with a maximum of four N. dissimilislarvae per flower being observed. These figures are worrying for horticulturalists because the insect is prevalent and causes either abortion or aesthetic damages to iris flowers.

AbstractWe studied the diversity and summer seasonal activity-density of Carabidae associated with soybean fields infested by the soybean aphid (Aphis glycinesMatsumura; Hemiptera: Aphididae) in Québec, Canada. Carabid beetles were sampled in six to seven fields from June to September 2004 and 2005 using pitfall traps. A total of 33 species from 15 genera were identified, with the exotic Pterostichus melanarius(Illiger) (Coleoptera: Carabidae), representing 75.8% and 84.5% of all individuals trapped in 2004 and 2005, respectively. Large variations in species richness and diversity indexes were observed between fields within and between years. Multivariate analyses showed that carabid activity-density varied as a function of field location and sampling period, with individuals belonging to species overwintering as adults being more abundant early in the growing season. There was no relationship between carabid trap catches and A. glycinesdensity, suggesting that carabid beetles do not respond numerically to soybean aphid populations at the spatial scale studied.

AbstractThe study was conducted to document the spatial distribution of the soybean aphid, Aphis glycinesMatsumura (Hemiptera: Aphididae), in commercial fields of soybean, Glycine max (L.) Merr. The abundance of aphids was assessed weekly at 12 sites in 2005 and 2006 on more than 135 georeferenced plants per site. Variograms and principal coordinates of neighbour matrices (PCNM) were used to detect significant spatial structures. Variograms indicated a spatially random distribution of aphid populations in a majority (84%) of fields-weeks. For the variograms with a defined structure, the variance between pairs of observations generally increased rapidly with the distance between plants up to a distance where it stabilized, a pattern adequately fitted by spherical models. Structured spatial distributions were more prevalent in 2005 than in 2006, especially at the end of the season. In 2006, PCNM analysis was more sensitive in detecting spatial trends than were variograms. PCNM analysis revealed significant patterns across a broad range of scales, with dominant periods averaging 22.6 and 47.1 m for the short and long transects, respectively. Sampling plants along a 100 m long transect at about 7.5 m intervals in soybean fields would allow detection of the spatial structures identified in this study.

AbstractA study was conducted in 2004 and 2005 to test the hypotheses that the severity of damage caused by the soybean aphid, Aphis glycines(Hemiptera: Aphididae), is minimized by the activity of predators and declines with the maturity of soybeans, Glycine max(L.) Merr. (Fabaceae), at the time of infestation. In caged subplots where predators were excluded, aphids attained a high density following experimental infestation of soybeans, resulting in severe reductions of yield, particularly when plants were infested early in the season. A guild of generalist predators consisting predominantly of ladybird beetles colonized plants in uncaged subplots, resulting in a low rate of population growth following infestation of soybeans with aphids and a relatively weak impact on the soybean yield. The soybean yield declined as the density of aphids (number per plant), and the maturity of soybeans at the time of infestation, increased. Our results suggest that A. glycinesrepresents an occasional pest of soybean in Quebec, because of (i) temporal asynchrony between the late-season infestation by aphids and the most susceptible phenological stage of soybeans (vegetative or flowering) and (ii) biological control by natural enemies.

Abstract: Since its invasion of North America in 2000, the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae) has notably changed the arthropod community of the soybean agroecosystem. The objectives of this study were to characterize the foliar predatory fauna associated with A. glycines in commercial soybean fields in Québec, Canada, and to evaluate the suitability of A. glycines as prey for three coccinellid species: Harmonia axyridis Pallas, Propylea quatuordecimpunctata L. and Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Field surveys showed that several predators responded rapidly to expanding and increasing populations of the soybean aphid. Coccinellidae were the most important aphidophagous predators observed in 2002 (58.6%) and 2003 (44.8%), with mainly four native and naturalized species co-occurring with the soybean aphid throughout the growing season. Measurement of fitness parameters under laboratory conditions (survival, development time, longevity, fecundity) indicated that A. glycines is an excellent prey for the development and reproduction of all three of the coccinellid species studied. The intrinsic rate of natural increase (rm) was highest for H. axyridis (0.238 d−1), intermediate for P. quatuordecimpunctata (0.215 d−1) and lowest for C. maculata (0.134 d−1).

Corn rootworms, DiabroticaChevrolat spp. (Coleoptera: Chrysomelidae), are major pests of corn, Zea maysL. (Poaceae), in North America. Overwintering eggs hatch in the spring, and larvae feed on the root system, where they complete development. Emergent adults feed on vegetative and reproductive aerial structures of corn and oviposit in soil cracks or at the base of plants. Although feeding on silks by adult corn rootworms reduces the yield of corn, most of the damage results from root injury caused by larval feeding (Levine and Oloumi-Sadeghi 1991).

Abstract: The intrinsic rate of natural increase(rm) is useful to estimate the populationgrowth potential of insects and mites, whichmay help predict the outcome of pest-naturalenemy interactions. This study was conductedto determine how 12 constant temperatureregimes between 10–38 °C (± 0.5 °C) may differentially affect therm of the McDaniel spider mite, Tetranychus mcdanieli McGregor (Acarina: Tetranychidea), a common pest of raspberry, andits coccinellid predator, Stethoruspunctillum Weise (Coleoptera: Coccinellidae). Tetranychus mcdanieli survived tomaturity in the 14–36 °C range, comparedto the 14–32 °C range for S.punctillum. Survival above 24 °Cremained high for the spider mite, butdecreased markedly for the coccinellid. Tetranychus mcdanieli's range forreproduction was similar to its survival range,but S. punctillum failed to reproduce at14 °C and reproduced only poorlyat 16 °C. Offspring production peakedat 24 °C for both T. mcdanieli(average 152 eggs per female), and S.punctillum (280 eggs per female). At alltemperatures suitable for reproduction, femalelongevity of the coccinellid was greater thanthe spider mite, which was characterized byearlier/faster reproduction than thecoccinellid. As temperature increased, therm followed a typical asymmetricaldome-shape pattern, with maximum values of0.196 d–1 and 0.385 d–1at 30 °C and 34 °C, for S.punctillum and T. mcdanieli,respectively. For each species, therm-temperature relation was successfullymodelled using a curvilinear regressionequation previously shown to predictdevelopment rate. In both species, thedevelopment rate response to temperature has amajor influence on the temperature-rmrelationship. In the 16–32 °C rangesuitable for population growth of both species,the rm of T. mcdanieliwas 1.9 (30 °C) to 8 (16 °C) times greaterthan S. punctillum. These growthpotential ratios are consistently in favor ofthe prey, suggesting a limitation of thecoccinellid with respect to its capacity totrack T. mcdanieli populations. However,under short season conditions, the inferiorreproductive dynamics of S. punctillum'svs. spider mite prey should not have aprevailing influence in determining impact, andmay be compensated by high voracity incombination with a strong aggregativeresponse.

Paired choice experiments were used to evaluate host feeding and oviposition preferences of Cephalonomia stephanoderis(Hymenoptera: Bethylidae), a solitary ectoparasitoid of the coffee berry borer (CBB), Hypothenemus hampei(Coleoptera: Scolytidae). Immature and ovipositing females may feed on all developmental stages of the host, but prefer eggs and adults. Parasitoid females parasitize prepupae, pupae, and full-grown larvae of H. hampei,the latter stage being least preferred. Ovipositional decisions of C. stephanoderisfemales lead to the selection of the most profitable host stage for parasitoid development because parasitoids developing on larval hosts took more time to reach the adult stage and were smaller than those developing on prepupal and pupal hosts. The behavioral plasticity of C. stephandoderisin CBB host stage selection for both host feeding and oviposition may contribute to the survival and establishment of C. stephanoderisas a biological control agent of H. hampeiin coffee plantations.

The ability of the mycoparasite, Verticillium lecanii(Zimm.) Vegas, to trigger plant defense reactions was investigated using Ri T-DNA transformed cucumber roots subsequently infected with the root pathogen,Pythium ultimum. The antagonistic potential of V. lecaniiagainst P. ultimumwas determined in dual culture tests. Cytological investigations of V. lecanii-inoculated cucumber roots revealed that the fungus grew actively at the root surface and colonized a small number of epidermal and cortical cells, without inducing extensive host cell damage. Direct cell wall penetration was seldom observed and Verticilliumingress into the root tissues proceeded via an intercellular route. In V. lecanii-free roots, the pathogen multiplied extensively through much of the tissues while inV. lecanii-treated roots, pathogen growth was restricted to the epidermis and the outer cortex. At the root surface,V. lecaniiinteracted with P. ultimumin a way similar to that observed in vitro. However, a novel finding concerned the structural alteration of P. ultimumhyphae that penetrated the root tissues. This was clearly shown by the frequent occurrence of empty fungal cells in intercellular spaces colonized by V. lecanii. Pythiumingress in the root tissues resulted in the deposition of an electron-opaque material frequently encircling pathogen hyphae and also accumulating in the noninfected xylem vessels, suggesting that the host plant was signalled to defend itself through the stimulation of defense mechanisms. The present observations provide the first convincing evidence that V. lecaniimay colonize root cells and trigger plant defense reactions in addition to being an efficient mycoparasite.

We reviewed the literature on aphid parasitoids to determine the occurrence, nature and outcome of intraguild interactions. Intraguild interactions were described for larval, pupal and adult aphid parasitoids and by the type of natural enemy (fungus, predator, or parasitoid). They appear to be prevalent in most aphid parasitoid systems and, except for parasitoid‐parasitoid interactions, they are mostly asymmetric, with aphidophagous predators and pathogens killing parasitoids. The limited experimental evidence from field studies is insufficient to provide a comprehensive pattern of the consequences of intraguild interactions for aphid parasitoid populations in general and, more specifically, for the efficacy of biological control. However, because intraguild interactions are widespread in aphid‐natural enemy communities and mostly detrimental to aphid parasitoids, we conclude that intraguild interactions have a primary effect in driving fluctuations in aphid parasitoid populations. Drawing on case studies, we further argue that intraguild interactions can substantially alter the effectiveness of aphid parasitoids as biological‐control agents.

We describe behavioral sequences and daily activities of pre-ovipositing and ovipositing females of Cephalonomia stephanoderis(Hymenoptera: Bethylidae), an ectoparasitoid of the coffee berry borer, Hypothenemus hampei(Coleoptera: Scolytidae). Noticeable behavioral differences among preovipositing and ovipositing females include host examination, host stinging—probing, host feeding, and the oviposition per se. The female of C. stephanoderisfeeds primarily on host eggs, but pupae are also exploited, mainly by pre-ovipositing females. After the onset of the oviposition period, C. stephanoderisexamines the pupae repeatedly, stings them at frequent intervals, and spends more time feeding than during the pre-oviposition period. Host paralysis is linked both to host feeding and oviposition. It induces irreversible developmental arrest, which presumably allows preservation of the host until subsequent utilization, and contributes to successful offspring development, particularly by reducing host motility. Oviposition consists in a host selection process, a prolonged period of preparation of the potential host, and the egg-laying phase itself. Under our experimental conditions, pre-ovipositing and ovipositing females are active 17% and 36% of the day, respectively. Host handling time averages 6% and 23% in pre-ovipositing and ovipositing females, respectively. All coffee berry borer developmental stages are exploited by C. stephanoderisfemales, either for host feeding and/or oviposition activities. Such flexible behavior is advantageous given that host availability is limited inside the coffee berries.

The effect of the density of the coffee berry borer, Hypothenemus hampei(Coleoptera: Scolytidae) on reproductive and host‐feeding behaviours of the parasitoid Cephalonomia stephanoderis(Hymenoptera: Bethylidae) was evaluated under laboratory conditions. The number of hosts used for oviposition was density‐dependent at low host density. Beyond a density of six hosts/day, the oviposition rate reached a maximum of 1.2 eggs/day due to egg limitation. Cephalonomia stephanoderisfemales responded to increasing host availability with a linear increase in host feeding. Overall, parasitoids killed more coffee berry borers by feeding and paralysis than by parasitism. At low host density, the pre‐oviposition phase was extended, oogenesis was delayed, more males were produced, and host feeding occasionally occurred concurrently with oviposition. We suggest that the efficacy of C. stephanoderisas a biological control agent depends on seasonal variations in host density. Inoculative vs inundative releases in coffee plantations are discussed in relation to the abundance of the coffee berry borer during the fructification and interharvest periods.

Chronological events of the interaction between the hyphomycete Verticillium lecaniiand the potato aphid Macrosiphum euphorbiaewere investigated by light, scanning, and transmission electron microscopy. The parasitism of M. euphorbiaeby V. lecaniiappears to involve the following events: (i) adherence of conidia to the host cuticle through a thin mucilagenous matrix; (ii) germination of the conidia and production of mycelium that colonizes the surface of the cuticle; (iii) penetration of germ tubes into the aphid cuticle 24 h after application of the pathogen; (iv) extensive lateral development of hyphae accompanied by pronounced degradation of the cuticular layers by 72 h. Labeling with the WGA/ovomucoid–gold complex showed that penetration and colonization of the cuticle by the fungus resulted from localized enzymatic hydrolysis, likely through the synergistic action of chitinases and mechanical pressure; (v) production of blastospores and massive invasion of aphid internal tissues; (vi) assimilation of nutrients and accumulation of lipids by fungal cells; and (vii) production of conidiophores and release of the fungus from aphid cadavers. These observations bring further insights into the mechanisms by which V. lecaniiparasitizes M. euphorbiae.They also provide a basis for comparing the modes of action of V. lecaniiagainst hosts from fungal and animal origins.

AbstractPredation experiments were conducted to identify a predator with the capacity to control the tomato russet mite, Aculops lycopersici(Massee) (Eriophyidae), in greenhouse tomato crops. The efficiency of four predatory mites species was evaluated at the individual level in the laboratory: the tydeid Homeopronematus anconai(Baker) and the phytoseiids Phytoseiulus persimilisAthias-Henriot, Amblyseius cucumerisOudemans, and A. fallacisGarman. The first three species had already been suggested as potential control agents. Predation by P. persimiliswas essentially zero on tomato russet mite, whereas H. homeopronematusfailed to develop to the adult stage when fed solely with this prey. Amblyseius cucumerisdeveloped successfully on tomato russet mite but failed to reproduce. Only A. fallacisappears to possess several of the biological attributes required to control the tomato russet mite. This species attacks all stages of the pest and displays excellent survival (.92%), adequate rate of development (6.3 days at 22 °C), and good reproductive capacity in the presence of A. lycopersici.

AbstractAspects of the life history of the aphid hyperparasitoid Asaphes vulgarisWalker, when reared on Aphidius nigripesAshmead, were investigated under laboratory conditions. Longevity was significantly related to temperature and to the sex of adults. Female life span was about 4 months at 15 °C compared with 46 days at 25 °C; under the same conditions male longevity was 66 and 19 days, respectively. Females started to oviposit in aphid mummies upon eclosion and lifetime fecundity was high, reaching 1433 offspring. The sex ratio (proportion of males) was low early in reproductive life but rose sharply after several weeks. The implications of these results on the efficacy of A. nigripesin the potato agrosystem are discussed. It is suggested that high hyperparasitoid fecundity and longevity might play a role in reducing the impact of the primary parasitoid.

Mating in the aphid parasitoid,Aphidius nigripes, is mediated by a female sex pheromone that stimulates both upwind flight and courtship behavior by males. There is no evidence of any overt behavior associated with the release of the pheromone, but bioassay results, using female extracts, suggest that the pheromone is produced in the abdomen, although it may be actively released from the entire body surface. Age does not appear to have a major influence on either pheromone production by the female or on male responsiveness. However, field data suggest the presence of a strong diel periodicity in the emission of and/or receptivity to the pheromone. Laboratory bioassay results indicated diel changes in the male response but more refined techniques are needed to determine if such periodicity exists in pheromone production by females. Following mating, female pheromone production is significantly reduced. The potential use of the parasitoid sex pheromone in integrated management of aphids is discussed.

Host specificity and host selection by insect parasitoids are hypothesized to be correlated with suitability of the hosts for parasitoid development. The present study investigates the correlation between host suitability and earlier studied host‐finding behaviour of two closely related braconid larval parasitoid species, the generalist Cotesia glomerata(L.) and the specialist C. rubecula(Marshall) (Hymenoptera: Braconidae). We compared the capability of both parasitoid species to parasitize and develop in three Pierishost species, i.e. P. brassicae(L.), P. rapae(L.) and P. napi(L.) (Lepidoptera: Pieridae). In laboratory experiments, we measured the effect of host species on fitness parameters such as survival, development, sex ratio and size of parasitoid progeny. The results show that C. glomeratais capable of developing in the three host species, with significant differences in parasitoid survival, clutch size and adult weight among Pierisspecies. The host range for development was more restricted for C. rubecula. Although C. rubeculais physiologically able to develop in P. brassicaelarvae, parasitoid fitness is negatively affected by this host species, compared to its most regular host, P. rapae. A comparison of the present data on host suitability with earlier studies on host‐searching behaviour suggests that the host‐foraging behaviour of both parasitoid species not only leads to selection of the most suitable host species for parasitoid development, but also plays a significant role in shaping parasitoid host range.

Aphidius nigripesAshmead, an endoparasitoid of the potato aphid, Macrosiphum euphorbiae(Thomas), not only has the ability to modify host behavior, but does so differently depending on its physiological state. A previous study indicated that just prior to death, parasitized aphids that contain diapausing parasitoid larvae leave the host plant to mummify in concealed sites, while those containing nondiapausing parasitoids generally remain on the plant. This study explored the proximal factors involved in the selection of an overwintering microhabitat by a host containing a diapausing A. nigripeslarva. Parasitized aphids showed negative phototaxis, thigmokinesis, and chose a dark rather than a light-colored substrate when seeking a site to mummify. However, their behavior was not influenced by either gravity or the presence of another mummy. The combined effects of these behavioral patterns would result in dormant parasitoids overwintering in sheltered sites, thereby reducing the negative effects of adverse climatic conditions and the actions of natural enemies. The utilization of these proximal cues may also enhance parasitoid, survival by reducing aphid wandering time prior to mummification.

We explored associations between the common protozoan parasite Toxoplasma gondiiand brain cancers in human populations. We predicted that T. gondiicould increase the risk of brain cancer because it is a long-lived parasite that encysts in the brain, where it provokes inflammation and inhibits apoptosis. We used a medical geography approach based on the national incidence of brain cancers and seroprevalence of T. gondii. We corrected reports of incidence for national gross domestic product because wealth probably increases the ability to detect cancer. We also included gender, cell phone use and latitude as variables in our initial models. Prevalence of T. gondiiexplained 19 per cent of the residual variance in brain cancer incidence after controlling for the positive effects of gross domestic product and latitude among nations. Infection with T. gondiiwas associated with a 1.8-fold increase in the risk of brain cancers across the range of T. gondiiprevalence in our dataset (4–67%). These results, though correlational, suggest that T. gondiishould be investigated further as a possible oncogenic pathogen of humans.

The cabbage seedpod weevil, Ceutorhynchus obstrictus(Marsham) [= C. assimilis(Paykull)] (Colonnelli 1993), is a univoltine species native to Europe that feeds on canola and other oilseed cruciferous plants. The adult overwinters in debris and soil outside fields and colonizes canola at the blooming stage (Dosdall et al.2001). Eggs are laid singly into the immature pods and each larva consumes five to seven seeds before cutting a hole in the pod to wriggle out and pupate in the soil (Dmoch 1965). Yield losses are difficult to assess because the plant compensates for bud and pod injuries caused by insects or pathogens (Lamb 1989). Nevertheless, pod feeding by larvae causes much damage, as canola yields can be reduced from 15 to 35% (Homan and McCaffrey 1993). Feeding by adults can also be significant, as it can reduce oil content, seed weight, and seed germination (Buntin et al.1995).

The cranberry girdler, Chrysoteuchia topiaria(Zeller) (Lepidoptera: Pyralidae), is the most important sod webworm species attacking turfgrasses in Quebec, Canada (Simard 2001). Unlike other webworms, the cranberry girdler is rarely observed on grass blades but feeds on the crowns and roots in the thatch. Biopesticides based on a nematode–bacterium complex appear to hold promise as a means of controlling turfgrass insect pests, particularly those that colonize the thatch and the first few centimetres of soil (Potter 1998), such as the cranberry girdler (Georgis and Hague 1991). Our objective was to assess the susceptibility of the cranberry girdler to entomopathogenic nematodes. In the laboratory, we determined the LC50values for four nematode species and evaluated the effect of contact time on host mortality.

This study investigated the effects of partial plant resistance on the lettuce aphid Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae), a major pest of cultivated lettuce (Lactuca sativa L.), and one of its parasitoids, Aphidius ervi Haliday (Hymenoptera: Braconidae). Aphids were reared on susceptible (L. sativa variety Estival; S) or partially resistant (Lactuca serriola L. PI 491093; PR) lettuce, and next parasitized by A. ervi females. Fitness proxies were measured for both aphids and parasitoids. Developmental time to adult stage took longer for alate and apterous aphids (an average of 3.5 and 1.5 additional days, respectively) on PR than on S lettuce, and fecundity of alate aphids reared on PR lettuce was reduced by 37.8% relative to those reared on S lettuce. Size (tibia length) and weight of aphids reared on PR lettuce were lower than for aphids reared on S lettuce from the third and second instar onward, respectively. Parasitism of aphids reared on PR plants resulted in lower parasitoid offspring emergence (-49.9%), lower adult female (-30.3%) and male (-27.5%) weight, smaller adult female (-17.5%) and male (-11.9%) size, and lower female fecundity (37.8% fewer eggs) than when parasitoids developed from aphids reared on S plants. Our results demonstrate that partial aphid resistance in lettuce negatively affects both the second and third trophic levels. Host plant resistance in cultivated lettuce may therefore create an ecological sink for aphid parasitoids.

In recent years, the soybean aphid, Aphis glycines Matsumura, has become the most important exotic pest of soybean, Glycine max (L.) Merrill, in North America. Given the significant yield losses that are reported, considerable effort has been expended to characterize the natural enemy community associated with this pest. Several indigenous and naturalized predators have been identified as potential biological control agents, and these include carabid beetles, an abundant and important family of aphid predators. The objectives of this study were to assess the incidence of field predation by Pterostichus melanarius (Illiger), the most common carabid species in Québec soybeans, using molecular gut-content analysis, and to quantify its impact on A. glycines populations through laboratory and field cage experiments. Throughout the growing season between 16.8% (during low aphid density) and 33.7% (at times of high aphid density) of P. melanarius tested positive for aphid DNA. Furthermore, although laboratory feeding trials confirmed that P. melanarius prey on A. glycines, short-term field cage experiments failed to demonstrate a significant reduction of A. glycines populations by carabid beetles. These results suggest a relatively weak interaction between P. melanarius and A. glycines when pest densities are high, but the high predation rate when aphid densities are particularly low suggests these natural enemies may function as important early-season predators.

We describe seasonal patterns of parasitism by Telenomus coloradensis Crawford, Telenomus droozi Muesebeck, Telenomus flavotibiae Pelletier (Hymenoptera: Scelionidae), and Trichogramma spp. (Hymenoptera: Trichogrammatidae), egg parasitoids of the hemlock looper, Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae), after a 3-yr survey of defoliated stands in the lower St. Lawrence region (Quebec, Canada). Results from sentinel trap sampling indicate that T. coloradensis and T. droozi are the most common species, whereas parasitism by T. flavotibiae and Trichogramma spp. is rare. Telenomus coloradensis and T. droozi show similar seasonal periods of parasitism, both species being active in early spring (late April) at temperatures as low as 4°C. Using thermal threshold (T0 ) and thermal constant (K) for immature development of T. coloradensis males and females from egg to adult emergence, we estimated that the spring progeny emerges in the middle of the summer while hemlock looper eggs are absent from the forest environment. Parasitoid females would then mate and remain in the environment to 1) exploit alternate host species, 2) enter into quiescence and later parasitize eggs laid by hemlock looper females in the fall, 3) enter into a reproductive diapause and parasitize hemlock looper eggs only the next spring, or all of these. Although previous studies have shown that T. coloradensis can overwinter in its immature form within the host egg, our field and laboratory results indicate that in the lower St. Lawrence region, this species principally enters diapause as fertilized females, with a mean supercooling point of -30.6°C in the fall.

The weevil Listronotus maculicollis Dietz (Coleoptera: Curculionidae) is a major pest of annual bluegrass, Poa annua L., on golf courses in northeastern North America. To determine the distribution, abundance, and seasonal ecology of L. maculicollis on golf courses in Québec, Canada, we sampled 19 golf courses (GC1–GC19) from different geographic and climatic conditions during 2001, 2002, and 2003. L. maculicollis was found on all golf courses except GC19, which was located in northeastern Québec. In most sites, L. maculicollis completed two generations per year. A linear regression model comparing L. maculicollis larval densities as a function of spatial coordinates revealed that L. maculicollis were more abundant in western Québec than in eastern Québec. Pearson correlations on the probability of both L. maculicollis larval and pupal presence with soil parameters indicated significant positive correlations for fine sand (larvae) and soil pH (pupae) and negative correlations for gravel.

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.