Jacques Brodeur’s research while affiliated with University of Quebec in Montreal and other places

Native to Japan, Popillia japonica is invasive in North America. Adult and larval P. japonica have different diets, but both cause aesthetic damage and yield losses in ornamentals, turfgrasses, and agricultural crops. The lack of co-evolved natural enemies in the invaded range has contributed to challenges associated with managing P. japonica in North America. Some generalist predators have been identified, but do not appear to impact the population. Entomopathogenic nematodes, including Heterorhabditis bacteriophora, have shown promise as biological control agents. A Dipteran parasitoid of adult P. japonica, Istocheta aldrichi was released and established in the eastern United States and is now present in eastern Canada. Its biology and potential as a biological control agent of P. japonica in Canada is reviewed.

Drosophila suzukii, spotted-wing drosophila, is an invasive pest in Canada that can lay its eggs into fresh fruits, unlike many of its close relatives. Larval feeding inside fruit causes the fruit to spoil prematurely. Some parasitoids have been found attacking D. suzukii larvae and pupae in regions that D. suzukii has invaded, including Asobara cf. rufescens in Canada. A parasitoid from Asia, Ganaspis kimorum, has the narrowest host range of the parasitoids identified in the native range of D. suzukii and has been approved for release in some countries. In 2019, an adventive population of G. kimorum and of another parasitoid, Leptopilina japonica, was detected in British Columbia, where research is now being conducted to determine if these parasitoids attack native species of Drosophila. The chapter also reviews the predators, pathogens, and use of sterile insect technique for biological control of D. suzukii.

The brown marmorated stink bug, Halyomorpha halys, is now established in Ontario, British Columbia, and Quebec in Canada. Nymphs and adults of H. halys damage plants by sucking on buds, fruits, and stems; feeding injury can result in scarred, misshapen and deformed plant structures. Halyomorpha halys are a nuisance in homes and other buildings. Several parasitoids of H. halys have been identified, with Trissolcus japonicus being one of the most promising candidates for biological control. A petition to release T. japonicus in Canada was not approved; however, adventive populations of T. japonicus are now established in North America. Studies to determine the impact of native natural enemies on H. halys and additional research on T. japonicus in Canada are discussed.

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.

Cultivated peatland (Histosol) in Southern Québec (Canada) is a rapidly declining non‐renewable resource used to grow most Canadian lettuce ( Lactuca sativa L., Asteraceae). Rolled‐rye ( Secale cereale L., Poaceae) cover crop is one of the conservation practices proposed to reach a more sustainable lettuce production, but the overall impact on the agroecosystem remains poorly studied in Histosols. We assessed multiple effects of rolled‐rye cover crop on the trophic chain associated with the lettuce aphid, Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae), a major pest of lettuce. During one growing season and through two consecutive lettuce crops, we monitored in situ the impacts of rolled‐rye cover crop on insect fauna and lettuce quality. We used visual scouting and yellow pan traps to assess plant colonization by N. ribisnigri , its natural enemies, and alternative prey. Exclusion cage experiments were also conducted to measure aphid fitness and population growth. Under greenhouse conditions, following cover crop removal, we examined potential lingering effects of rye within the soil on lettuce plants and N. ribisnigri . In situ experiments showed that rolled‐rye cover crop has the potential to inhibit N. ribisnigri field colonization and recruit natural enemies and alternative prey in the first lettuce crop. Rye also reduced aphid fitness as well as lettuce foliar amino acid concentration and weight. For the second lettuce crop, an almost 50% reduction in N. ribisnigri abundance was observed with the use of rolled‐rye cover crop. In greenhouse experiments, no persistent effect of rye was observed on the quality of lettuce grown with soil collected under a cover crop, nor on the fitness of aphids inoculated on these lettuces. This study highlights the diversity of trophic effects rolled‐rye cover crop may have on lettuce production in Histosols and the potential of rolled‐rye cover crop as a cultural practice to reduce aphid populations. Mechanisms at play while underlining agronomic challenges regarding proper rye termination must be further explored to maintain high‐performing lettuce yields.

Egg-laying decisions by female insects should balance aspects related to immature survival and foraging profitability of emerging larvae. Using field-captured individuals, we characterized the egg distribution of Istocheta aldrichi (Diptera: Tachinidae) on the body of its adult host, the Japanese beetle Popillia japonica (Coleoptera: Scarabaeidae). We determined whether the pattern varies as a function of host sex and the number of eggs laid on a given host. Out of the 5667 eggs observed, 95.9% were located on the host pronotum. Furthermore, eggs on the pronotum were mostly positioned in the center of this sclerite and oriented perpendicular to the host body axis. The proportion of eggs placed on other parts of the host body increased with the number of eggs per host (superparasitism). Successful development of I. aldrichi into pupae was maximum for eggs laid on the host pronotum than for eggs laid on other parts of the host. Oviposition decisions in I. aldrichi are likely shaped by trade-offs between vulnerability to grooming by the host and foraging profitability of neonate larvae (i.e., their capacity to penetrate the host cuticle), but also by the mating and defensive behaviors of the Japanese beetle.

We 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. aldrichi was detected only in 2009. It is assumed that I. aldrichi spread 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. aldrichi is 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. aldrichi is now established in most areas of the province of Québec where the Japanese beetle is present.