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Mass rearing of numerous biological control agents depends on large amounts of factitious hosts like Ephestia kuehniella eggs. Moreover, production of some parasitoids, such as Trichogramma, requires hosts of high quality. The objective of this study was to determine the optimal conservation method that allows E. kuehniella eggs to remain suitable for parasitism and development of Trichogramma ostriniae for the longest period of time. Fifteen sterilization-conservation treatments were compared: nine consisting of submersion of the eggs in liquid nitrogen as a conservation mode, two consisting of sterilization of the eggs with UV and four consisting of sterilization with freezing at À15°C. Liquid nitrogen submersion of E. kuehniella eggs did not allow the production of T. ostriniae. The sterilization by exposition to UV light followed by conservation using vacuum packing and refrigeration at 4°C provided the longest conservation of E. kuehniella eggs for T. ostriniae rearing. It was the only treatment (75.4 AE 4.62%) for which the parasitism rate remained over 70% after 2 weeks.

The egg parasitoid Trichogramma spp. (Hymenoptera: Trichogrammatidae) is a widely used biocontrol agent against lepidopteran pests. Historically, Trichogramma were deployed either by plane or by using cardboard cards on which parasitized eggs are glued and manually installed at sites. Plane deployment is costly and card installation is time consuming, but the use of Trichogramma has been shown to be efficient against several pests. In 2016 and 2017, a research project investigated the potential use of unmanned aerial system for distributing Trichogramma as biocontrol agents against two major pests: an agricultural pest of maize, the European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), and a forest pest, the eastern spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae). Exposure duration of parasitized eggs to field conditions (temperature, predation, etc.) in maize fields influenced the Trichogramma’s emergence rate, suggesting that timing of parasitoid releases with their emergence is essential. Although parasitism of naturally occurring eggs in maize fields could not be compared due to the low density of the European corn borer, parasitism of sentinel eggs by Trichogramma was more prominent in plots with unmanned aircraft systems (UAS)-releases compared to control plots. For spruce budworm, treatment with Trichogramma increased egg parasitism and there was no difference between the deployment by UAS and by Trichocards. We discuss these results in the context of pest biology and management. We also discuss the advantages and shortcomings of both methods and offer insights into where future work might go to further leverage the use of UAS in managing these important pests.

Specimens of Isomermis wisconsinensis, Gastromermis viridis, Mesomermis flumenalis, and Mesomermis camdenensis have been found in 14 out of 28 studied sites. Their hosts were the following blackfly species: Cnephia dacotensis, Cnephia mutata, Prosimulium sp., Simulium decorum, Simulium tuberosum, Simulium venustum/verecundum complex, and Simulium vittatum. Superparasitism was observed in several simuliid larvae and, occasionally, with 2 different mermithid species. The prevalence of different mermithid species varies according to seasons: Mesomermis genus is more abundant during winter, whereas Isomermis and Gastromermis are found in higher number during summer. The study of environmental parameters related to mermithid presence or absence shows that only stream depth makes a difference.