The Use of UAS to Release the Egg Parasitoid Trichogramma spp. (Hymenoptera: Trichogrammatidae) Against an Agricultural and a Forest Pest in Canada.

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.

A molecular revision of the taxonomic status of mermithid parasites of black flies from Quebec (Canada).

The four currently recognized mermithid (Nematoda) species parasitizing black flies (Diptera: Simuliidae) from Northeast America were distinguished using discriminatory PCR primers aimed at COI and 18S rDNA. Isomermis wisconsinensis, Gastromermis viridis and Mesomermis camdenensis were easily differentiated using either genomic target, even for juvenile mermithids damaged beyond morphological recognition. However, specimens from Mesomermis flumenalis being identical in external morphology and producing a unique-sized PCR product were classified by sequence data into four clearly distinguished molecular variants. This quartet was made of two winter and two summer 'physiological variants', including one which also belonged to, but diverged early from the rest of the Mesomermis genus. Combining the multiplex PCR and sequencing approaches allowed for the characterization of a multiple parasitism which simultaneously implicated I. wisconsinensis and two M. flumenalis variants. With another instance where parasites were identified by morphology only, this is the first report of black fly parasitism by multiple mermithid species. A phylogenetic tree built by combining our sequences to previous GenBank entries likely indicates a monophyletic origin for the mermithid family, but also suggests that differentiation between parasite genera sometimes occurred before the evolutionary emergence of the actual host group.

Mermithids (Nematoda: Mermithidae) parasitizing different blackfly (Diptera: Simuliidae) populations in Quebec: environmental parameters related to their presence or absence in the studied brooks.

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.