Date of Award

Spring 5-9-2025

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Entomology

First Committee Advisor

Philip Fanning

Second Committee Member

Andrei Alyokhin

Third Committee Member

Allison Gardner

Abstract

The invasive spotted-wing drosophila (Drosophila suzukii) is a significant global pest of soft-skinned fruit, causing substantial economic losses due to its ability to oviposit in ripening fruit. Unlike other Drosophila species, D. suzukii females possess a serrated ovipositor, allowing them to lay eggs in intact fruit, leading to rapid infestations and increased management challenges. Originally native to Asia, D. suzukii was first detected in North America in 2008 in California and rapidly spread across the United States and Canada, becoming a serious agricultural threat. Traditional control methods rely heavily on chemical insecticides, which have contributed to resistance development and raised environmental concerns. As a result, sustainable management strategies, including biological control, have gained increasing attention. One of the most promising biocontrol agents for D. suzukii is Ganaspis kimorum, a larval parasitoid native to Asia with high host specificity. Based on the quarantine studies in Switzerland and California, including the host specificity studies of the G1 group, a petition submitted to USDA APHIS was approved for the release of the G. kimorum in the US. Overwintering is a critical phase in the life cycle of G. kimorum, as its ability to survive cold temperatures determines its long-term establishment and effectiveness as a biological control agent against D. suzukii. Successful establishment of G. kimorum in new environments depends on its overwintering survival and effective augmentation in agricultural landscapes. This study investigates the overwintering potential of G. kimorum in Maine through field and laboratory experiments assessing the impact of temperature, microhabitat conditions, and exposure duration. Field trials with soil-buried diapausing revealed significant declines, however low and persistent survival was observed out to 120 days in the field. To enhance G. kimorum populations, we evaluated the efficacy of augmentorium cages—tent-like structures designed to sequester D. suzukii-infested fruit while allowing parasitoid escape. Mesh trials determined the optimal mesh size to maximize G. kimorum emergence while preventing D. suzukii escape. Augmentorium field trials demonstrated significant temporal variation in parasitism rates, with peak parasitism occurring early in the season. Additionally, fruit collection outside the cage from untreated blueberry fields confirmed the presence of G. kimorum, suggesting that augmentorium cages successfully released the parasitoid and contributed to increasing its population in the field. Temperature differences between outside and the augmentorium cages also suggested microclimatic effects on parasitoid survival and efficacy. By integrating overwintering ecology with augmentorium-based biocontrol, this study provides critical insights into the long-term sustainability of G. kimorum as a biological control agent. These findings inform integrated pest management (IPM) strategies aimed at reducing D. suzukii populations while supporting beneficial parasitoid communities in temperate agroecosystems.

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