Effects of spinosad-based fruit fly bait GF-120 on tephritid fruit fly and aphid parasitoids

Abstract

Abstract The spinosad-based fruit fly bait GF-120 has recently been developed as a primary tool for the area-wide control and eradication of tephritid fruit flies. In this study, we assessed the direct contact toxicity of GF-120 to three major parasitoids of tephritids in Hawaii: Fopius arisanus (Sonan), Diachasmimorpha tryoni (Cameron), and Pysttalia fletcheri (Silvestri) (Hymenoptera: Braconidae), as well as one aphid parasitoid, Aphidius transcaspicus Telenga (Hymenoptera: Aphidiidae). All four parasitoid species were susceptible to GF-120. Males and females were equally susceptible to GF-120 for all species. The 24-h LC 50 values for the opiine braconid species were in a narrow range (8.3–17.5 ppm). The aphidiid appeared to be more susceptible than the opiines, probably due to the stickiness of GF-120. We confirmed that adult F. arisanus (as a model species) do not feed directly on GF-120 either in the presence or the absence of honey and water resources. F. arisanus tasted, discriminated, and gave up GF-120 droplets after a brief ( F. arisanus were allowed to freely forage on host coffee branches sprayed with droplets at the recommended field rate for use of GF-120 (80 ppm), treatment mortality was significantly higher than control mortality (sprayed with water), and also increased with exposure time. Although GF-120 appears to be the most judicious of reduced-risk fruit fly baits currently available, our results suggest that area-wide application of GF-120 needs to be carefully monitored in situations where release or conservation of parasitoids is a prime concern.