Distribution of three figitid parasitoids of Drosophilidae in Washington State: a tale of 2 ecozones.

Abstract

The geographic distribution and relative abundance of 2 adventive Asian parasitoids (Ganaspis kimorum Buffington and Leptopilina japonica Novković & Kimura) (Hymenoptera: Figitidae) of spotted-wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae) in Washington state were surveyed from 2020 to 2024 using bait or lure traps. G. kimorum and L. japonica were first detected in 2020 to 2021 in western Washington. However, their distribution in eastern Washington, which produces the majority Washington's vulnerable specialty crops, was of interest for establishing a baseline for future biological control efforts. A clear picture emerged regarding the current distribution of the 2 Asian species, and a cosmopolitan figitid, Leptopilina heterotoma (Thompson), which attacks other Drosophila spp. Adventive populations of G. kimorum were only found west of the Cascade Mountains; the few specimens recovered in eastern Washington were found near release sites. Conversely, L. heterotoma was rarely detected using jar traps in western Washington, but was the most abundant of the figitid species found in eastern Washington. L. japonica was common and abundant in both regions, but more so in western Washington. The unaided establishment of L. japonica in eastern Washington may presage its future impact as a biological control agent in this region.