Exploration and Evaluation of the Native Parasitoids of Invasive Spotted-wing Drosophila, Drosophila suzukii for Biological Control

View the project final report

Commodities

• Fruits: berries (blueberries)

Practices

• Pest Management: biological control, integrated pest management

Drosophila suzukii (Matsumura) (Diptera Drosophilidae) commonly known as spotted-wing drosophila (SWD) is an invasive insect pest threatening many small fruit industries in the Americas and Europe for more than a decade. While many control approaches are being utilized in the invaded regions to manage this pest, biological control using parasitoids is one of the promising strategies for the sustainable management of SWD. We conducted a two-season-long field exploration for native parasitoids of SWD during 2021 and 2022 around major blueberry-producing locations in Georgia, United States. Fruit-baited sentinel traps infested with SWD eggs were placed around eight commercial blueberry orchards in Southeast Georgia. A total of 371 Drosophila-related parasitoids were collected and classified into three families: Figitidae, Pteromalidae, and Diapriidae. Among them, Leptopilina boulardi (Hymenoptera: Figitidae) and Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae) were the most abundant species in the collection.  Previously, only P. vindemiae was known to parasitize successfully on SWD. In subsequent laboratory testing, L. boulardi collected from Georgia also parasitized less than 7% of the SWD but failed to eclose as adults from the infested larvae. The number of parasitoids captured was higher during the peak blueberry ripening to harvest season compared to the flowering, fruiting, or after the fruits were harvested. Parasitoids were most abundant in the wild locations compared to cropped fields, but no difference was observed when organic fields and conventional planting systems were compared. This is the first account of any Drosophila-related native parasitoid survey conducted in Georgia. A follow-up project based on these outcomes was built for the classical release of an exotic parasitoid Ganaspis brasilensis (Hymenoptera: Figitidae) around the surveyed locations. A total of 14,164 G. brasilensis (8493 females and 5671 males) were released around these locations and are being closely monitored.

This project will focus on exploring, collecting, identifying, and testing the efficiency of key parasitoids of the SWD in the newly invaded habitats, particularly in fruit-growing regions of the southeastern U.S. The specific objective of this project will be:

(1) To explore and collect the larval and pupal parasitoids of the SWD in the blueberry orchards, other fruit crop farms, and alternative wild habitats. The project focused on exploration and collection of parasitoids on many blueberry orchards, other small fruit orchards, and the nearby wild habitats of those orchards located mainly in Georgia, USA. 

 (2) To study the abundance, distribution, and habitat selection of the native parasitoids of SWD in Georgia. This objective targeted the understanding of the relationship of the parasitoids with their habitat composition, diversity, and their association at a temporal and spatial scale.

(3) Evaluate the biology, life history, and host selection of native parasitoids concerning their SWD population in these habitats. The collected parasitoids were reared in the laboratory and were tested for their efficiency to parasitize the D. Suzukii. If a new species parasitoid was discovered that was not previously reported in either Georgia or even in the U.S., they were further tested and evaluated for their association to SWD parasitism.