Location: Beneficial Insects Introduction Research Unit
Project Number: 8010-22000-031-098-A
Project Type: Cooperative Agreement
Start Date: Jul 1, 2024
End Date: Aug 31, 2025
Objective:
To establish the introduced parasitoid Ganaspis brasiliensis, monitor its impact on Spotted-wing drosophila and understand some key ecological factors that might affect the establishment and efficiency of this parasitoid in the mid-Atlantic region. The agreement supports objective 1 of the outlined work plan funded by APHIS.
Approach:
Objective 1 – Field release of G. brasiliensis in mid-Atlantic states:
ARS will conduct release of G. brasiliensis in Maryland, and monitor its establishment and impact (parasitism) while also document resident parasitoid species associated with SWD and related frugivorous Drosophila through pre- and post-release fruit samplings. We will select at least 3 sites that preferably represent typical non-crop habitats for SWD (e.g., forest edge or wild vegetation bordering berry/cherry farms) in this region. These non-crop habitats likely serve as reservoirs of SWD populations. Establishment of G. brasiliensis may help permanently reduce fly populations over large areas, making other management strategies more economically and efficiently. All release sites will be selected after some preliminary fruit samplings to ensure the occurrence of SWD in the area before the first release and have ideally abundant host fruits for SWD throughout the fruit seasons (July to October). Pre-release fruit samplings will be conducted immediately prior to each release to document the presence /absence of any parasitoids associated with SWD and/or related Drosophila. Post-release fruit samplings will be followed one week after each release and then once per month throughout the fruit seasons to monitor the establishment, dispersal, and levels of parasitism by G. brasiliensis. The parasitoid will be mass reared at Beneficial Insects Introduction Unit (BIIRU) and shipped to cooperators at each state for release. Wasps will be held in drosophila vials and, depending on the landscape characteristics of the release site and host plant distribution, vials will be distributed evenly among different patches within 100 m. Fruits will be sampled in the area within a 100 m radius of the release site (additional sampling may be taken at farther distances to determine the dispersal of the parasitoid for the final post-release sampling). Emphasis should be placed on sampling different host fruits in the area. Collected fruit will be held in plastic containers at suitable conditions to rear, collect and sort fly puparia (according to sub-sample date, site, plant /patch, host species, fruit types etc.). Following emergence of flies and wasps from puparia, the number of flies and wasps will be counted, and all collected flies and parasitoids will be preserved in 95% alcohol for later identifications. As described above all puparia will be later examined for the calculation of percentage parasitism.
