Location: Invasive Species and Pollinator Health
Project Number: 2030-22000-033-032-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Aug 1, 2024
End Date: Jul 31, 2026
Objective:
The objectives of this project are to: 1) Improve mass rearing of parasitoids; 2) Release the parasitoid Ganaspis brasiliensis at an areawide implementation site; 3) Monitor establishment and spread of G. brasiliensis at the implementation site; 4) Compare spotted wing drosophila (SWD) levels and parasitism rates between implementation and control sites.
Approach:
Parasitoids will be released at an implementation site in Watsonville, Santa Cruz Co., at Driscoll’s Berries. The implementation site will be paired with a control site of similar size ~13 km away in the Watsonville area. Sites will consist of large acreages of cane berries (blackberry and raspberry) and non-crop habitats containing wild blackberry. Each site will be ~250 acres and comprising 10-25% non-crop vegetation habitat. To prepare for mass releases, the imported parasitoid G. brasiliensis will be reared in at our U.C. Berekeley collaborator's laboratory. Parasitoid releases will start in late spring/early summer as fruits are infested and spotted wing drosophila (SWD) larvae/pupae are present. At least 2,000 G. brasiliensis per year will be released at a release point at the implementation site from July to October. Sites will be monitored from May to October when SWD is most active. Sites will have 1 sample point per 10 acres, 50 samples for two 250 acre fields. Each sample point will include a SWD monitoring trap containing apple cider vinegar and 500 g fruit collection. Fruit will be incubated in the lab in vented containers for two weeks to count adult SWD emergence. To assist growers with decision-making, weekly monitoring will occur before fruit ripening and when growers are actively managing SWD. Biweekly monitoring may occur at other less critical periods. To assess efficacy, we will compare adult fly counts and larval infestation between implementation and control sites with generalized linear mixed models with treatment as the fixed effect, site pair as a random block effect with an appropriate distribution. Parasitism will also be checked by placement of sentinel SWD larvae/pupae and berry collections in non-crop and field areas to confirm continued activity of the parasitoids.
