D3472: Parasitism of spotted-wing drosophila larvae Drosophila suzukii by Ganaspis brasiliensis in different shaped raspberry or blueberry-based diet

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a global invasive pest attacking soft-skinned fruit. The larval parasitoid wasp, Ganaspis brasiliensis (Ihering), is a specialist larval parasitoid of D. suzukii that was recently approved in Europe and the United States for classical biological control releases against D. suzukii. We compared the performance and development of D. suzukii and G. brasiliensis on raspberry and blueberry fresh fruit and on different artificial diet shapes and volumes. Drosophila suzukii had 1-2 day shorter larval, pupal, and adult development times in raspberry than blueberry fruit, whereas Ganaspis development to adult was similar in both fruit and averaged 25 days. Parasitism rates by G. brasiliensis were higher in blueberry (40%) than raspberry (20%), but development times of D. suzukii larvae on blueberry artificial diet was longer compared to raspberry diet. We found that D. suzukii preferred to lay eggs in full sphere diets than semi-sphere or flat Petri dishes. No parasitism was found on 4 or 8 ml diets in a Petri dish or in semi-sphere shapes, whereas we found approximately 10% parasitism rates on full spheres made of a raspberry diet. In a follow-up comparison of parasitism on full sphere raspberry and blueberry diets, we found significantly higher parasitism in raspberry than blueberry diet. The potential for improvement of artificial rearing systems for G. brasiliensis that allow for most cost-effective rearing will be discussed for supporting biological control programs.