Evaluation of rearing strategies for spotted-wing drosophila, Drosophila suzukii, in three media

Spotted-wing drosophila (SWD), Drosophila suzukii (Matsumura), is an invasive economically destructive pest of small fruit crops. Its success lies in the serrated ovipositor of the adult female fly, a unique trait allowing them to lay eggs directly into ripening fruit. In previous experiments testing the efficacy of insect growth regulators (IGRs) on adult SWD, there was difficulty quantifying oviposition, as the eggs and larvae are the same color as the current rearing medium. Laboratory bioassay design is crucial to testing the efficacy of chemical controls. This project evaluates three rearing media ( Formula 4-24® by Carolina Biological Supply, corn meal agar, and white grape agar) in 60x15mm petri dishes for ease of immature life stage evaluation, ensuring replicate uniformity, and improving fly health. Treatments A and B tested Formula 4-24®, treatments C and D used the corn meal agar, and treatments E and F tested the white grape agar. Treatments A, C and E had a 1:0 female to male ratio of adult flies, while B, D and F had a 3:2 female to male ratio. The greatest visibility overall was with white grape agar, making it the ideal medium for observing eggs and early larvae. However, as the least nutritive substance, larvae were observed exiting the petri dish and there were low levels of pupae present. Formula 4-24® and the corn meal agar diets were most successful for pupal development, the prior appeared to encourage higher oviposition based on larval counts.