Susceptibility of apple cultivars to spotted wing fruit fly, Drosophila suzukii (Diptera: Drosophilidae)

Abstract

The species Drosophila suzukii, commonly known as the spotted-wing drosophila, is considered a primary pest of small fruits. However, there are also reports of its occurrence in damaged apples. Given the importance of apple cultivation in the state of Santa Catarina, this study aimed to evaluate the susceptibility of fruits from three apple cultivars (Elenise, Isadora, and Lorenzo) to D. suzukii damage. In no-choice bioassays, each experimental unit received three females and one male of D. suzukii, along with one fruit from each cultivar, respectively. In choice bioassays, each unit received eight females and two males of D. suzukii, in addition to three fruits, one from each cultivar. In both bioassays, D. suzukii adults were removed from the cages after 24 hours of exposure. After this period, the number of eggs laid on the fruits was counted. Fruits with oviposition were individually stored in plastic containers, and the number of emerged insects was recorded up to 14 days after egg laying. Both bioassays followed a randomized complete block design with ten replicates each. In the no-choice experiment, fruits from all three cultivars received oviposition; however, only the eggs laid on the Lorenzo cultivar developed into adults. In the choice experiment, oviposition occurred only on fruits of the Elenise cultivar, but no adult emergence was observed. Apple fruits proved to be suboptimal hosts for D. suzukii, highlighting the need for further studies on the species' preference for damaged fruits.