Bisexual releases are as effective as male-only releases to control Drosophila suzukii with the Sterile Insect Technique

BACKGROUND: The Sterile Insect Technique (SIT) suppresses insect reproduction by repeatedly releasing sterile insects and allowing them to mate with insects of the same species in the wild. While the classical SIT relies on sterile males mating with wild females, there is a debate regarding the risks and benefits of releasing sterile females along with the sterile males (i.e. bisexual releases). In a replicated cage experiment, we compared the effect of unisexual and bisexual sterile releases of Drosophila suzukii on induced sterility. To ensure field-realism, fertile females were wild-F0 freshly emerged from field-collected sweet-cherries; and cage with artificial vegetation and berries were exposed to realistic abiotic conditions. RESULTS: The proportion of fertile females that produced offspring was not significantly different in unisexual and bisexual treatment (45 and 46% respectively). Excluding from the analysis females that had not mated (i.e. no sperm in the spermathecae) had no influence. CONCLUSION: These results suggest the release of sterile females does not always affect the efficacy the SIT. Even though additional phenomena may arise when scaling-up from cages to the field, we conclude that sorting females with genetic-constructs or robotic systems is probably dispensable in D. suzukii SIT, at least when deployed in confined farming systems.