Evaluating the impact of oxalic acid vaporization on drone honey bee (Apis mellifera) reproductive health

The annual Bee Informed Partnership national survey of U.S. beekeepers consistently identifies queen failure as a top three colony stressor. Although often overlooked, drone health directly impacts queen productivity and longevity. To date, there have not been any studies on the effects of oxalic acid vaporization on drone larvae. The purpose of this study is to evaluate the effect of oxalic acid, a widely used organic miticide, on drone reproductive health when applied via vaporization during the late larval stage. In May 2023, fifteen honey bee colonies were requeened with sister queens of European-derived honey bee stock and equalized before a plastic drone foundation frame was placed inside. Three colonies were randomly assigned to one of five treatment groups. Three groups were treated with varying oxalic acid doses at 1g, 2g, and 4g per brood chamber, and two groups served as the controls being treated with ice (negative control) and Apivar® (positive control). The oxalic acid was vaporized using the commercially available InstantVap®. Six to nine-day old drone larvae were exposed to their respective treatments. Drone mortality was measured and the surviving drones were marked at emergence with paint markers and allowed to reach sexual maturity in the colony. They were collected 20 d post-emergence for lab analysis. Data was collected on drone weight, semen volume, sperm cell count, and sperm motility. This study will be useful for beekeepers, particularly queen breeders, who are interested in producing high-quality drones.