The effects of mosquito larvicides and adulticides applied via truck-mounted and aerial spray on western honey bees (Apis mellifera) in Florida, USA

The use of ultra-low volume (ULV) mosquito adulticides is common in Florida, USA, as ULVs are highly effective at controlling mosquitoes. Furthermore, many Florida mosquito control district personnel treat water bodies with mosquito larvicides. Currently, not much is known about how exposure to these chemicals in realistic field scenarios will impact overall honey bee colony strength. In this study, we determined the impact of field-realistic mosquito control practices on colony strength parameters by placing 15 honey bee colonies in three treated sites (five colonies per site) where mosquito control operators treated three to five times over three months. We also placed 15 colonies in three sites (five colonies per site) receiving no mosquito treatment applications (negative control sites). At the treated sites, Mosquitomist Two U.L.V.®, Naled®, and Vectobac12AS® in various combinations and timepoints were applied for mosquito control. Colony strength parameters were measured before and after the three-month evaluation period. Pollen, honey, adult bees, and brood were collected from all hives and analyzed to determine the residue levels of mosquito control products present in the hives. Mosquito control product residues were found at low concentrations in all sampled hive matrices across all treatments (ranging from 0.03 to 70.99 ng/g). No significant differences were observed in mortality or strength parameters between colonies located in treated and control sites, neither was a direct impact of a spray event observed on adult bee mortality. The resulting data can be used to inform future best management practices for mosquito control programs and apiculture.