Evaluating the Toxicity of Known Western Honey Bee-Safe Insecticides in Controlling Small Hive Beetles (Aethina tumida)

Currently, there is no integrated pest management approach for controlling small hive beetles (Aethina tumida), a widespread honey bee (Apis mellifera) pest. To date, only hive trapping has shown any effectiveness in controlling the pest. In this study, we tested several possible active ingredients that have been shown previously to demonstrate low toxicity towards honey bees. To test their toxicities, we treated both SHBs and honey bees topically and exposed SHBs to these compounds orally via pollen. Coumaphos (industry standard), a solvent control (acetone), and a positive control (dimethoate) were used for comparisons. Thiacloprid (LD50 = 1.3 ng/SHB; LC50 = 12 µg/g pollen) was the most toxic active ingredient tested against SHBs both topically and through pollen. Topically, thiacloprid was 340× more toxic to SHBs than coumaphos (LD50 = 431 ng/SHB). However, acetamiprid (selectivity ratio = 152) was much more toxic to SHBs than to honey bees compared to thiacloprid (selectivity ratio = 3). These findings demonstrate the need to find other active ingredients other than coumaphos and that acetamiprid has the greatest potential to reduce SHB populations safely in a honey bee hive. Field research using acetamiprid should be conducted to explore possible sub-lethal effects on honey bees.