Susceptibility of the small hive beetle, Aethina tumida (Coleoptera: Nitidulidae), to insecticides and insect growth regulators

The small hive beetle, Aethina tumida Murray, has become an important pest of the honeybee, Apis mellifera L., in the USA. In this study, we assessed the susceptibility of this pest to 14 selected insecticides and four insect growth regulators (IGRs). The results indicated that the small hive beetle (SHB) was selectively susceptible to several classes of insecticides. The lethal concentration for 50% mortality (LC50) to adult SHBs was 0.53, 0.53, and 0.54 mu g/vial for fenitrothion, chlorpyrifos, and methomyl, respectively. However, against the larval stage, fenitrothion was the most toxic with an LC50 of 0.89 mu g/vial. Chlorpyrifos had an LC50 of 1.64 mu g/vial which was similar to the LC50 of 1.21 mu g/vial for fluvalinate and 2.24 mu g/vial for methomyl. Overall, these insecticides were found to be more toxic to SHBs than the organophosphate coumaphos which is currently used for control of SHB populations. Among the IGRs tested, fenoxycarb and methoprene were the most effective on early instar larvae with an LC50 of 30.20 and 61.89 mu g/vial, respectively. None of the IGRs were found to adversely affect the development of third-fourth instar larvae of the SHB. The susceptibility of the SHB was also assessed in soil bioassays, and the patterns of responses were similar to those reported with the glass-vial bioassays. Our data provided useful insights and baseline in the development of an effective pest management strategy for the SHB in honeybee colonies. However, these pesticides should be used in a way that minimizes honeybee exposure and meets safety requirements for human consumption of honey products.