Are insect growth regulators ineffective at controlling a honeybee pest? Experimental evidence from the small hive beetle (Aethina tumida)
The small hive beetle (SHB), Aethina tumida, is an invasive honeybee parasite native to sub-Saharan Africa, and it is thought to be a contributing factor of Colony Collapse Disorder (CCD) in commercial honeybees (Apis mellifera). Adult beetles lay their eggs within a hive, and hatched larvae destroy the hive by tunneling through the comb and eating bee brood and honey and pollen stores. Effective management of these invasive pests is important for beekeepers and consumers, alike. Insect growth regulators (IGRs) are chemical compounds that interfere with the normal development of insects, which have been successful in controlling a variety of insects, including other beetle species. Two such IGRs, hydroprene and azadirachtin, were experimentally examined in the laboratory as a potential control for SHB. Newly hatched larvae were fed diets that contained 0.1, 1.0, 10, or 50 ppm of hydroprene-laced food, and 0.1, 1.0, or 10 ppm of azadirachtin-laced food. The larvae were then monitored throughout their growth and metamorphosis into adults to gauge any deleterious effects of the IGRs.
In all treatments, both hydroprene and azadirachtin proved ineffective at controlling SHB larvae, and nearly all larvae survived to adulthood with no significant differences in adult emergence across treatments. Our results suggest that these two IGRs, orally administered in the tested concentrations, are not viable solutions for SHB control. These preliminary studies provide insight into future avenues of research, which will hopefully help beekeepers and farmers prevent and control SHB infestations in commercially important honeybee colonies.