Effects of diflubenzuron and penfluron on workers of Apis cerana indica F and Apis mellifera L

Abstract - Newly emerged adult workers of Apis mellifera and A cerana indica tolerated a topically applied dose of 100 μg diflubenzuron (DF) and penfluron (PF) in acetone but the treated bees weighed less than control bees at 2 and 6 d of age. Oral administration of 100 μg DF (as Dimilin 25% wettable powder) in 10 μl sugar syrup proved fatal to A c indica. After 6 d of feeding 50 μg DF, hypopharyngeal gland development, measured as size of acini, was significantly suppressed in both bee species. The suppressed gland development in the treated group could be a consequence of poor gain in weight. Foragers of both bee species readily accepted DF-contaminated sugar syrup and, with increasing doses, there was decrease in time required to consume the contaminated sugar syrup in a dose-dependent manner. The treated bees weighed significantly less than the control bees. Thus, at higher doses chitin synthesis inhibitors may also prove harmful to adult bees.