TOXICITY OF DIFLUBENZURON AND PENFLURON TO IMMATURE STAGES OF APIS-CERANA-INDICA F AND APIS-MELLIFERA L

Diflubenzuron (DF) and penfluron (PF) in acetone were found to be equally toxic to Apis mellifera and A cerana indica in topical application tests based on equivalent body weights. Toxicity resulting from median lethal dosage was highest for pupae and was lower for IV and III instar larvae. Acetone proved lethal to eggs, I and II instar larvae. There was no delayed lethal and morphological effect of the treatment on larvae, but some adult bees, treated in the same manner as pupae, showed morphological abnormalities, such as crumpled wings and poor interlocking at stylet and lancets of the sting apparatus. Feeding of 50 mg DF to small experimental colonies of both bee species enhanced egg laying but significantly reduced the amount of unsealed and sealed brood within 10 days of treatment.