Oral toxicity of some commonly used pesticides to workers of Apis cerana F. and Apis florea F.
1983
Weerawan Amornsak | Pongthep Akratanakul (Kasetsart Univ., Bangkok (Thailand). Faculty of Agriculture. Dept. of Entomology)
Commonly used farm chemicals were tested for determining their oral toxicity against workers of the native honey bees, Apis cerana F. and Apis florea F. The tested chemicals were chlorinated hydrocarbon insecticides (dieldrin 100 %, dieldrin 50 % W.P., dieldrin 18 % E.C., endosulfan 35 % E. C.): organophosphorous insecticides (methyl parathion 80 %, methyl parathion 50 % E.C., dimethoate 30 % E.C., monocrotophos 56 % W.S.C.): carbamate insecticides (carbaryl 99 %, carbaryl 85 % W.P., methomyl 90 % W.D., methomyl 18 % W/V): and herbicides (2,4-D and paraquat). The tested herbicides had relatively low level of toxicity to workers of the two honey bee species. Among the tested chemicals, monocrotophos showed the highest degrees of toxicity to both. A. cerana and A. florea. Different responses to different insecticides were found between the two honey bee species. Whereas methyl parathion was found to be second only to monocrotophos in its toxicity to A. cerana, for A. florea dieldrin was proven to be more toxic than methyl parathion. Furthermore, workers of A. florea showed a relatively higher level of resistance to carbaryl than those of A. cerana, although the body weight and size of A. florea workers were much smaller. These findings challenge the commonly established theory that the larger the body size of the bees, the higher degrees of resistance to insecticides.
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