Division of Entomology, Indian Agricultural Research Institute, New Delhi-110 012 (India).
Ten insecticides were evaluated against the adults of aphid predater, Menochilus sexmaclatus Fabricius, in the laboratory. On the basis of LC50 values, decamethrin, cypermethrin, phosphamidon, malathion and fenvalerate were respectively 10.18, 3.10, 1.97, 1.55 and 1.05 times more toxic than monocrotophos; whereas methyl demeton, endosulfan and lindane were 0.28, 0.04 and 0.02 times less toxic, respectively. The toxicity of nicotine sulphate was very low, the per cent mortality being 40.0 with as high as 1.0 per cent concentration. A comparison of LCso values of various common insecticides in respect of adults of M. sexmaculatus vis-a-vis important aphid pests, viz., Lipaphis erysimi Kalt., Myzus persicae Sulz., and Aphis craccivora Koch indicated that endosulfan, lindane and methyl demeton were relatively safe for the predator. The synthetic pyrethroids despite higher safety margin in some cases as compared to aphid species, still showed very low LC50 values which were much below their recommended concentrations. Hence, their use in aphid management in different crops would disrupt the natural balance.
