Effect of Host on the Susceptibility of Lipaphis erysimi (Kaltenbach) to Insecticides

Mustard aphids were reared on yellow sarson, brown sarson and Indian mustard during 2001 and 2002 and the effect of host on the susceptibility of aphid to insecticides was estimated by comparing LC_so values. The susceptibility to endosulfan was governed largely by the host as the aphids reared on B. campestris var. yellow sarson were found 9.93 and 4.76 times more susceptible to endosu1fan than those reared on brown sarson during 2001 and 2002, respectively. Deltamethrin was most toxic with LC₅₀ value 0.000052% to aphids on B. juncea population among all the tested insecticides. The aphids from B. juncea were most susceptible to deltamethrin, methyl-O-demeton during 2001 and to monocrotophos during 2002. The aphids of yellow sarson were most susceptible to endosulfan and monocrotophos in 2001, while the population from the same host was most susceptible to deltamethrin, methyl-O-demeton and endosulfan in 2002. Difference in toxicity of an insecticide against a particular insect species feeding on different host indicate that the host plant on which the insect feeds played an important role in governing the toxicity of the chemical.