Detection of resistance in the blister beetle, Mylabris pustulata Thunb. to various insecticides evaluated during the last quarter century

Relative toxicity of fifteen insecticides to blister beetle, Mylabris pustulala Thunb. adults was determined in the laboratory. hmbdacyhdothrin, aiphamethrin, decamethrin, cypermethrin, fenproprathrin, fenvalerate, pyrethrin, monocrotophos, methyl parathion, malathion, carbaryl, phosphamidon and dimethoate were respectively 356.6, 115.1, 101.6, 39.9, 14.5, 13.2, 12.8, 12.0, 9.4, 6.9, 6.8, 6.5 and 3.4 times more toxk than lindane. A comparison of LC₅₀ values for commonly used and recommended insecticides determined during the last quarter century (1968–1991) revealed a pronounced shift in the level of susceptibility of blister beetle to phosphamidon, malathion and lindane. There was about 18.1, 2.6 and 1.5 times increase in the LC₅₀ values of these inseetkides, respectively. The shift in the level of susceptibility of M. pustuhh to synthetic pyrethroids was much pronounced. Within a short span of nine years (1983–1991), there was 82.7, 63.2 and 19.1 times increase in the LC₅₀ values of decamethrin, cypermethrin and fenvalerate. On the other hand, toxicity of pyrethrin to M. pustuhlo remained more or less the same, the LC₅₀ values being 0.040 in 1983 and 0.059 worked out during 1991. Obviously, response of M. pustulata to pyrethrum did not change significantly. The toxicity of endosulfan remained almost the same as existed nearly quarter of a century ago. The toxicity of other commonly used insecticide carbaryi to M. pustulata did show 3.19-fold resistance after a lapse of about 25 years. Evidence of development of resistance in M. pustulah to synthetic pyrethroids, carbamate, organophosphates and chlorinated hydrocarbons was thus experimentally obtained.