Effects of azadirachtin on the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae)

Effects of sublethal azadirachtin exposure to the biological performance of Tetranychus urticae Koch was studied under laboratory conditions. Bioassay was used to asses the effect of different concentrations of azadirachtin on longevity, fecundity, fertility, and offspring development. Azadirachtin (64 and 128 ppm) affected fecundity and mortality but had no effect on fertility and offspring development. A subsequent life-table study with 80 ppm of azadirachtin found that the compound caused a reduction of 50% in survival to adult stage. The peak of reproduction was reached at 5 days causing a decrease in the mean fecundity to almost eight times than of untreated females. The net reproductive rate (R-O), the intrinsic rate of increase (r(m)),,J, and the finite rate of increase (lambda) of treated females were lower. Treatment showed a negative value of r(m) resulting in a declining population. These results suggest that azadirachtin could be incorporated in Integrated Pest Management (IPM) programmes of T. urticae.