Relative Toxicity of Insecticides on the Population Of Whitefly Bemisia Tabaci (Gennadius) (Hemiptera: Aleyrodidae) from Cotton and Leucaena

The whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) from leucaena and cotton were studied with adult leaf dip bioassay for evaluating toxicity of some currently used insecticides. These revealed that imidacloprid is the least toxic when compared to acetamiprid, acephate and cypermethrin. Relative toxicity ratio between the populations when compared, cypermethrin exhibited 14 fold higher values in cotton populations than those of leucaena; among the neonicotinoids, acetamiprid exhibited 14 folds while for imidacloprid it was only 5 fold higher; and acephate exhibited 11 fold higher ratio in cotton populations than of leucaena. The effectiveness of the insecticides on the basis of toxicity index value is as follows; Cypermethrin 〉 acetamiprid 〉 acephate 〉 imidacloprid, for leucaena populations while it is cypermethrin 〉 acephate 〉 acetamiprid 〉 imidacloprid for the cotton populations.