Effect Of Pre-Treatment Of Synergists On The Toxicity Of Insecticides To Spodoptera Uitura (Fabricius)*

The pre treutment of different synergists before the application of insecticide proved synergistic over the period of time (up to 24hr). The toxicity of cypermethrin,when pre- treated with different synergist showed wide variation in mortality of Spodoptera litura larvae. The highest mortality of 83.33% was observed/i when pipronyl butoxide (PBO) was applied 8hr before the application of cypermethrin. PBO, dillapiole and dihydrodillapiole increased more than 50% fenvalerate induced mortality from 2–14, 6–14 and 4–8 hr, respectively at post-treatment. The highest mortality of 80% by lambda cyhalothrin was observed at 6 and 8 hr post-treatment of PBO and dihydrodillapiole. The toxicity of profenophos increased with pre-treatment of each of the synergists. The highest mortality of 70% and 76.67% was observed at 8 and 10 hr post-treatment of dillapiole and PBO respectively. The mortality obtained between 6 to 12 hr pretreatment of I'BO, and dillapiole varied from 53.33 to 70% and 63.33 to 46.67%. There was a highly significant increase in the mortality due to cypermethrin, fenvaleratc, lambda-cyhalothrin and profenophos when pre-treatment at 6 to 10 hrs with PBO was done. A delay of 8–10 hr prior to insecticide application was beneficial in case of dihydrodillapiole whereas a delay of 6–14 hr following pre-treatment of dillapiole increased the synergistic effects with various insecticides.