carbaryl,cypermethrin and mevinphos were applied at the rates of 0,5,10,20 and 40 ppm on hydrilla at department of entomology all insecticides had the effects on its growth. the plant was rotted and died within 3 days at the rate of 40 ppm ofcypermethrin and mevinphos. the water after applied with three insecticides at every rates were turbiness on the 1 day and after the 2 daythe solution began to sattle.