INFLUENCE OF FOLIAR FERTILIZERS ON THE TOXICITY AND TOLERANCE TO SOME INSECTICIDES IN THE COTTON LEAFWORM

The joint action of 2 pyrethroid insecticides with several foliar fertilizers against the 4th-instar larvae of Spodoptera littoralis was determined. The rate of development of tolerance throughout 3 successive generations to insecticides alone and their combinations with fertilizers was also assessed. The toxicity of the insecticides tested was greatly enhanced by using fertilizers in admixture with each of them. The inclusion of such fertilizers in spray emulsions slows down the development of tolerance to both insecticides. The synergistic action of fertilizers and the decrease in the induction of tolerance to insecticides can be attributed to the presence of inorganic ions and to decreasing the pH of both acidic experimental insecticides resulting in increasing the penetration rate of the internal membranes of the cotton leafworm.