Field Efficiency of Humic Substances, Boric Acid and some Novel Insecticides against Aphis gossypii Glover and Bemisia tabaci (Gennadius) on Cotton Plants

Abstract

Nutritive acids improve the plant growth via increasing its carbohydrates content and nutrients uptake, and enhance the plant resistance to biotic and a biotic stress factors. Accordingly, field experiments were conducted at Sakha Agricultural Research Station, Kafr EL-Sheikh Governorate, Egypt during seasons 2016 and 2017 to evaluate the insecticidal activity of the nutritive acids (boric acid, humic acid and fulvic acid), pymetrozine, dinotefuran and thiamethoxam against Aphis gossypii Glover and Bemisia tabaci (Gennadius) on cotton plants under the field conditions. The toxicity of the binary mixtures of the nutritive acids with the tested insecticides against the two insects was evaluated as well. The tested compounds were applied at their field recommended rates. Pymetrozine, dinotefuran and thiamethoxam applied separately exhibited high efficiency against A. gossypii (causing 90.10 – 97.48% reduction), B. tabaci adults (recording 88.07 – 94.68% reduction) and B. tabaci immature stages (producing 87.29 – 92.43% reduction). Boric acid, humic acid and fulvic acid resulted in a considerable toxicity to both A. gossypii (31.60 – 55.21% reduction) and B. tabaci adults (29.51 – 43.70% reduction) and immature stages (22.46 – 37.94% reduction). Among the tested nutritive acids, humic acid proved to be the most potent against A. gossypii, while fulvic acid was the most effective on B. tabaci. Binary mixtures of the nutritive acids with the tested insecticides resulted in insignificant changes in the insecticides activity against the two pests. These results suggest that boric acid, humic acid and fulvic acid could be effectively used to improve the cotton plant growth (as recommended) and, at the same time, to control A. gossypii and B. tabaci. Further studies are required to clarify the mode of action through which the nutritive acids cause their insecticidal activity against sucking insects on cotton plants.