Gossypol as a Natural Insecticide in Cotton Plants against Cotton Thrips and Pink Bollworm

Gossypol level plays an important role in self-protection as antibiosis of cotton plants (Gossypium spp.). Thus, it was found necessary to evaluated the level of gossypol in the different parts during the stages of growth of cotton plant for three cotton cultivars viz., Giza 86, Giza 80, and Giza 45. Their performance against cotton thrips, Thrips tabaci and pink bollworm, Pectinophora gossypiella under field conditions was studied. Statistical analysis revealed that there was a positive correlation between the gossypol content in the seed pulp of different varieties of cotton and the amount of gossypol detected in the different parts of the produced plants. The level of gossypol in seeds were significantly higher on Giza 86, and Giza 45 having 1.90% and 1.52%, respectively, whereas the level of gossypol was limited in Giza 80 (1.45%). Therefore, cotton variety, Giza 86 showed higher levels of gossypol in all parts of plant. In field tests during 2019, the results indicated that the higher content of gossypol had a negative effect on population size both T. tabaci (adult and nymph) and P. gossypiella larvae that infested cotton bolls. Cotton thrips and pink bollworm population exhibited negative response to gossypol content. According to the results, the cotton varieties could be arranged in the following descending order concerning their susceptibility to infestation with these pests: Giza 80, Giza 45 and Giza 86.