Sublethal Effects Of Selected Pyrethriods On The Cotton Bollworm Helicoverpa Armigera

The applications of insecticides and natural enemies are two main measure for insect pest control,but inharmonious conflicts sometimes occour between the chemical and biological control.The sublethal effects of 4 insecticides (beta-cypermethrin, fenvalerate, fenpropathrin and deltamethrin) on the cotton bollworm were investigated from their biology and physiology for meeting the practical needs and coordinating the chemical and biological control. The toxicity of these 4 insecticides to the cotton bollworm was deltamethrin>fenpropathrin > beta-cypermethrin > fenvalerate,the LC50s were 9.89,30.30,561.63 and 6956.26mg/L. The resulted showed all the insecticides had no-choice antifeedant acticity, the content consumed by those treated were lowed than those of untreated on the 24th hour.And that of those treated with LC50 sublethal concentration had significant differences with control till the 48th hour post-treatment. The sublethal concentration of insecticides inhibited the development and weight of H. armigera,especially to those treated with beta-cypermethrin. All the insecticides had deleterious effects on the number of larvae surviving to pupae and the number of pupae surviving to adulthood.The development duration of those treated with pyrethriods prolonged.The sublethal concentration caused latent toxicity, deformed pupae and deformed wings in the adults.The accumulative oviposition of cotton bollworm decreased, and the differences were significant based on statistic analysis. The treatments of the sublethal doses(LC50) of 4 insecticides increased the specific activities of glutathione s-transferases (GSTs) and esterase (CarE) While they all inhibited Na+-K+-ATPase activity.However,there were different changes of the quality and quantity of specific activities of enzyme in the susceptible strain of cotton bollworm according to different insecticides.