INFLUENCE OF OVERWINTERING LARVAL DIAPAUSE ON SUSCEPTIBILITY OF Pectinophora gossypiella (SAUNDERS) (LEPIDOPTERA: GELECHIIDAE) TO SEVERAL INSECTICIDES

To investigate the effect of overwintering larval diapause on the susceptibility of pink bollworm, Pectinophora gossypiella (Saunders) to various insecticidal classes (lambda-cyhalothrin, chlorpyrifos, methomyl, emamectin benzoate and spinetoram), laboratory bioassay tests were achieved on diapaused, rosetted and susceptible larval strains. The two field strains were collected from the infested cotton plants cultivated at different localities of Sharkiya Governorate during 2012 and 2013 seasons. The results indicated that the susceptibility ratios of the rosetted cotton flowers strain/ the diapaused strain (R/D) were varied between the two field strains of P. gossypiella, and among the insecticides tested as well, they ranged between 0.58 fold in case of spinetoram and 7.47 fold in case of lambda-cyhalothrin. The data also revealed that the newly hatched larvae descended from rosetted cotton flowers were more resistant to methomyl (121.52 fold) and lambda-cyhalothrin (43.57 fold) than the newly hatched larvaedescended from overwintering diapause. The two field strains showed an equal susceptibility ratio in case of chlorpyrifos(28.53 and 28.81). The rosetted larvae were more susceptible to spinetoram than the diapaused larvae. While diapaused strain was more susceptible to emamectin benzoate than other two strains.