PURSUANCE OF CHEMICAL AND MOLECULAR CHANGES IN EXPOSED COTTON LEAF WORM LARVAE TO CERTAIN INSECT GROWTH REGULATORS

Abstract

The susceptibility of 4thinstar larvae of the Egyptian cotton leafworm, Spodopteralittoralis (Boisd.) to three insect growth regulators IGR’s (teflubenzuron, methoxyfenozide and pyriproxyfen), was evaluated in the laboratory for 10 generations. The fourth instar larvae were treated with various concentrations of three insect growth regulators for 48 h in each generation until F10 and LC50s were calculated after 7 days post treatment in each generation. The obtained results showed that the resistance ratios of selected generations with teflubenzuron, methoxyfenozide and pyriproxyfen were ranged between 1.2709 to 3.0117, 1.2589to 1.9032 and 2.1899 to 4.3675 folds, respectively. Based on the biological aspect, larval durations were increased significantly in the selected generations compared to the control. Pupal durations of S. littoralissignificantly prolonged due to treatment with teflubenzuron, but treatment with methoxyfenozide and pyriproxyfen caused significant decrease.Furthermore, treatments decreased adult emergence, reproductive potential, adult life span and sex ratio. The activities of the measured enzymes after 6 days after treatment of the fourth instar larvae showed up and down pattern through the selected ten generations. The data obtained from the main components showed that treated larvae with teflubenzuron caused significant differences in protein, carbohydrate and lipid contents during selected ten generations, while that treated with methoxyfenozide and pyriproxyfen caused significant decrease in lipid content and elevations in protein and carbohydrate contents. Pyriproxyfen caused reduction in total lipids and total carbohydrate and increase in total protein.Biochemical studies by using electrophoresis patterns displayed different banding patterns of isozymes and total proteins. Oneor more bands were exhibited in untreated larvae in corresponding they were not exhibited in treated larvae. Also, in each selected generation with the three insect growth regulators band expressed by one or more unique or polymorphic one in treated larvae that were different from one to another according to the tested compounds.

Key words: IGR’s– teflubenzuron- methoxyfenozide- pyriproxyfen– Spodopteralittoralis– biochemical studies- protein electrophoresis - enzymes –esterasesisozymes.