Abstract
Article History Resistance levels in laboratory and field strain of Spodoptera littoralis (Boisd.) against two IGR's (lufenuron and tebufenozide) were studied. Resistance levels were higher in fayoum than Sharkia and laboratorystrain, in the two IGR's. There was a positive correlation between resistance and Alkaline phosphatase and α-esterase enzyme, while there was negative correlation between resistance level and Acid phosphatase & trehalase activity, while in amylase enzyme Fayoum strain was lower than Sharkia and laboratory strain. Fayoum strain showed higher activity in case Invertase enzyme than other two strain.
Highlights
Spodoptera littoralis is a pest of econamic importance in Egypt, where cotton is infested during May-July following migration from previous host plant clover Trifolium alexandrinum. Ishaaya and Klein (1990) found that, Spodoptera littoralis larvae collected from a cotton field that was heavily sprayed with conventional insecticides showed strong resistance to organophosphates and pyrethroids and a mild tolerance to benzoylphenylureas
MATERIALS AND METHODS Insects: A laboratory strain of the cotton leaf worm Spodoptera littoralis was obtained from the Central Agricultural of Pesticide Laboratory that established under constant conditions of 25°C ± 1 and 70 ± 5 % R.H. and out of any contamination with chemicals till the time of study
Compounds: Match® (Lufenuron) is an acylurea insect growth regulator which inhibits chitin synthesis and thereby prevents Lepidoptera larvae from molting from one stage to another
Summary
Spodoptera littoralis is a pest of econamic importance in Egypt, where cotton is infested during May-July following migration from previous host plant clover Trifolium alexandrinum. Ishaaya and Klein (1990) found that, Spodoptera littoralis larvae collected from a cotton field that was heavily sprayed with conventional insecticides showed strong resistance to organophosphates and pyrethroids and a mild tolerance to benzoylphenylureas. IGR’s differ widely from the commonly used insecticides, as they exert their insecticidal effects through their influence on development, metamorphosis and reproduction of the target insects by disrupting the normalactivity of the endocrine system (Oberlander, etal., 1997).Insect growth regulators (IGR’s) received great attention as a hope for the future of insect control because of their mode of action which is different from conventional insecticides Among these IGR’s, Tebufenozide (mimic) belongs to a class of insect growth regulators (IGRs), bisacylhydrazine ecdysteroid agonists, mimicking the natural insect moulting hormone 20-hydroxyecdysone (20-E) (Dhadialla, et al, 1998).Lufenuron (Match) is an acylurea insect growth regulator which inhibits chitin synthesis by prevents Lepidoptera larvae from molting from one stage to another. These compounds interfere with cutical deposition, by the inhibition of chitin synthesis (Riddiford and Truman,1978).The intensive use of broad-spectrum insecticides against S. littoralis has led the development of resistance to many registered pesticides for its control (Aydin and Gurkan, 2006) including IGRs (Temerak, 2002)
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