Impact of two insect growth regulators on the enhancement of oxidative stress and antioxidant efficiency of the cotton leaf worm, Spodoptera littoralis (Biosd.)

Abstract

The present study was conducted for evaluating of the impact of two insectgrowth regulators (IGRs) namely, Applaud (buprofezin) as a chitin synthesis inhibitorand Admiral (pyriproxyfen) as juvenile hormone analogue (JHA) in the larval body ofthe cotton leaf worm, Spodoptera littoralis. This evaluation was achieved via (1)Estimating the antioxidant system response present in the 4th larval instar of S.littoralis through estimating the activity of two enzymes; catalases (CAT) andglutathione-S-transferase (GST), as well as an antioxidant compound; glutathionereduced (GSH). (2) Estimating the accumulated lipid peroxidation in the larvaltissues by evaluating the level of Malonaldehyde (MDA) as an indicator for lipidperoxidation. Both tested IGRs used in this study showed more or less similar trend intheir mode of action relative to the tested biomarkers in the present work. CATshowed a significant increase in its activity (42.02%) and (139.26%) for buprofezinand pyriproxyfen, respectively. This activity lasts for only one day post treatment thenit was inhibited to be very close to that level in normal untreated larvae. This may bedue its consumption in scavenging reactive oxygen species (ROS) produced due tosignificant accumulation of MDA. One the other hand, GST showed persistedincrease in its activity especially with buprofezin treated larvae may be to overcomethe deleterious effect of accumulating MDA. Similarly, GSH which serves as a freeradicals scavenger also showed a significant increase in its level especially due totreatment. The present study which is conducted for the first time, documented theoccurrence of lipid peroxidation due to IGRs treatment in the larval tissues in S.littoralis larvae which enhanced different antioxidant defensive system to overcomeits effect.