Effects of abamectin and
hematoporphyrin (HP), eco-friendly insecticides, on the
concentration of the oxidative stress indicator malondialdehyde (MDA) and on
the antioxidant enzymes; catalase (CAT), glutathione-S-transferase
(GST); activity were studied in the 4^th instar larvae of Spodoptera
littoralis (Biosd.). There effects on glutathione (GSH) level were also
investigated. MDA content was significantly increased on the 1^st day
post treatment of both insecticides, but increased significantly only with HP
treatment on the 5^th day of treatment. Abamectin treatment decreased
GSH significantly on the 3^rd and 4^th days, while HP
treatment increased its level on the 1^st and ^2nd day post
treatment.  Activities of antioxidant
enzymes, CAT and GST, did not show a consistent pattern with respect to
abamectin and HP. These results suggest that exposure to abamectin and HP
resulted in impaired enzymatic antioxidant defense capacity in 4^th
instar S. littoralis larval tissues.