The insecticidal effects, specifically, changes in hemolymph total protein and malondialdehyde (MDA) levels, and antioxidant enzyme activities of azadirachtin (AZA) given to the wax moth, Galleria mellonella L. (Lepidoptera: Pyralidae) larvae via force feeding were investigated. Bioassays showed that the LD50 and LD99 (lethal dose) values of AZA were 2.1 and 4.6 μg/larva, respectively. Experimental analyses were performed with five doses of AZA (0.5, 1, 1.5, 2, and 3 μg/larva). Total protein level in larval hemolymph increased at all AZA doses at 24 h whereas a considerable decrease was observed at 2 and 3 μg/larva doses, and only an increase displayed at 1.5 μg/larva at 72 h. The level of MDA increased at 2 and 3 μg/larva doses at 24 h compared with controls. This trend was also observed at 1.5, 2, and 3 μg/larva doses at 72 h and MDA levels were lower when compared with those of 24 h at all doses except for 1.5 μg/larva dose. Catalase activity decreased at 1, 1.5, and 2 μg/larva doses at 24 h whereas increased at all doses except for 0.5 μg/larva at 72 h compared with controls. AZA led to a decline in superoxide dismutase activity at all experimental doses at 24 and 72 h except for 3 μg/larva doses at 72 h. An increase in glutathione-S-transferase (GST) activity was evident at all AZA doses at 24 h. AZA displayed 68% decline in GST activity at 72 h post treatments when compared to 24 h. Consequently, We infer that the toxicity of AZA extends beyond its known actions in molting processes to redox homeostasis.

Azadirachtin (AZA), a plant allelochemical, is used against pest organisms and Lepidopteran species are quite sensitive to this substance. In this study, the developmental effects of AZA on model insect and greater wax moth, Galleria mellonella L. (Lepidoptera: Pyralidae) larvae via force feeding method were investigated. To investigate the effects of different doses of pure AZA (0.2-5 µg/larva), seventh instar larvae were fed by a force feeding method. The results showed that all doses of AZA caused lethal and sublethal effects on the biological parameters of G. mellonella. Larval developmental time increased while that of pupa did not change depending on the increasing doses of AZA. In addition, adult longevity, and weights of pupae and adults decreased at all AZA doses in a dose-dependent manner. In conclusion, this study, using G. mellonella as a model organism, showed that AZA has insecticidal activity and causes adverse effects on the life history traits of Lepidopteran pest insects.