The house fly, Musca domestica, is a very significant pest due to transmitting of various human and

animal pathogenic diseases. In a response to environmental threats of chemical insecticides, toxic

and biochemical effects of a relatively new plant extracts of willow (Salix aegyptiaca L.) and chasteberry (Vitex agnus-castus L.) comparing with NeemAzal T/S were studied on 3rd larval instar of M. domestica. Results showed that NeemAzal T/S is highly toxic to 3rd larval instar with LC50 and LC90 of 0.009 and 0.098 µg mL-1, respectively. Whereas, willow and chasteberry showed low toxic effects comparing with NeemAzal T/S with LC90 of 70.048 and 66.698 µg mL-1, respectively. Concentrations of total protein markedly decreased in 3rd larval instar after 24 hours exposure to NeemAzal T/S, willow and chasteberry with no significant effects on total lipids compared with control. NeemAzal T/S, willow and chasteberry significantly decreased ALT activity, but NeemAzal T/S only markedly decreased AST activity. On the other hand, amylase (EC3.2.1.1) significantlyincreased due to exposure to all tested substances with only significant increase in invertase (EC 3.2.1.26) activity due to exposure to chasteberry. Larval exposure to NeemAzal T/S, willow or chasteberry showed normal trehalase (EC 3.2.1.28) activity as control. These findings show that willow and chasteberry can cause marked toxic effects on larvae of M. domestica as well as NeemAzal T/S, which suggesting that more studies on insect development using these plant extracts could be useful