Joint action of certain insecticides by sub lethal dose effect on the cotton leafworm spodoptera littoralis (lepidoptera : noctuidae)‎ larvae

الملخص EN

Toxicity of the four compounds belong to different groups of insecticides: indoxicarb, imidacloprid, pyridalyl and lufenuron against the 2nd and 4th larval instars of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) .

The joint toxic action of lufenuron with tested compounds against 2nd instar larvae S.

littoralis was studied.

The activities of polyphenol oxidase (PPO) and chitinase were also studied.

Indoxicarb against 2nd and 4th larval instars (LC50 = 0.087 and 0.31 ppm, respectively) was more toxic than lufenuron (LC50 = 0.23 and 0.62 ppm, respectively), followed by imidacloprid (LC50 = 0.93 and 1.23 ppm, respectively) and pyridalyl (LC50 = 1.28 and 3.13 ppm, respectively) after 96 hours of treatment.

Lufenuron/ indoxicarb mixtures resulted in potentiation effect more than the lufenuron/imidacloprid mixtures and lufenuron/pyridalyl mixtures respectively, the co-toxicity factor (CTFs) gave potentiation effect with three mixtures tested, the CTF ranged from +62.6 to +20.

The in vivo interaction of LC25 values of each tested compounds, with polyphenol oxidase (PPO) and chitinase caused significant increase in the activities in all treatment.

Therefore, mixtures of lufenuron with these tested insecticides can be used for cotton leafworm control.

The results generally indicate that indoxicarb, imidacloprid and pyridalyl are a successful insecticides at sub lethal dose, which may be used to prevent or delay appearance of resistance to conventional pesticides and save the environment.