The side effects of azoxystrobin (Amistar, 25% SC) and tebuconazole (Toledo 43% SC) fungicides on some biological aspects of Egyptian cotton leaf worm (ECLW) (Spodoptera littoralis, Boisd.) were investigated in comparison with the untreated control under laboratory conditions. The fourth instar larvae were fed for 24 hrs on castor bean leaves (Ricinus communis L.) treated with different concentrations of the tested compounds. Food consumption was measured regularly throughout the feeding tests until pupation. The results clearly indicated that the two fungicides reduced the weight consumed leaves larva-1 and decreased the feeding ratio. The azoxystrobin fungicide was more effective than tebuconazole especially at higher concentrations. Both compounds reduced larval weight and increased larval mortality and larval durations (days). Furthermore, reduced pupation % and adult emergence, and increased pupal durations. These compounds reduced reproductive parameters of adults (fecundity and fertility) and increased sterility %. The longevity of males and females was reduced.
The present study revealed that, in all cases, the toxic effects of azoxystrobin and tebuconazole on some biological aspects of the Egyptian cotton leaf worm were proportionally increase with the increase of the concentrations. The results clearly indicated that the azoxystrobin fungicide was more effective than tebuconazole on Egyptian cotton leaf worm (ECLW).