Effects of sublethal concentrations of fenitrothion on beet armyworm (Lepidoptera: Noctuidae) development and reproduction

We present data on the effects of various concentrations of the organophosphorus insecticide, fenitrothion, on development, reproduction and eggshell structure of Spodoptera exigua. The insecticide did not change the male/female ratio in tested populations. The pesticide-exposed larvae were significantly smaller than the controls and their pupation was delayed. These changes were not proportionally concentration-dependent. After imaginal molting experimental females laid significantly fewer eggs than controls. This effect was the same whether one or both members of a mating pair were exposed to fenitrothion during the larval stage. In the egg stage the insecticide caused serious malformations of the eggshell. The exposure caused other types of clearly abnormal development of eggs: two micropylar regions were noticed. Hence, even a low concentration of fenitrothion in the diet can lead to serious disturbances in reproduction and thus possibly at the population level.