Suppressive effects of insect growth regulators on development, reproduction and nutritional indices of the Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae)

The insect growth regulators (IGRs) chlorfluazuron, flufenoxuron and pyriproxyfen were evaluated, using the leaf-dip technique, on the various developmental and reproductive aspects of Spodoptera littoralis in the parental generation (P), first filial generation (F1) and second filial generation (F2). Additionally, the effect of these IGRs on nutritional indices was also evaluated. The effect on development and reproduction was IGR and generation dependent, with a profound negative impact in the case of the P generation treated with chlorfluazuron. In all treatments, fecundity and fertility increased progressively from the P generation to the F2 generation, and thereby both approached those of the controls. The change in nutritional indices was found to be a function in the candidate IGR and age of the same instar larvae, with a drastic change in late last larval instar (3-day-old 6th larval instar), particularly in the case of treatment with chlorfluazuron. Furthermore, toxicity and morphological deformities induced by the IGRs were reported. The overall results suggest that the IGRs under investigation, particularly chlorfluazuron, interfere with the development process and have the potential for S. littoralis control.