Sublethal Effects of Flufenoxuron, Fipronil and Methoxy-fenozide on Spodoptera litura (Fabricius)

Three insecticides, viz. flufenoxuron, fipronil and methoxyfenozicle, having different modes of action, were evaluated for their chronic effects at sublethal concentrations (LC10to LC25for neonate larvae) on development of second-instar larvae of common cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) by incorporation in semiisynthetic diet. All the three insecticides at 0.5 to 2.5 ppm a.i. have extended the larval life to 30 d compared to only 15 d in control. Cumulative mortality up to pre-pupal stage was 26 to 32% due to flufenoxuron and fipronil and over 70% due to methoxyfenozide. Most of the insects that survived after the prolonged larval stage was dead at the next moult. Twenty-four hours feeding by last-instar larvae on castor leaves, sprayed with sublethal concentration (LC25) of the three insecticides, adversely affected the fecundity and fertility of the moths. Flufenoxuron, fipronil and methoxyfenozide caused 34%, 12.8% and 17.7% reduction in fecundity, respectively. Chronic effect of flufenoxuron is more pronounced on reproductive parameters, especially fecundity.