Biochemical Analyses of Action of Chlorfluazuron as Reproductive Inhibitor in Spodoptera litura

Abstract

Chlorfluazuron is highly effective against insect pests because it disrupts chitin synthesis during the moulting process (Retnakaran et al., 1989) and causes malformed larvae in Spodoptera litura (Omatsu et al., 1991). Chlorfluazuron had been used as chitin synthesis as well as reproductive inhibitor (Perveen, 2006). Toxicity and effects of chlorfluazuron on reproduction and viability of S. litura had been examined. The LD50 was found to be 12.0 ng larva-1 when evaluated up to pupation and 9.9 ng larva-1 up to adult emergence. Lethal dosages of chlorfluazuron when applied to newly-ecdysed fifth instars had a devastating effect on the S. litura population by killing them during larval, pupal, and adult stages. Reduction in the body weight was also observed in the larvae and pupae when treated with a sublethal dose (LD30: 3.75 ng larva-1) and in the adults when treated with sublethal doses (LD10: 1.00 ng larva-1; LD30: 3.75 ng larva-1) as newly-ecdysed fifth-instar larvae of S. litura, although the number of matings per female and life span of adult females and males remained unaffected by the same treatments. In insect pest management, the purpose of research is to maintain the pest population below a level of economic loss. Topical application of sublethal doses of chlorfluazuron (LD10 or LD30) on newly-ecdysed fifthinstars did not kill the whole population of S. litura but reduced it, by affecting its reproduction. When sublethal doses were applied only to females or only to males, or both sexes, the results from these observations suggest that the fecundity was reduced to a similar degree when only females or only males or both sexes were treated with LD10 or LD30 doses as newly-ecdysed fifth-instars. However, the fertility and hatchability were affected more when only males were treated with LD10 and much more when treated with LD30 (Perveen, 2000a). However, there were no significant differences observed between larval and pupal treatment in the reduction of these biological parameters (Perveen, 2009a). Effects of chlorfluazuron on ovarian development and oogenesis (Perveen and Miyata, 2000), testicular development and spermatogenesis (Perveen, 2000b), insemination and number of inseminated sperm (Perveen, 2008) and haemolymph-borne ovipositionstimulating factors (Perveen, 2009b) in S. litura had been reported. The effect of sublethal doses of chlorfluazuron on embryogenesis of S. litura has also been reported during the