Andalin, an Insect Growth Regulator, as Reproductive Inhibitor for the Red Cotton Stainer, Dysdercus koenigii (F.) (Hemiptera: Pyrrhocoridae)

Abstract

Effects of different concentrations (0.1%, 0.05%, 0.025%, 0.01%, 0.005% and 0.0025%) of Andalin (Flucycloxuron), an insect growth regulator, were observed on the reproductive system of the red cotton stainer, Dysdercus koenigii (Fabricius). At higher concentrations the fecundity of the emerged females of the treated nymphs was found to be nil whereas at lower concentrations reduction in the fecundity was statistically significant (P?0.01). Comparative anatomical and histological studies of the treated and untreated ovarioles revealed that there was inhibition in the development of ovarioles. The untreated D. koenigii showed normal meroistic-telotrophic ovarioles with large amount of yolk in the oocytes localized in the vitellarium portion. However andalin affected ovarioles showed disrupted structures of the germarium and vitellarium with either complete or partial damage of few or all oocytes. Ultrastructure, under transmission electron microscope, of the untreated ovarioles revealed accumulation of large amount of yolk in the oocytes whereas in case of Andalin treated ovarioles, the yolk was markedly reduced and acquired several vacuoles indicating the resorption of the yolk or reduction in its synthesis. The results demonstrated that Andalin causes rapid cessation of oviposition due to disruption of ovarian structure and inhibition of oocyte growth following topical treatment on 5 instar nymphs of D. koenigii. th