Chemosterilant activity of naturally occurring quinones and their analogues in the red cotton bug, Dysdercus koenigii (Het., Pyrrhocoridae)

The chemosterilant activity of two naturally occurring napthaquinones, plumbagin from Plumbago sp. and juglone from Juglans regia has been evaluated using the red cotton bug Dysdercus koenigii. Their activity were compared with synthetic napthaquinones, menadione, two benzoquinones, 2,6-dimethyl and 2,3,6-trimethylbenzoquinone and a hydroquinone 2,6-dimethylhydroquinone. As far as the authors are aware, the present investigation is the first systematic attempt to investigate the effects of quinones on different aspects of reproduction, namely mating behaviour, fecundity and fertility. All the above types of quinones have revealed adverse effects on the reproduction of D. koenigii, which were topically treated as 1-day-old adults with different doses of the compounds depending on their 50% lethality (LD 50 ) values. Analysis of the data revealed a highly statistically significant reduction in the number of eggs, their hatching and further development up to the final instar stage. The sterility index increased with the increase in the dose of any of the above compounds and was highest when both sexes were treated. Among the natural products, juglone induced more sterilizing effects than plumbagin at 5-10 μg/insect. Menadione caused sterility at a very low dose such as 0.5 μg. Of the two benzoquinones, the dimethylbenzoquinone acted at a much lower dose.