Ovicidal action of some newer insecticides against eggs of Eublemma amabilis—a lepidopteran predator of Indian lac insect, Kerria lacca (Kerr)

摘要

The lepidopteran predator of lac insect, Eublemma amabilis Moore is a serious threat to lac insect culture all over the country where lac cultivation is in practice. Laboratory evaluation of four insecticides viz., indoxacarb, spinosad, fipronil and ethofenprox at different concentrations was carried out for assessing their ovicidal action against one day old eggs of E. amabilis. The ovicidal effect of insecticides has been assessed by dipping the egg masses in an insecticidal solution. The insecticides evaluated have shown varying degrees of ovicidal action to E. amabilis. The egg inhibition activity amongst different treatments varied from 1.71-67.15% with the treatment of indoxacarb, 36.82-75.44% with fipronil, 81.61-100% with spinosad and 82.02-100% with ethofenprox. Spinosad is a naturalyte compound, produced by fermentation of a rare bacterium, Sacharopolyspora spinosa, a synthetic analogue compound have shown very good egg hatching inhibition activity followed by ethofenprox, fipronil and indoxacarb. At the lowest concentration (0.0012% a.i.), the egg mortality was higher than the other insecticides evaluated. The recommended concentration of spinosad (0.005% a.i.), indoxacarb (0.007% a.i.), fipronil (0.007% a.i.) and ethofenprox (0.02% a.i.) based on field application against three major predators namely E. amabilis, Pseudohypatopa pulverea (Lepidopteran) and Chrysopa spp. (Neuropteran) of lac insect exerted 100, 50.9, 61.5 and 84.6% egg hatching inhibition activity against eggs of E. amabilis under laboratory condition. Application of these insecticides will be very much effective in reducing the incidence of E. amabilis if applied at proper time. Our findings indicate that spinosad and fipronil with low active ingredients and high mortality could be the best option for suppressing the incidence of E. amabilis in the egg stage.