Studies on efficacy of green insecticides on mulberry silkworm, Bombyx mori L. through rearing performance

The bioassay study was conducted in the Department of Sericulture, UAS, GKVK, Bengaluru during 2018, to test the efficacy of different insecticides on mulberry leaf roller Diaphania pulverulentalis (Hampson). The effective insecticides with optimum dose were sprayed on mulberry plants and fed to silkworm Bombyx mori L at 10, 15, 20, 25 and 30 days after spraying (DAS) to find the waiting period of such chemicals on silkworms. The results revealed that among the eight insecticides tested, lambda- cyhalothrin and emamectin benzoate were highly toxic to silkworms with 100 per cent mortality even after 30 DAS. However, the insecticide Chlorofenapyr (1.5 ml/liter) recorded less mortality (12.09%) of silkworms at 10 days after spray. Similarly, Azadirachtin and Novaluron (10.00% & 9.67%, respectively) at 25 DAS. Whereas, the insecticides Profenofos and fipronil at 30 DAS recorded less mortality rate of 11.00 per cent and 10.67 per cent respectively, which were on par with that of standard check and untreated control. Similar trends were observed with respect to moulting duration (h), instar duration (h) and cocoon yield (g/100cocoon) of silkworms. The findings of present study clearly indicated that the insecticide Chlorofenapyr was proved to be less toxic to silkworms even at 10 DAS followed by Azadirachtin and Novaluron at 25 days after spraying and Profenofos and fipronil at 30 days after spraying. However, lambda- cyhalothrin and emamectin benzoate were highly toxic to silkworms even after 30 DAS. Chlorofenapyr, Azadirachtin and Novaluron could be the alternate insecticides to be thought to manage the mulberry leaf roller in view of the ban on Dichlorvos the safest insecticide recommended in mulberry.