Impact of Treated Castor Leaves on Growth and Productivity of Eri Silkworms: A Bioassay Study

Abstract

One of the most common foliar diseases in castor cultivation for ericulture is Cercospora leaf spot, caused by Cercospora ricinella Sacc. & Berl. which seriously damages leaves meant as food for eri silkworms. Deterioration in the quality or quantity of castor leaves primarily hampers the health of eri silkworm, which ultimately affects the economic parameters of the cocoons produced by them. A bioassay study was conducted during 2019-2021 at College of Sericulture, Assam Agricultural University, Jorhat, Assam, to check the effects of feeding castor leaves, treated with treatments found promising for eco-friendly management of Cercospora leaf spot of castor. Eight treatments with three replications were taken for the experiment which included a phytoextract of Tulsi (Ocimum sanctum) @ 5%, a bio agent (Trichoderma viride) @ 5% and a fungicide (Copper oxychloride) @ 0.2 % and their combinations, applied as foliar spray at 15 days interval after 30 days of transplanting. These treated leaves were fed as first feed to the 3rd instar silkworms after maintaining 25-30 days as safe period. Silkworms fed with castor leaves treated with T.viride + Tulsi extract showed the best results in overall health (ERR 91.66%, Fecundity 391, Shell ratio 13.44%) followed by worms fed with leaves treated with Tulsi extract + T. viride + COC (ERR 80.55%, Fecundity 370, Shell ratio 12.59%).