Abstract
Eri silkworm Samia ricini (Donovan) is a polyphagous insect and the farmers of North East India rear the silkworm mainly on two primary host plants viz., Castor Ricinus communis L., and Kesseru Heteropanax fragrans Seem., for production of cocoons and pupae. The micro-climate around Kesseru leaves, topography of the leaf surface and the typical leaf exudates influence the growth and development of varieties of leaf surface microorganisms. The phylloplane mycoflora play important role in supplying different types of nutrients to the plants as well as to the silkworm. During the study on the phylloplane mycoflora of Kesseru on three different types of leaves viz., tender, semi mature and mature, nine fungi were recorded, isolated and identified during autumn while seven fungi were isolated and identified during winter season. Aspergillus fumigatus was the dominant and Alternaria alternata was the co-dominant species found in both the seasons while Mucor sp., Curularia sp., Fusarium sp., Helminthosporium sp., Candidus sp., Penicillium sp. and Cercosporella sp., showed less percentage of occurrence. Evaluation on the rearing performance of Eri silkworm during the corresponding seasons revealed 84.50% hatching, 74.87% ERR and 14.56% SR in autumn as compared to 82.50%, 76.82% and 13.99% respectively in winter season. Assessment on cocoon and yarn quality revealed higher shell weight (0.38 gm), lesser degumming loss (8.00%), higher yarn count (8.25 nm) with higher yarn recovery (80.00%) during autumn, while during winter shell weight, degumming loss, yarn count and yarn recovery were recorded as 0.36 gm., 8.00%, 20 nm and 78.00% respectively. The occurrence of fungal species was more dominate in the autumn season with comparatively better rearing performance and economic traits during the period as compared to winter season.
