Phenology of Eri silkworm Samia ricini (Donovan) in Lower Assam and its impact on upscaling eri seed production

Abstract

Aim: A phenology study on the seed cocoon rearing performance of Samia ricini (Donovan) in different seasons of Lower Assam and subsequent production of disease-free laying was undertaken. Methodology: In each season, four batches of seed cocoon rearing were conducted on eri silkworms of Borduar race (n=100 dfls) which were reared only on the castor, the primary host plant, to eliminate the variability due to different host plants. The data on different seed cocoon rearing and reproductive parameters were recorded for every rearing and pooled season-wise for comparison. Results: The highest seed cocoon yield per dfl was recorded during autumn (215.92±6.24 nos) followed by winter/spring and late monsoon seasons. During autumn, significantly higher ERR% (90.69±1.01) was observed. Grainage operations conducted on the seed cocoons of various seasons revealed ideal dfl to cocoon ratio during autumn (1:3.5) and late monsoon (1:4.2). The percentage of moth emergence was significantly high in autumn (92.27± 2.90), followed by late monsoon (89.07± 5.38). Interpretation: Results evidently indicated that late monsoon and autumn seasons spanning from September to November months can be utilized effectively for large scale eri silkworm seed production in Assam. Key words: Eri silkworm, Phenology, Reproductive performance, Samia ricini, Seed cocoon rearing