Abstract

Silkworm, being a poikilothermic, is susceptible to various infectious diseases caused by various pathogenic microorganisms. Among diseases, mixed infection is caused by many combinations virus and bacteria, bacteria and bacteria and bacteria and virus which cause havoc in silkworm rearing. The larvae showing symptoms of mixed infection reported a new bacteria Alcaligenes faecalis which was isolated and confirmed through 16S rRNA gene action. During investigation, when A. faecalis was administered to third instar larvae of PM × CSR2, pathogenic effect was noticed and resulted in variation in rearing and cocoon parameters. The larval weight ranged from 0.78 (T6)-0.85 (T5), 2.47 (T6)-3.52 (T3) and 18.70 (T6)-22.00 (T3) g/10 silkworms during end of the third, fourth and fifth instars of third instar inoculated batch, respectively. In addition, the per cent larval weight reduction also noticed the same trend. Further, the extended maximum and minimum larval (24.65 and 21.25 days) and moulting duration (79.26 and 63.28 h) were noticed in T5-Alcaligenes faecalis+Bacillus subtilis+Lysinibacillus sphaericus and T1-Alcaligenes faecalis infections. It is inferred that, sole administration of A. faecalis was found less pathogenic compared to combination. In addition to this, maximum larval mortality (71.80%), less number of days for ET50 for symptom expression (6.88 days) and mortality (8.50 days), less ERR (28.20%) resulted in T6-Alcaligenes faecalis+Bacillus subtilis+NPV and minimum mortality (53.75%), maximum ET50 for symptom expression and mortality (20.78 and 23.14 days), ERR of 46.25 per cent was observed when silkworms were inoculated with A. faecalis alone.