Record of Natural Incidence of Entomopathogens in Gangetic Alluvial Zone of West Bengal

A survey was conducted to find out the natural incidence of entomopathogens and their pathogenicity in Gangetic alluvial zone. Three major groups of entomopathogens such as fungus, bacteria and virus have been observed and isolated from natural infected insects. Natural occurrence of viral and fungal diseases was much more pronounced, so far as field infestation and laboratory cultures were concerned. Pathogenicity of the viral isolates (V1, V2 and V3) caused 83.33, 91.67 and 56.67 per cent mortality for S. litura, H. armigera and S. obliqua, respectively. Characterizations of pathogenic microbes isolated during the course of investigation were also attempted. It revealed that the entire three isolated viruses belonged to polyhedrosis type. White mascardine fungus named, Beauveria bassiana isolated from infected Spilarctia obliqua</> and Amritodus atkinsoni</> resulted 33.67 and 76.67 per cent mortality, respectively. Three different types of bacterial colonies were isolated from disease infected larvae of Earias vitella. Pathogenicity test of these isolates revealed only one isolate having 53.33 per cent mortality. But, in case of Pieris brassicae among two isolates, only one caused 26.67 per cent mortality. The isolates for both the insects those caused more or less pathogenicity after isolation belonged to single genus Bacillus.