Abstract:

【Objective】To understand and define the pathogen origin and spreading track of white muscardine caused by entomopathogenic fungus Beauveria bassiana in southwestern Anhui and to control prevalence of silk disease.【Method】Seventy isolates of B. bassiana from silkworm cadavers, rearing room and soil from surrounding mulberry garden, cropland, and adjacent pine plantations were tested for clustering and 3-d principal coordinate analyses with the ISSR data.【Result】The local B. bassiana population is heterogenous, with obvious dominance. Among the 6 groups, only group II-1 (the primary disease origin) and group IV (the secondary origin) caused enzootic muscardine, while both of them were neither related to the isolate used as fungal insecticide applied against the masson pine caterpillar nor to the indigenous isolates prevailing in pine caterpillar population. A bioassay revealed that LC25, LD25 and LT25 caused by the strain isolated from infected pine caterpillars were 1 327, 1 378, and 1.5 times of LC75, LD75 and LT75 caused by a typical pathogenic strain isolated from silkworm, respectively. 【Conclusion】 Based on obvious host specificity of the isolates from the pine caterpillars, the use of B. bassiana insecticide developed from these isolates against the pine caterpillars is comparatively safe to sericulture. The epizootic caused by B. bassiana in surrounding mantid populations is not associated to the white muscardine of silkworms.

Key words: silkworm, Beauveria bassiana, white muscardine, enzootic, masson pine caterpillar