Objective  To investigate the diversity of Isaria from different soils in some areas of China, and to determine their bioactivity against Phyllotreta striolata, so as to promote the application of Isaria as biocontrol agents.

Method  Soil samples were collected from different habitats in Fujian, Guangdong, Yunnan, Guizhou, Hunan, Hubei, Henan, Hebei and Guangxi Provinces (Regions). Isaria strains were isolated and purified by selective medium, and identified based on morphology and molecular markers. The Shannon-Weiner and dominance indexes were used to evaluate the biodiversity. The biological activities of Isaria strains against P. striolata were determined by immersion method.

Result  A tatol of 41 Isaria strains were isolated from more than 200 soil samples. The dominant species was I. javanica with 34 strains and a dominance index of 0.829. Meanwhile, five strains of I. fumosorosea, one strain of I. farinosa and one strain of I. cateniannulate were isolated. The woodland habitat had the highest biodiversity for Isaria with Shannon-Wiener index of 1.121, followed by fallow land, orchard, farmland, grassland with the Shannon-Wiener indexes ranged from 0 to 0.349. Woodland habitat had the most uniform distribution among species, with the dominance index of 0.468, and the dominance indexes of fallow land, orchard, farmland and grassland ranged from 0 to 0.159. The results of bioassay showed that most tested strains had certain activity against P. striolata. The strain IfH6102 had the highest activity with the corrected mortality of 60.89% at 11 days after treatment.

Conclusion  Isaria is widely distributed in the soil of China. The woodland has the highest biodiversity for Isaria, and Isaria has the potential to be used for controlling P. striolata.