Abstract: ObjectiveThe purpose of this study was to provide new approach for prevention and control of sugarcane smut and development of new biological pesticide by investigating the diversity of symbiotic bacteria isolated from Pseu-docnus echinatus and testing the bacteriostatic activities of their fermentations against Sporisorium scitamineum.MethodPure culture technology was used to isolate and purify the symbiotic bacteria from various parts of P.echinatus including its epidermis,intestine,stomach and intestinal contents.Diversity of symbiotic bacteria and its distribution characteristics in different tissues of P.echinatus were analyzed through 16S rDNA.Inhibition effects of the fermentations from symbio-tic bacteria against S.scitamineum were detected by Oxford cup method.ResultSeventy-nine symbiotic bacteria belon-ging to 46 species,35 genera,26 families,4 phyla were isolated from various parts of P.echinatus,and the dominant ge-nera were Bacillus(16.5%),Sphingopyxis(8.9%),Micromonospora(6.3%)and Citrobacter(6.3%).Taking"+"shaped, sporidum,"-"shaped sporidum and hypha of S.scitamineum as targets,19 live strains were screened using Oxford cup method.Among theses strains,the inhitition effects of Bacillus siamensis starin BGMRC03005 were the strongest against hypha(diameter of inhibition zone:25.40 mm),"+"shaped sporidum(diameter of inhibition zone:19.90 mm)and"-"shaped sporidum(diameter of inhibition zone:14.25 mm)of S.scitamineum.ConclusionThe species of cultivated bacte-ria in P.echinatus are diversified and most of them have strong antifungal activities against S.scitamineum.The selected B.siamensis strain BGMRC03005 has inhibition effects on the three forms of S.scitamineum,which could be developed into microbial pesticide.