Abstract: Fifty strains of endophytic actinomycetes were screened in greenhouse pot experiments and leaf-disc test in lab. Two strains showed stable control effect on zucchini powdery mildew. In the leaf-disc test, the application of cell free filtrate of strains GKSHJA and PR1-8 showed 60.98% and 63.22% disease control efficiency, respectively. The control effect of strain GKSHJA with application 24 h before and after inoculation were 55.22% and 16.44%, respectively. The control effect of strain PR1-8 were 51.94% and 24.39% in the greenhouse potted seedlings inoculated with powdery mildew. The preinoculation application of cell free filtrate showed much higher disease control efficiency than postinoculation application. The applications of 5 times diluted cell free filtrates showed 27.81% (in GKSHJA treatment) and 30.19% (in PR1-8 treatment) less disease index than that in untreatment control. In field experiment, the control effect of biocontrol strains GKSHJA and PR1-8 were 56.33% and 69.88%, respectively, after application of 5 times dilution of cell free filtrate on naturally infected zucchini plants. These results showed that strains GKSHJA and PR1-8 were really potential biocontrol endophytic actinomycetes to control cucurbit powdery mildew and this research made a prior period research foundation for development and application of bio-pesticides on cucurbits powdery mildew.

Key words: Cucurbita pepo Linn, Sphaerotheca fuliginea, Endophytic antinomycetes, Control effect