EVALUATION OF BACTERIAL ANTAGONISTS FOR REDUCTION OF SUMMER PATCH SYMPTOMS IN KENTUCKY BLUEGRASS

Ten bacterial strains previously identified for their ability to contr ol soilborne pathogens on agronomic crops were evaluated for their abi lity to suppress summer patch disease caused by Magnaporthe poae in Ke ntucky bluegrass (Pen pratensis L). Bacterial strains varied in the ab ility to inhibit the growth of M. poae in agar plate bioassays, althou gh most strains inhibited the fungus to some degree. Three strains ori ginally isolated from wheat, Pseudomonas fluorescens 2-79, P. fluoresc ens 13-79, and Bacillus subtilis D-39Sr, and two strains originally is olated from cotton, Enterobacter cloacae EcH-1 and EcCT-501, significa ntly reduced summer patch symptoms by between 29 and 46% compared to u ntreated control plants after a S-week period in the growth chamber. T he live strains did not reduce summer patch disease in field trials in 1990. However, in 1991, B. subtilis D-39Sr and E. cloacae EcH-1 reduc ed summer patch severity by 53 and 49%, respectively, over the entire season compared to untreated control plots. In 1994, both B. subtilis D-39Sr and E. cloacae EcH-1 also reduced summer patch severity over th e entire season by up to 39 and 34%, respectively, compared to the unt reated control in field plots, All five bacteria that reduced summer p atch in growth chamber studies were present in the rhizosphere of gree nhouse/growth chamber grown turfgrass at 10(4) to 10(6) CFU/g of fresh weight sample 2 weeks after application to plants. A single sampling of field plots during 1991 and four separate samplings of field plots during 1994 indicated that introduced bacteria were present within the turf at populations above 10(3) CFU/g of sample.