INTRODUCTION AND ESTABLISHMENT OF STRAINS OF ENTEROBACTER-CLOACAE IN GOLF COURSE TURF FOR THE BIOLOGICAL-CONTROL OF DOLLAR SPOT

Topdressings prepared from cornmeal-sand mixtures infested with strains of Enterobacter cloacae were used to introduce bacterial antagonists into bentgrass putting greens naturally infested with Sclerotinia homoeocarpa. Topdressings fortified with E. cloacae strains EcCT-501 and E1 significantly reduced dollar spot disease development when compared with untreated plots. In some experiments, monthly applications of strain EcCT-501 provided up to 63% disease control and was as effective as iprodione or propiconazole in reducing dollar spot severity. Disease suppression induced by strains EcCT-501 and E1 was evident up to 2 mo after application. Dollar spot suppression was more effective when E. cloacae was applied as a preventive treatment rather than a curative treatment. However, strain EcCT-501 significantly reduced dollar spot severity when applied to severely diseased turf. Introduced populations of selected strains of E. cloacae in putting greens were monitored in both 1988 and 1989. Recoverable populations of selected E. cloacae strains immediately after application were approximately 10(7)-10(9) colony-forming units (cfu) per gram dry weight of thatch in both 1988 and 1989. Although populations in both years declined, they remained at levels greater than 10(4) cells per gram for up to 13 wk and were detectable in the spring of 1989 after 1988 summer applications.