In vitro and in vivo antagonism of Streptomyces violaceusniger YCED9 against fungal pathogens of turfgrass

The biocontrol agent Streptomyces violaceusniger YCED9 inhibited in vitro growth of seven fungal pathogens of turfgrass. Three different antibiotics were produced by the actinomycete, including nigericin, geldanamycin and a complex of macrocyclic lactone antibiotics. Each had a different spectrum of antifungal activity. Only nigericin was detected in soil or in grass rhizospheres inoculated with YCED9. However, all three antibiotics were produced when YCED9 was grown in a mixture of moistened grass and thatch. In greenhouse experiments, a grass seedling disease caused by the Rhizoctonia solani and a crown-foliar disease caused by Sclerotinia homeocarpa were partially controlled with commercial spore formulations of YCED9.