Studies with Tn5 mutants of Pf-5 which differ in antibiotic production, indicate that D. poae and S. homoeocarpa are sensitive also to pyrrolnitrin and possibly another antibiotic. Stenotrophomonas maltophilia C3, which was isolated in Nebraska from turfgrass, was originally found to be inhibitory to Rhizoctonia solani . C3 has been NC-125 pg 1 found to inhibit spore germination and growth of a wide range fungal pathogens, including Bipolaris sorokiniana, Botrytis cinerea, Pythium ultimum, and Sclerotinia sclerotiorum. When applied to bean blossoms, strain C3 suppressed blossom colonization of B. cinerea and S. sclerotiorum. Foliar and seed applications of C3 have been effective for controlling several pathogens.
Antagonistic activity appears to be associated with the chitinase.
Several isolates of Bacillus sp. and a Pseudomonas sp. have been found in Indiana to suppress Mn oxidation, and thereby suppress pathogenesis by the take-all pathogen of wheat, Gaeumannomyces graminis var graminis. These Indiana bacteria do not inhibit growth of the take-all pathogen. Antibiosis, competition, and possibly predation are all implicated in with these bacterial biocontrol agents. Fungal antagonists also have been widely investigated for their efficacy against plant pathogens. Sporidesmium sclerotivorum, the nearly obligate parasite of the sclerotia of Sclerotinia sp., was developed by the USDA group in Beltsville and is being applied in Iowa as a biocontrol agent of white mold of soybeans, incited by S. sclerotiorum.