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Management of Dollar Spot on Creeping Bentgrass with Metabolites of Pseudomonas aureofaciens (TX-1)

Antifungal extracts from four strains of bacteria that were selected for their ability to inhibit fungal turfgrass pathogens were compared for in vitro activity. The cell extract from Pseudomonas aureofaciens Tx-1 (ATCC 55670) exhibited the greatest antifungal activity against selected turfgrass pathogens. Purification of the extract yielded a single active component that was identified as phenazine-1 carboxylic acid (PCA). Minimum inhibitory concentrations of PCA to tested fungal pathogens ranged from 10 to 25 µg/ml. In greenhouse studies, PCA provided management of dollar spot on creeping bentgrass equal to that of the commercial fungicides triadimefon and chlorothalonil at equivalent rates of active ingredient. Phytotoxic effects were observed on creeping bentgrass in greenhouse but not field evaluations of PCA at the rate of 0.48 g/m². At the end of 2 years of field study, PCA applied every 14 days at 0.15 g/m² provided dollar spot management on creeping bentgrass equal to that of chlorothalonil applied every 10 days at the label rate of 0.48 g/m².