Pythium root rot (PRR) is a disease that can rapidly devastate large swaths of golf course putting greens, with little recourse once symptoms appear. Golf courses routinely apply preventative fungicides for root diseases, which may be altering the rhizosphere microbiome leading to unintended impacts to plant health. A multi-year field trial was initiated on a ‘T-1’ creeping bentgrass (Agrostis stolonifera L. cv. ‘T-1’) putting green in College Park, Maryland to evaluate preventative PRR management for disease suppression and impacts to rhizosphere bacterial communities. Fungicides commonly used to prevent PRR and a biological fungicide were repeatedly applied to experimental plots throughout the growing season. Rhizosphere samples were collected twice annually from each plot to evaluate rhizosphere bacterial communities through amplicon sequencing and monitor biological control organism populations via qPCR. Cyazofamid was the only treatment to suppress PRR in both years compared to the control. Fosetyl-Al on a 14 d interval and Bacillus subtilis QST713 also reduced PRR severity in 2019 compared to the non-treated control. Treatments did not significantly alter bacterial communities, however seasonal environmental changes did. Repeated rhizosphere targeted applications of B. subtilis QST713 appear to have established the bacterium into the rhizosphere, as populations increased between samples, even after applications stopped. These findings suggest that QST713 may reduce pathogen pressure when repeatedly applied and can reduce fungicide usage during periods of low PRR pressure.
Cross-Polarized Magic-Angle Spinning (sup13)C Nuclear Magnetic Resonance Spectroscopic Characterization of Soil Organic Matter Relative to Culturable Bacterial Species Composition and Sustained Biological Control of Pythium Root Rot.