Elisabeth Clover Artemis Kitchin
Abstract
North Carolina is within the transition zone which allows for cultivation of both warm- and cool-season turfgrasses. Diseases are problematic in this region, especially on cool-season turfgrasses. In particular, dollar spot and Pythium root rot can be devastating if not managed properly. Preventive fungicide applications provide the best suppression of these diseases, yet curative applications may be necessary if preventive timings are missed. Turfgrass managers expect rapid response from curative fungicide applications, but the response time likely varies among fungicides, the diseases targeted, and the environment at the time of curative application. A two-year study examining single curative applications of fungicides for dollar spot was conducted. Curative applications of fungicides were evaluated in 2019 for control of Pythium root rot. Both studies were conducted at the Lake Wheeler Turfgrass Field Laboratory in Raleigh, NC. Both diseases were allowed to develop to roughly 30% disease prior to fungicide application. Disease severity was rated at least twice a week using a point intersect method to quantify the area affected with disease. In both years of the dollar spot study, disease severity was reduced below 5% 10 to 18 days after the initial application for the systemic fungicides (mefentrifluconazole, iprodione, and pydiflumetofen). Fluazinam and chlorothalonil did suppress dollar spot in the study, but not as well as the systemic fungicides. In the Pythium Root Rot trial, treatments could not decrease disease below 15%. If curative fungicide applications for dollar spot are needed, products should have systemic activity and will likely take 7 to 14 days to facilitate recovery. Curative applications for a root disease may not provide acceptable control, thus preventive applications are suggested. In both cases, disease suppression was not immediate and may also not be complete demonstrating why preventive applications are critical.
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