Hot and humid weather is here, and many areas of the central U.S. have seen plenty of rainfall lately. All of that together can be stressful for cool-season turf, especially on putting greens. As I have been conducting Course Consulting Service visits, I’ve encountered a lot of wet wilt over the past couple of weeks.
Wet wilt is very different from dry wilt. Wet wilt occurs when the soil is saturated and the weather is hot and humid, especially in the overnight hours. Under these conditions, the turf is not able to adequately transpire because transpiration pull is interrupted by high relative humidity around the leaves. The stomates in the leaves are not able to evaporate enough water to draw additional water from the roots to adequately cool the plant and help it recover from heat stress. This causes the plant to “cook” and wet wilt. Putting green turf affected by wet wilt dies back and has a brown and matted appearance.
Ensuring adequate drainage and air movement is critical to avoiding wet wilt. Efforts to improve subsurface drainage through cultural practices or by installing drainage infrastructure helps avoid soil saturation. Any efforts to improve air movement are also beneficial. Additional air movement can increase the amount of transpiration in the plant, allowing it to cool and recover. Methods to improve air movement include tree and shrub removal around putting greens – especially those blocking prevailing winds – or installing fans. Fans can be helpful in many situations where air movement is minimal, and if your course doesn’t currently have fans installed there are portable options. Ideally, fans should be located to blow with the prevailing wind and not against it.
If your putting greens have wet wilt, raising the height of cut, minimizing mechanical wear by installing smooth rollers, reducing mowing and rolling frequency, and postponing any topdressing or vertical mowing is recommended to help the turf recover. In areas of significant thinning, you can limit the development of algae by applying fungicides like chlorothalonil or mancozeb until topdressing can be done after peak wet wilt stress. If you have any additional questions about how to manage your putting greens during the intense summer heat and humidity, please reach out to your regional USGA agronomist.
Central Region Agronomists:
Zach Nicoludis, regional director, Central Region – znicoludis@usga.org
Tom Gould, agronomist – tgould@usga.org
Information on the USGA’s Course Consulting Service
Contact the Green Section Staff