Managing Turf Diseases Before and After Severe Weather

By Lane Tredway, technical services manager for Syngenta

Extreme weather conditions, whether too hot, too cold, too dry, or too wet, can impose a great deal of stress on turf grasses. This is particularly the case for golf course turf, where the management is intense and there is little tolerance for reductions in turf quality. Weather extremes seem to be becoming the norm, so it pays to have a plan for how to deal with them. Extremely wet weather and flooding are particularly difficult to manage because of the multiple stresses involved. Saturated soils often lack the oxygen that roots need to grow and survive. Flooding brings silt deposition that can damage turf in the short- and long-term. Cloudy conditions deprive turf of sunlight and the energy that it needs to recover. In addition, excess moisture creates an ideal environment for many turf diseases that prey on these weakened turf plants.

Algae and Pythium diseases are often the first pathogens to attack during and after periods of wet weather, so keeping these in check should be top priority. Algae is often thought of as a secondary problem, but can actively damage turf by clogging soil pores and producing herbicide-like toxins in the turf canopy. For algae control, Daconil® brand fungicide products, mancozeb, and copper hydroxide are the most effective options. Phosphonate products such as Appear® II fungicide also have preventive activity against algae, and are often tank-mixed with a Daconil brand. Under normal conditions, applications on a 14-day interval are sufficient to prevent algae. During and after extremely wet weather, intervals may need to be shortened to seven days to provide acceptable control.

Depending on the grass species and climate, Pythium blight, Pythium root rot, or both may be primary concerns during periods of wet weather. Accurate diagnosis is crucial to selecting the best product and application method. For Pythium blight, applications should be allowed to dry to protect the foliage. For Pythium root rot, fungicides must be moved into the soil with irrigation or rainfall for best results.

Syngenta offers Subdue Maxx® fungicide, which has broad spectrum activity against foliar and root rotting Pythiums. Heritage® Action™ fungicide is also an effective option for certain Pythium species, in addition to many other turf diseases. Both products are also available in granular formulations, Subdue® GR and Heritage G fungicides, which are ideal for times when the soil may be too wet for the sprayer.

Finally, keep in mind that fungicide application intervals may need to be reduced overall during and after periods of wet weather. Being on the outside of the plant, contact fungicides are not likely to persist for 14 days under frequent rainfall. As for systemic fungicides, although most do not leach through the soil profile very readily, they may be broken down more quickly in saturated soils due to hydrolysis or microbial activity. Consider repeat applications of contact and systemic fungicides when wet weather subsides to boost prevention of key diseases.

Syngenta offers many products that can assist in the preparation for and recovery from weather extremes. For more details, visit ©2019 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties. Please check with your local extension service to ensure registration status. Action™, Appear®, Daconil®, Heritage®, Subdue®, Subdue Maxx® and the Syngenta logo are trademarks of a Syngenta Group Company.

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