You Are Here: Management Updates 1998 Archive June 4, 1998

Date: June 4, 1998
Category: Diseases
Subject: Weather, Yellow Patch

This is a somewhat confusing time for turf diseases because of the variable temperatures- relatively warm in the daytime but still quite cool at night. Despite the lack of rain last week, the cool nights bring on considerable moisture in the form of dew and the turf can remain wet for many hours during these lower temperatures. The coming week is predicted to be quite cool both in the day and at night which will reduce stress, but rainfall has been plentiful which is always conducive to fungal diseases. Watch fertility levels to avoid nitrogen deficiency, but apply only small doses of nitrogen in wet conditions to avoid high nitrogen diseases.

Yellow patch (cool season brown patch) is active on both annual bluegrass and bentgrass of golf courses. The symptoms are appearing as yellow rings with green centers. The good news is that the fungus is strictly on the leaves and is, therefore, easy to treat with fungicides. However, many fungicides that are effective for summer brown patch do not work effectively against yellow patch which is caused by Rhizoctonia cerealis. ProStar, Heritage, and Banner Maxx are all labelled for yellow patch. It is not a very damaging disease, so you may just want to let the warm weather take care of the problem and not apply a fungicide for this problem alone. Other factors that increase this disease are high nitrogen fertility and long periods of moisture. Mowing or whipping the dew off in the early morning should help. The same disease can develop in lawns but no fungicide is recommended because the disease causes so little injury.

We had many rainy days in early May followed quickly by an extended dry period. Some lawn areas went into drought dormancy. These areas are generally in the full sun and have a wide, irregular appearance (i.e. no circular patches of fungal diseases). The recent rains and cooler weather should result in fairly rapid recovery. Lawns damaged by grub feeding will peel back because the roots have been destroyed. Droughty lawns should have good root structure. If you peel back the straw-colored leaves, individual plants that are green and white in the center and crown of the plant should recover soon.

- Submitted by: Dr. Gail Schumann