You Are Here: Management Updates 2002 Archive July 2, 2002

Date: July 2, 2002
Category: Diseases
Subject: Pythium, Brown Patch, Anthracnose, Summer Patch, Gray Leaf Spot, Red Thread

We don't often have classic Pythium weather in New England, but this is it. Watch for: white, cottony mycelium, small tan to bronze spots on close-cut turf or greasy leaf blades, especially in higher cut turf. Brown patch will be even more widespread. It generally makes larger patches with grayish "smoke rings" of mycelium and recently infected turf leaf blades. However, in very hot, humid weather, the fast growing mycelium of Rhizoctonia can look white- either at the edge of a patch in close-cut turf or as a mass of weblike mycelium in higher cut turf. How to determine which it is? Look closely at the leaf blades. Pythium generally destroys the entire leaf, but Rhizoctonia causes irregular, tan to bruised looking individual lesions on the leaf blade.

Cultural practices for both: 1) hold off any fertilization until the hot weather passes, 2) try to wait until turf is dry before mowing- or avoid areas with "hot spots" of Pythium activity (usually where turf stays wetter), 3) avoid night watering until hot weather passes. My weather report says 57 on Thursday night which is enough to stop both diseases as well as a fungicide.

In general, other turf stress diseases will be enhanced by this weather- especially anthracnose and summer patch. Judicious syringing to cool plants in the heat of the day will help them survive. Keep in mind that the DMI fungicides (e.g. Banner, Bayleton, and Eagle) have some growth regulator activity which can be enhanced in hot weather. We don't know exactly what triggers the start of gray leaf spot in perennial ryegrass, so watch that carefully for any unusual activity. Try to get a lab confirmation if you suspect gray leaf spot. So far, it has been a problem mostly on golf course fairways, but it is possible that lawns and athletic fields could be affected. Lawn areas with red thread will probably look worse until the weather cools off. The humidity and late day thunderstorms encourage fungal growth, and the heat inhibits turf recovery.

- Submitted by: Dr. Gail Schumann