You Are Here: Management Updates 2002 Archive June 25, 2002

Date: June 25, 2002
Category: Diseases
Subject: Pythium, Fusarium Blight, Brown Patch, Anthracnose, Summer Patch

In most areas of New England, there will be hot, humid weather for the next couple of days followed by a moderate weekend. Here are some hot weather tips for turfgrass diseases for the coming weeks:

Pythium blight is not as common as people think in New England. It really has to be hot and humid for this disease to cause significant problems. It is most severe where turf is lush from recent fertilizations. Ryegrass lawns are more susceptible than Kentucky bluegrass ones. Temperatures need to be 86F (maximum) and no lower than 68 F at night with at least 14 hours of relative humidity 90%. That means really uncomfortable sleeping weather. If the weather is going to cool off soon, Pythium blight is unlikely to be significant. In some cases, you may see the start of the disease as small greasy or reddish spots in the turf. Spot treatments of disease-prone areas with fungicide may be sufficient.

Fusarium blight is not common, but does occur on higher cut turf and can be confused with Pythium blight. Like Pythium blight, it is a foliar disease that is more severe with high N and very warm and wet conditions. It too can cause greasy looking leaf blades, but it will not produce the cottony white mycelium of Pythium. It is a foliar stress disease that usually disappears when the weather cools off. Most contact fungicides are effective.

Brown patch can occur whenever night temperatures remain above 59 F and conditions are humid and rainy. Like Pythium blight it is more severe on ryegrass lawns, and disease is more severe at high N. But one cool night in the lower 50s is the same as free fungicide. The disease will be effectively stopped.

Anthracnose is a stress disease, so hot weather can exacerbate existing problems and kill off plants already infected by the basal rot stage of the disease. The best defense is to relieve as many other stresses as possible during hot weather to help plants survive.

Summer patch most commonly occurs when rain is followed by hot temperatures. This root disease of Poa annua and Kentucky bluegrass can only be treated by fungicides if they are watered-in to reach the roots.

- Submitted by: Dr. Gail Schumann