You Are Here: Management Updates 2002 Archive October 11, 2002

Date: October 11, 2002
Category: Diseases
Subject: Take-All Patch, Gray Leaf Spot, Powdery Mildew, Rust, Red Thread, Fusarium Patch

We still are not having a lot of rain, but the weather is cooler and more humid. Fall diseases are returning. On bentgrass, take-all patch is active, especially in younger plantings.. This root disease responds very well to fungicides, especially azoxystrobin, but it must be watered-in while still wet on the leaves to delivery to the roots where the fungus is infecting the plant. Where soil pH is on the high side, applications of ammonium sulfate are useful and can be done now that the weather is cooler.

Gray leaf spot is still active and destructive in perennial ryegrass. So far, samples have only come from golf course fairways. Watch out for gray leaf spot in ryegrass athletic fields and lawns. It will remain active until after a hard frost. Fungicides are effective only in the early stages. The breeders are making good progress on getting improved GLS resistance in ryegrass cultivars.

In lawns and some other turf areas, powdery mildew and rust are common. Powdery mildew is white and looks like lime or flour on the leaf surface. It prefers cool, humid weather and poor air movement such as is found in shady areas. It responds to certain fungicides, but these are not recommended for this minor disease. Environmental management is very effective. Rust produces tiny pustules of orange powdery spores. The pustules are usually visible, or you can rub a white tissue on an infected leaf to see the orange spores. It is most common in slow growing turf due to drought, compaction, and/or low N. Growing turf is usually mowed off before the spores can form. The spores will die over the winter, and the turf will return to its healthy state in the spring. No treatment is usually necessary except to improve growing conditions. Red thread (and its pink puffs of spores when wet) is likely to occur in areas with similar conditions to those that favor rust.

Fusarium patch or pink snow mold has already started in northern New England and will be more widespread, mostly on golf course greens, with the coming cool, wet weather. Like hot weather Pythium blight, spots may look greasy. The spores of the fungus are easily spread by mowers etc. The disease is most common in wet areas, areas with shade or poor air movement, and where turf is lush from N fertilizers.

- Submitted by: Dr. Gail Schumann