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

Date: November 25, 2002
Category: Diseases
Subject: Yellow Patch, Fusarium Patch, Bentgrass Cold Injury

As the cool, wet weather continues for most locations, conditions remain conducive for two common diseases:

Yellow patch (cool season brown patch) usually causes fairly large patches of affected grass (similar to brown patch in the summer). It is caused by a different fungal species than summer brown patch, Rhizoctonia cerealis , so only a few fungicides are effective (see fungicide chart). The symptoms are quite variable depending on temperature, moisture, and foliar N levels. Sometimes you can actually see webby mycelium on the turf; other times you may only see a slight tip blight- brownish or purplish. The disease is not usually severe enough to kill turf. If foliar growth has ceased, symptoms will not disappear until spring even with fungicide treatment. The disease can occur on almost any turf- golf courses and lawns.

Fusarium patch (or pink snow mold) is also likely to be seen on golf courses at this time. It will probably appear as small (1-3") greasy or coppery spots. As with yellow patch, the disease is more severe at high foliar N. The fungus (Microdochium nivale) produces abundant spores that are easily tracked or washed to new areas. Treat the disease as you would hot weather Pythium blight. Divert traffic from affected areas. Try to mow when dry if you are still mowing. Spot treat with fungicides where necessary.

Bentgrass cold injury shows as fairly evenly distributed purplish tips (not in patches usually). This is not a leaf spot problem and will correct itself with new growth. Snow mold winter protection fungicide applications can be applied at any time, but will be most effective if foliar growth has ceased.

- Submitted by: Dr. Gail Schumann