You Are Here: Management Updates 1999 Archive June 25, 1999

Date: June 25, 1999
Category: Diseases
Subject: Drought, Anthracnose, Red Thread, Melting-Out

Drought continues to dominate the turf scene with many managers facing water deficits. The good news is that fungi are relatively inactive in such conditions. On golf courses, the most common problem appears to be anthracnose, a stress disease. Factors that enhance this disease are compaction, low mowing heights, low N, and insufficient water. The sticky spores are easily spread by mowers, feet, etc. The best fungicide treatment is a combination of chlorothalonil with a DMI (sterol-inhibitor) fungicide (e.g. Banner, Bayleton, Eagle) or with Heritage (some mixed reports). If anthracnose has developed into the crown rot (basal rot) stage, don't expect fungicides to save infected plants, but they may protect those whose crowns are not yet infected. To diagnose crown rot, try to pull individual plants out from the turf and look for the charcoal black evidence of the anthracnose fungus at the base of the plant. Anthracnose often appears first in annual bluegrass but can also affect bentgrass.

Red thread continues to plague many lawns. Another problem that may appear in lawns is melting-out. Melting-out is usually described in textbooks as a disease that develops from heavy leaf spot infections in the spring in prolonged wet weather where lawns have received excessive N fertilizer. Melting-out can also develop during stressful periods when some leaf spot is present, such as areas where a lawn is not sufficiently irrigated. Essentially, the leaf spot fungus overtakes the plant when it is stressed. You may be able to see the reddish-brown lesions of the leaf spot fungus along the length of the leaf blade and sometimes extending into the crown of the plant. If the crown remains white and the stress can be diminished, the plants should recover. Avoid N applications during this hot, dry weather. Fungicides should not be necessary and probably won't be very effective. Overseed thinned areas later in the season. Keep in mind that the most common cause of the straw color of lawns at this time is drought dormancy

- Submitted by: Dr. Gail Schumann