You Are Here: Management Updates 1998 Archive June 10, 1998

Date: June 10, 1998
Category: Diseases
Subject: Leaf Spot/Melting-Out, Anthracnose

Lawns: Lots of melting-out from leaf spot that got out of control. Several factors contributed to this: extended wet weather in early May which caused delays in mowing; mowing was then done on very long leaf blades which stressed the plants; a droughty stress period followed. Usually you can find leaf spots on newly infected leaves, but the crowns of the plants get infected and then the entire plant collapses ("melting-out"). Fungicides don't usually help much. Overseeding affected areas is most cost-effective.

Golf courses: Anthracnose crown rot is occurring, mostly on annual bluegrass. The black hair-like setae of the fungus can often not be seen on the leaves in cool weather, but if you pull up a plant and look at the base, the charcoal black fungal structures may be visible. Even with fungicide treatment, these plants may not recover. The best fungicide effects come from combinations of chlorothalonil plus a systemic. Factors that make the disease more severe are: low mowing heights, compaction, poor drainage, low nitrogren. The fungus produces abundant spores which are easily spread by mowers. Hose off mowers or change mowing order when moving from affected areas to other areas.

- Submitted by: Dr. Gail Schumann