Integrated Pest Management
Summer Patch in Turf
Annual bluegrass crown with dark colored, thick hyphae (as indicated by arrow) produced by the summer patch fungus, Magnaporthe graminicola.
Another view of dark hyphae, typically produced by the summer patch fungus.
Summer patch is a common disease in lawns of Utah. It is caused by a fungus called Magnaporthe poae.
SYMPTOMS
Summer patch is a warm weather disease. Symptoms are present during the months of May through September, and include dead circles and arches of turf that range in size from several inches to several feet in diameter. The summer patch fungus also produces microscopic, dark hyphae on the surface of the grass crowns and leaf sheaths.
CULTURAL CONTROLS
Cultural techniques that prevent the lawn from becoming stressed will help prevent this disease. In early spring or fall, the lawn should be aerated. Aeration improves water penetration and reduces thatch, thus alleviating conditions that cause stress. Nitrogen fertilizer should be applied frequently at low rates or in slow release forms such as sulfur coated urea or IBDU. This avoids undesirable flushes of growth which are more susceptible to disease. Mow the lawn at a height of 2-3 inches often enough so that only 30-40% of the leaf length is removed per mowing. In most soils, the lawn should be watered infrequently and deeply. Sandy soils will require more frequent, light irrigation. Wet the entire rot zone when irrigating.
CHEMICAL CONTROLS
Cultural techniques provide the most reliable control of summer patch, but in difficult situations fungicides may be necessary. It can be controlled with Tersan 1991, Fungo 50, Rubigan, and Cleary's 3336. The turf area to be treated should be irrigated the night before. The next day the fungicides should be applied and irrigated in before they dry on the foliage. These fungicides are best used as a preventative. Bayleton can also control summer patch, but it must be applied before the fungus becomes active in early summer.