LEAF SPOT

leaf spot/melting out in bermudagrass	Characteristic	Description
	Host Grass Species	bluegrasses, bermudagrass
	Month(s) with symptoms	March to June, Sept to November
	Stand Symptoms	irregular distribution across turf stand
	Foliar Symptoms - Location/Shape	oval leaf spots
	Foliar Symptoms - Color	yellow, tan, brown
	Root/Crown Symptoms	none
	Fungal Signs	none

 

Note: Still not sure if this is the right disease? The Turfgrass Disease Identification program may be helpful. Or consult the experts at the Turf Diagnostics Lab. Check the TurfFiles glossary for definitions of unfamiliar terms.

FACTORS AFFECTING DISEASE DEVELOPMENT

Leaf spot/melting out is one of several Helminthosporium diseases which survive in thatch during periods that are unfavorable for disease development. These fungi are most active during periods of cool (60 to 65°F) and wet weather, but some are able to cause disease whenever temperatures are above freezing.

Leaf spot/melting out is most severe on turf that is growing slowly due to adverse weather conditions or improper management practices. Shaded areas with little or no air movement result in weak turf and extended periods of leaf wetness that favor disease development. Deficient or excessive nitrogen, excessive thatch, extended periods of leaf wetness, drought stress, and low mowing heights are factors that encourage the development of Helminthosporium diseases. These fungi may spread to the crowns and roots and cause melting out, which is most severe during periods of hot weather.

Certain cultivars of turfgrasses are very susceptible to injury from Helminthosporium diseases while many of the newly released cultivars have exhibited good resistance.

CULTURAL CONTROL

Use turfgrass cultivars with resistance to this disease when available. Planting resistant cultivars is one of the most effective and economical ways to manage leaf spot and melting out. Select cultivars based on regional trials and University recommendations. If planting cool-season turf, use blends and mixtures of multiple species and/or varieties when possible.

Fertilize to meet the nutritional needs of the turf but avoid over-stimulation and the development of lush, succulent growth. Do not apply more than one pound of nitrogen per 1,000 square feet in a single application. Mowing heights and frequencies should be within the recommended range for the turfgrass species being managed. Keep the mower blades sharp to prevent open wounds through which the fungus can enter.

Reduce extended periods of leaf wetness by watering deeply but infrequently to wet the entire root zone. Do not irrigate just before or after sunrise, and ensure good surface and soil drainage. Remove unwanted vegetation that impedes air movement and prune trees to allow for light penetration. Power rake or dethatch to remove excessive thatch and reduce the potential for pathogen survival. Regular aerification and topdressing of golf greens is also necessary to reduce thatch buildup.

CHEMICAL CONTROL

Leaf spot can be controlled on a preventative or curative basis. However, applications are most effective when made in the early stages of development. Once the disease reaches the melting out stage, fungicides may not cure infected plants but will help to reduce further spread of the disease. Susceptible turfs should be monitored frequently for signs of disease activity during periods of cool and wet weather.