Ohio State University Extension Fact Sheet

Plant Pathology

2021 Coffey Road, Columbus, OH 43210-1087

Dollar Spot on Turfgrass

HYG-3075-96

Joseph W. Rimelspach
Michael J. Boehm

Dollar spot occurs on essentially all cultivated turfgrass species worldwide. In Ohio it is primarily a concern on low cut creeping bentgrass on golf courses although it may be prevalent in lawns on bluegrass and fine fescue. Dollar spot occurs from late spring to late fall and is most prominent after cool moist weather.

Dollar spot on bluegrass.	Hourglass-shaped tan lesions on bentgrass leaf blades.

Causal Organism

Dollar spot is caused by the fungus, Sclerotinia homoeocarpa. This fungus produces resting bodies called stomata which may live for long periods on grass clippings, in thatch, or in soil. The taxonomic classification of this fungus is currently under revision so don't be alarmed if you see it being called by other names such as Lanzia or Moellerodiscus. Temperatures between 60 and 85 degrees F and long periods of leaf wetness from dew, rain or sprinkler irrigation favor growth of this fungus. Prolonged wet foliage is a key factor. Growth of the dollar spot fungus is inhibited when temperatures exceed 90 degrees F. Spread of the pathogen to new areas occurs primarily by wind and water. Turfgrass growing under dry soil conditions is more susceptible than when adequate soil moisture is provided. Damage is usually more severe if there is a deficiency or great excess of nitrogen. Soil pH does not affect disease development.

Symptoms

The first symptoms of the disease appear as tiny yellow spots on individual grass blades. The spot expands to a straw colored or tan band with dark reddish-brown margins. The tip of the affected leaf often remains green. The tan band, or lesion, is often narrower in width than the leaf, resulting in the lesion taking on an "hourglass" shape. The entire blade soon becomes bleached. As the grass dies and the infected areas enlarge, light straw-colored spots 2 to 3 inches in diameter appear in the lawn. A fine, cobwebby white mold may be visible early in the morning when heavy dew is present. This mycelial growth of the fungus will disappear as the turf dries. The turf in these spots may be killed all the way from the lesion to where the plant comes into contact with the soil. If left unchecked, the spots may merge and form large, irregular straw-colored patches. On low cut turf, such as that on golf greens and fairways, the spots are often well defined and smaller than those on high cut residential or commercial turf and as the name implies are about the size of a silver dollar. Thus, the descriptive term "dollar spot.'

Management

1. Adequate fertilizer program. Proper nitrogen fertility will greatly reduce the occurrence and severity of dollar spot. Refer to Home Yard and Garden fact sheet 4006, "Fertilization of Lawns." Note: Careful consideration must be given to fertility programs to avoid excessive nitrogen fertility which aggravates other diseases such as Brown Patch.

2. Avoid periods of prolonged leaf wetness. Avoid over watering and frequent late afternoon or evening irrigation that prolongs the time grass stays wet. This is especially true for mornings when heavy dew is likely. Prune trees and shrubs to facilitate optimal penetration of sunlight and remove barriers or wind blocks to promote optimal air movement so grass dries faster.

3. Irrigate turf during dry conditions. Provide adequate soil moisture for continuous and optimal turf growth.

4. Select resistant cultivars. Before seeding, consider recommended cultivars that are resistant to dollar spot. This is especially helpful when planting Kentucky bluegrass.

5. Chemical control used early in disease development can be quite successful. Once dollar spot gains a foothold and is widespread, chemical management will be difficult.

Please refer to The Ohio State University Bulletin L-187, Control of Turfgrass Pests for the most current recommendations for the management of dollar spot on turf. This publication can be obtained from your county Extension office or the Extension Publications Office, The Ohio State University, 385 Kottman Hall, 2021 Coffey Road, Columbus, Ohio 43210-1044; phone (614) 292-1607.

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