ANR-493, Repvised 2000. Austin K. Hagan, Extension Plant Pathologist, Professor, Entomology and Plant Pathology, Auburn University

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Controlling Dollarspot on Home Lawns

Dollarspot is the most widespread disease of turfgrasses in Alabama. Damage caused by this disease can be serious and is unsightly on well-maintained lawns, greens, and tees.

Bermudagrass, zoysiagrass, fine fescue, and bentgrass are all susceptible to dollarspot. This disease may also be found on centipedegrass, bahiagrass, and rarely on St. Augustinegrass. Dollarspot can be found at anytime during the growing season but is most commonly seen in late summer and early fall (Figure 1).

Figure 1. Typical dollarspot symptoms on zoysiagrass.

On closely mowed bermudagrass, zoysiagrass, or bentgrass, dollarspot appears as small, circular, tan-colored spots 1 to 2 inches in diameter. On coarser lawn grasses such as centipedegrass, spots are less distinct and somewhat larger than on fine-leafed turfgrasses. If left unchecked, these spots will grow together, forming large areas of blighted turf.

On individual diseased leaves, yellow spots appear. They later appear water soaked and finally turn tan. A distinct dark brown border always surrounds the spots on the leaves. Most often, spots appear first along the edge of a leaf and gradually expand in a broad band that may girdle the leaf blade.

The causal fungus, Sclerotinia homoeocarpa, survives as mycelium in diseased turfgrass leaves. It is spread mainly through the movement of diseased grass clippings by people, water, wind, and lawn mowers or other lawn care equipment (Figure 2).

Figure 2. Web-like mycelium of dollarspot fungus on centipedegrass leaves. Note tan-colored spot on leaf.

The causal fungus usually invades the leaves but may also damage the crown, causing deep scars in the turf. Following a heavy dew, the white web-like mycelium of the fungus may be found on the diseased turf. This mycelium quickly disappears as the leaves dry. Mycelium of other fungi or small spider webs are often confused with the mycelium of this fungus.

Wet and mild conditions within the turf canopy favor growth of the fungus. Infection occurs when fungal mycelium comes into contact with a healthy leaf.

Dollarspot is more of a problem on drought-stressed turf. Lawns receiving adequate amounts of water are less susceptible to damage. Low cutting heights and low nitrogen fertility will increase the severity of dollarspot on zoysiagrass and bermudagrass. Fog, dew, or watering will provide enough moisture for the disease to develop.

Control Measures

Maintaining recommended nitrogen fertility levels for good turf growth is often an effective control for dollarspot. Excessive nitrogen fertility levels may lead to problems with brown patch on zoysiagrass, bentgrass, and fescue lawns.

Since moisture stress also favors dollarspot development, thorough but infrequent waterings will also help control this disease. Irrigate in the late morning to early afternoon or after midnight to reduce the time the foliage remains wet. Maintain recommended cutting heights and avoid scalping turf during periods of dry weather.

Use fungicides only on lawns where dollarspot causes serious damage year after year. For detailed fungicide recommendations for dollarspot control on home lawns, see Table 1. For a complete list of recommended fungicides, see Extension publication ANR-530, "Disease and Insect Control for Commercial Turf" or ANR-500B "Alabama Pest Management Handbook--Volume 2."

For best results, begin fungicide applications as disease symptoms appear and make three to four additional applications. Apply fungicides with a hose proportioner or hand sprayer.

 Table 1. Fungicides Registered for Controlling Dollarspot on Turfgrasses

Product		Per 1,000 Sq. Ft.	Amount To Use Comments
chlorothalonil			Apply at 7- to 14-day intervals in 2 to 5 gal. of water per 1,000 sq. ft. before disease is seen. Shorten interval to 7 days and increase rate when disease appears. Golf course and sod farm use only. No residential use.
	DACONIL 2787/BRAVO 40.4F	3-11 fl. oz.
	DACONIL 2787 ULTREX	1.8-7.4 oz.
	ECHO 90DF	1.75-6.50 oz.
	THALONIL 4L	3.0-11 fl. oz.
chlorothalonil + fenarimol			Apply on a 14- to 21-day schedule. Shorten interval and increase rate when disease appears.
	BROADWAY 4.4F	3.0-4.5 fl. oz.
	TWO SOME 4.4F	3.0-4.5 fl. oz.
fenarimol			Apply at 10- to 28-day intervals in 2 to 5 gal. of water per 1,000 sq. ft. Shorten interval when disease is present.
	RUBIGAN AS	0.75-1.5 fl. oz.
iprodione			Apply at 22- to 28-day intervals in 2 to 5 gal. of water per 1,000 sq. ft.; apply every 14 to 21 days on tees and greens. No residential use.
	CHIPCO 26019 50W	1.5-2 oz.
	CHIPCO 26019 FLO	3-4 fl. oz.
propiconazole			Apply at 7- to 28-day intervals when conditions favor disease.
	BANNER MAXX	0.5-2.0 fl. oz.
thiophanate-methyl			Apply at 5- to 14-day intervals in 5 gal. of water per 1,000 sq. ft. Shorten interval and increase rate when disease appears. Use on St. Augustinegrass, bermudagrass, and cool-season turfgrasses ONLY.
	FUNGO 50 50W*	1-2 oz.
	CLEARY'S 3336 50W*	1-2 oz. (4-8 Tbs.)
	CLEARY'S 3336-F*	1-2 fl. oz.
	Systec 1998-F	1-2 fl. oz.
triademifon			Apply at 30-day intervals in 2 to 4 gal. of water per 1,000 sq. ft. When disease is present, use full rate; then reduce rate for subsequent applications.
	BAYLETON 25W	1-2 oz. (6-12 Tbs.)
myclobutanil			Apply at 14-day intervals in 1 to 3 gallons of water per 1,000 sq. ft.
	Eagle 40W	0.5-1.2 oz.
	IMMUNOX	14 fl. oz.
*Not cleared for use on zoysiagrass and centipedegrass.

Use pesticides only according to the directions on the label. Follow all directions, precautions, and restrictions that are listed. Do not use pesticides on plants that are not listed on the label.

The pesticide rates in this publication are recommended only if they are registered with the Environmental Protection Agency and the Alabama Department of Agriculture and Industries. If a registration is changed or cancelled, the rate listed here is no longer recommended. Before you apply any pesticide, check with your county Extension agent for the latest information.

Trade names are used only to give specific information. The Alabama Cooperative Extension System does not endorse or guarantee any product and does not recommend one product instead of another that might be similar.

For more information, contact your county Extension office. Look in your telephone directory under your county's name to find the number.