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Dollar Spot in Home Lawns

Ned A. Tisserat
  Extension Specialist, Plant Pathology

 

Symptoms

Dollar spot is a common problem on most turfgrasses grown in Kansas, including Kentucky bluegrass, perennial ryegrass, buffalograss, bermudagrass, and zoysiagrass. It is not common on tall fescue. The disease may occur regardless of management or soil fertility, although damage usually is most severe if there is a deficiency of nitrogen. Dollar spot results in the formation of small, roughly circular, bleached patches in the lawn. The patches are more numerous in areas where there is poor air circulation or drainage. Most spots are only a few inches in diameter. However, under favorable environmental conditions and mowing heights greater than two inches, individual spots may exceed 6 inches in diameter. Affected plants within the diseased spots wilt and eventually turn tan or brown. During outbreaks of the disease, numerous spots on the turfgrass coalesce into large irregular dead areas. This can result in substantial damage to the turfgrass.

 

dollarspothomefigure1forWeb.jpg (182501 bytes)

DollarSpotZoysiaFig2forWeb.jpg (194809 bytes)

Figure 1.  Dollar spot on Kentucky
bluegrass.

Figure 2.  Dollar spot on zoysiagrass.


On individual infected plants, leaves develop light yellow to tan lesions with reddish-brown borders. On cool-season grasses, such as tall fescue and Kentucky bluegrass, lesions normally are located near the middle of the leaf and extend completely across the leaf blade. The bleached area is bordered by dark red to brown margins or lines, which are characteristic of dollar spot. On warm-season grasses (bermudagrass, buffalograss, and zoysiagrass) the bleached zones on leaves may be more numerous and smaller, but are still bordered by brown bands. In the early morning when dew is still present on the turfgrass, small cottony strings of the fungus can sometimes be seen growing from the diseased leaf blades. This growth can be confused with spider webs, "cotton" from plant seeds, or other fungi, and therefore is not a reliable diagnostic feature.

 

Dollar spot lesions on bermudagrass leaves

dollarspothomebermudagrass figure4forWeb.jpg (122506 bytes)

Figure 3. Dollar spot lesions on
bermudagrass leaves

Figure 4.  Growth of dollar spot
fungus on bermudagrass.

 

Symptoms

The fungus (Sclerotinia homoeocarpa) that causes dollar spot survives indefinitely in thatch and soil. In the presence of a thin film of moisture on leaves and favorable temperatures, the fungus will begin to grow and infect leaves. The fungus rarely infects the roots, although fungal toxin produced may affect root formation. Dollar spot is most severe in late spring and early summer and again in early fall; however, it can occur throughout the summer months.



Disease Management

Dollar spot is more prevalent in nitrogen deficient turf. One of the simplest methods to reduce or avoid dollar spot on cool-season turfgrasses is to maintain an adequate nitrogen fertilization program. Don't overfertilize, since this can result in an increase of other turfgrass diseases, such as brown patch. Consult Extension publications on lawn fertilization for more complete information. Avoid night watering or other irrigation practices that allow the leaves to remain wet for long periods.

Dollar spot is rarely serious enough on home lawns to require fungicide treatments. Nevertheless, dollar spot can reduce the aesthetic quality of the turf for short periods. Fungicides applied as soon as symptoms are noted on the plants will effectively suppress disease development.

Fungicides listed in the table will adequately control dollar spot. Some of the products listed are not readily available to homeowners.

 


Fungicides Labeled for Dollar Spot Control
Fungicide Efficacy Typical Application Interval (days) Examples of Product Names
iprodione

good-excellent

14-28

 Chipco 26019, Chipco GT, Fungicide X
mancozeb

good

7-14

 Fore, Dithane, Formec, Mancozeb, Protect
myclobutanil

good

14

 Eagle, Immunox
propiconazole

good

14

 Banner, Fertilome
Systemic fungicide
thiophanate-methyl

good-excellent

10-21

 Benomyl, Cleary's 3336, Cavalier, Fungo, SysTec 1998
triadimefon

good-excellent

14-28

 Accost, Bayleton, Fungicide VII, Fungi-Fighter, others
thiram

good

14

 Spotrete, Lawn Disease Control, Thiram

 

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Web updated 9/01/06
Web comments to jpierz@ksu.edu