How to Manage Pests

UC Pest Management Guidelines

SUSCEPTIBLE TURFGRASSES
Bentgrass, bermudagrass, fescue, ryegrass and annual bluegrass can be affected, but closely mowed grasses of any of these species are most susceptible to the disease.

CONDITIONS FAVORING DISEASE
Dollar spot is most common during the spring and fall months in California, especially on annual bluegrass, Kentucky bluegrass, and creeping bentgrass used in coastal plantings. Disease development is favored by moderate temperatures (60° to 80°F) with high relative humidity. Excessive leaf wetness and fog contribute to disease development as do water stress and excess thatch development. Dollar spot is primarily a problem on golf courses and lawn bowling greens.

MANAGEMENT
Proper fertilization and irrigation as well as adding compost are important in preventing the development of dollar spot. Fungicides may be necessary to provide control if the disease develops.

Cultural Control
Turfgrass deficient in nitrogen tends to develop more dollar spot than turfgrass adequately fertilized. Apply recommended amounts of nitrogen and maintain adequate air circulation. Keep thatch to a minimum. Irrigate based on evapotranspiration needs of the turfgrass to a depth of 4 to 6 inches, but avoid creating drought stress by extending the interval between irrigations too long. Raise the mowing heights as much as possible.

Avoid prolonged leaf wetness by irrigating in the morning or early afternoon rather than later in the day. Remove morning dew with a light irrigation or poling. Poling involves dragging the surface of the turf with a long bamboo or plastic pole, or with an irrigation hose, to remove the dew from the grass leaves. Some varieties of creeping bentgrass show higher levels of tolerance to this disease than others. Varieties such as Putter, Emerald, Forbes 80-12, SR-1020, Penneagale, Penncross, Century and Crenshaw are quite susceptible to dollar spot, while varieties such as L-93, A-1, Providence and Pennlinks have shown tolerance to this disease.

Adding composted top dressings has been shown to reduce the incidence and severity of dollar spot, allowing a reduction in the frequency and/or application rates of fungicides.

Treatment Decisions
Apply fungicides when environmental conditions favor the development of the disease, or when the first symptoms are detected. Apply until environmental conditions are no longer favorable for the disease.

Resistance to benzimidazole and DMI fungicides has been reported in a number of locations in the United States. Benzimidazole resistance usually manifests as a loss of acceptable control with the fungicide, while DMI resistance is seen as a need for higher application rates and shorter application intervals. Alternate the use of fungicides from different chemical classes to slow the development of resistance to any one given fungicide.

Common name		Chemical class
Many of these products are available for use by licensed applicators only and cannot be used by home gardeners.
A.	CHLOROTHALONIL	Chlorophenyl (multi-site)
B.	FENARIMOL	DMI
	COMMENTS: Use with caution on bluegrass species.
C.	IPRODIONE	Dicarboximide
D.	MYCLOBUTANIL	DMI
E.	PROPICONAZOLE	DMI
F.	SULFUR	Sulfur (multi-site)
G.	THIOPHANATE-METHYL	Benzimidazole
H.	TRIADIMEFON	DMI
I.	TRIFLOXYSTROBIN	QoI (strobilurins)
J.	VINCLOZOLIN	Dicarboximide

PUBLICATION

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T
Diseases
F. Wong, Plant Pathology, UC Riverside
M. A. Harivandi, UC Cooperative Extension, Alameda Co.
J. Hartin, UC Cooperative Extension, San Bernardino Co.
Acknowledgment for contributions to the disease section:
M. E. Grebus, Plant Pathology, UC Davis

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