How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE DISEASE

Curvularia blight causes thinning out and decline of the grass; irregular patches and streaks may also occur. Leaves yellow and then become brown from the leaf tip down. Leaf spots can occur with symptoms most severe on older, senescing leaves. Roots, stolons and rhizomes may also become infected. A fine, grey layer of mycelia may cover infected tissues, and there is often an abundance of sporulation from infected and dead tissue. Spores are borne on the mycelia and no enclosed fruiting structures are formed.

SUSCEPTIBLE TURFGRASSES

Annual bluegrass, bermudagrass, bentgrass, and fescue are susceptible to curvularia blight.

CONDITIONS FAVORING DISEASE

The pathogen invades grasses through cut tips of leaves and is favored by high temperatures and adverse growing conditions. This is primarily a stress pathogen that attacks low fertility and heat and drought stressed plants. Damage often occurs when temperatures are 85°F or higher.

MANAGEMENT

To prevent conditions that can lead to the development of curvularia blight, avoid both overwatering and drought stress by irrigating according to evapotranspiration needs of the turfgrass. Fertilize to promote moderate growth. Maintain as high a mowing height as possible and control thatch. Avoid planting shade trees in the surrounding area. Fungicides may be warranted on golf greens during long periods of high temperatures.

Cultural Control
Cultural practices can be important in preventing development of this disease. Apply the correct amount of fertilizer, reduce soil compaction, provide good soil drainage, and manage the thatch layer to keep it under 0.5 inches in thickness.

Treatment Decisions
There is little fungicide efficacy data available for the control of curvularia diseases in California. Both chlorothalanil and iprodione have been shown to be effective in other states.

Common name		Example trade names	Ag Use R.E.I.+	NonAg Use R.E.I.+
(trade name)			(hours)	(hours)
When choosing a fungicide, consider general properties as well as information relating to environmental impact.
A.	CHLOROTHALONIL	Daconil
	MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M5)		12	until dry
B.	IPRODIONE	Chipco 26019
	MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2)		see label	until dry
1	Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number.
+	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Agricultural use applies to sod farms and commercial seed production.

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 County
Acknowledgment for contributions to Diseases:
J. Hartin, UC Cooperative Extension, San Bernardino County
M. E. Grebus, Plant Pathology, UC Riverside

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