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 | Amount per 1000 sq ft** | Ag Use REI‡ |
NonAg Use REI‡ |
|
|---|---|---|---|---|
| (Example trade name) | (hours) | (hours) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used. | ||||
| A. | CHLOROTHALONIL | |||
| (Daconil Action) | Label rates | 12 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M5) | ||||
| B. | IPRODIONE | |||
| (Chipco 26019) | 4–8 fl oz/1000 sq ft | See label | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Dicarboximide (2) | ||||
| 1 | Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. 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 a fungicide with a different mode-of-action group number. |
| ‡ | Restricted entry interval (REI) 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. |