Description of the Disease
Fusarium blight first appears as small, circular, grayish green areas, ranging from a few inches up to a foot in diameter. Some plants in the center of the circles may survive, giving them a frog eye or donut appearance. The crown or basal area of the dead stems is affected with a reddish rot and is hard and tough. At times, a pink layer of the fungus can be seen near the soil line. The dead foliage appears bleached. The fungus survives as mycelia in plant debris and plants killed by previous infections, or as thick-walled resting spores (chlamydospores) in the thatch and soil.
Susceptible Turfgrasses
Fusarium blight can affect a number of cool-season grasses grown in warm weather conditions including bentgrasses, red fescue, tall fescue, perennial ryegrass and centipedegrass, but is most severe on Kentucky bluegrass. For Kentucky bluegrass, the most susceptible cultivars are Park, Campus, Fylking, and Nugget. A-34, Baron, Merion, Victa, Windsor, and the newer cultivars such as Adelphi, Bonnieblue, Geronimo, Majestic, Parade, and Rugby, are much less susceptible.
Conditions Favoring Disease
The disease is favored by daytime temperatures of 85°to 95°F and night temperatures of 70°F or above.
Management
Fusarium blight occurs most commonly in areas that have been stressed for moisture and in areas in full sun. Follow proper irrigation and fertilization practices and regularly dethatch the turfgrass. Fungicides may be required if the turfgrass has a history of Fusarium blight, but complete control is difficult to achieve with fungicides.
Cultural Control
Follow recommended irrigation scheduling practices based on evapotranspiration need of the turfgrass to avoid moisture stress. Because the disease is also worse under excessive nitrogen, recommended fertilization practices should also be implemented. Use 20% perennial ryegrass when seeding bluegrass, and choose resistant varieties. Low cutting heights on golf courses may worsen infestation, as well as excessive thatch.
Treatment Decisions
The crown and basal rot associated with Fusarium blight is difficult to control with fungicides. If using fungicides with little or no systemic activity (iprodione), apply them preventively when environmental conditions favor the development of the disease. Systemic fungicides can be used either at this same time, or soon after symptoms begin to appear.
| Common name | Amount to use | 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. | IPRODIONE | |||
| (Chipco 26019) | 8 fl oz/1000 sq ft | See label | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Dicarboximide (2) | ||||
| B. | MYCLOBUTANIL | |||
| (Eagle 20EW) | 1.2–2.4 fl oz/1000 sq ft | 24 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) | ||||
| C. | PROPICONAZOLE | |||
| (Banner Maxx) | 2–4 fl oz/1000 sq ft | 12 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) | ||||
| D. | THIOPHANATE-METHYL | |||
| (Fungo Flo) | Label rates | 12 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1) | ||||
| E. | TRIADIMEFON | |||
| (Bayleton 50 Turf and Ornamental) | Label rates | 12 | Until dry | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) | ||||
| COMMENTS: Provides the most effective control. | ||||
| 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. |