How to Manage Pests
UC Pest Management Guidelines
Pathogens: Fusarium culmorum, F. tricinctum
(Reviewed 9/09, updated 9/09, pesticides updated 12/16)
In this Guideline:
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.
Fusarium blight can affect a number ofcool-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.
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.
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.
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.
UC IPM Pest Management Guidelines: Turfgrass
A. Downer, UC Cooperative Extension, Ventura County
Acknowledgment for contributions to Diseases:F. Wong, Plant Pathology, UC Riverside
J. Hartin, UC Cooperative Extension, San Bernardino County
M. E. Grebus, Plant Pathology, UC Riverside