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UC Pest Management Guidelines

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Turfgrass

Red Thread

Pathogen: Laetisaria fuciformis

(Reviewed 6/03, updated 6/03)

In this Guideline:

Description of the disease
Susceptible turfgrasses
Conditions favoring disease
Management

DESCRIPTION OF THE DISEASE
Red thread may kill turfgrass in patches that are 2 to 8 inches in diameter, or the disease may occur over large areas without killing the plants. A pink web of fungal threads binds the leaves together. Look for pink, gelatinous fungal crusts projecting from the leaves to help identify this disease.

SUSCEPTIBLE TURFGRASSES
Bentgrasses, bluegrasses, fescues, ryegrasses, and bermudagrasses are susceptible to red thread.

CONDITIONS FAVORING DISEASE
This disease occurs most frequently along the coast of northern and central California but may be found in southern California on rare occasions. The disease is common under conditions of mild air temperatures (60° to 75°F) and extended periods of leaf wetness. It often appears on plants deficient in nitrogen during periods of cool or warm temperatures if there is adequate moisture (excess irrigation or rainfall).

MANAGEMENT
Providing proper irrigation and fertilization can reduce the incidence of red thread. Adequate nitrogen can usually prevent this disease from occurring. Prevent drought stress by irrigating turfgrass based on evapotranspiration needs of the turfgrass. Provide adequate air circulation and reduce shading. Fungicides are rarely warranted except in severe cases.

Common name Chemical class

Many of these products are available for use by licensed applicators only and cannot be used by home gardeners.

A. AZOXYSTROBIN QoI (strobilurins)

B. CHLOROTHALONIL Chlorophenyl (multi-site)

C. FENARIMOL DMI

D. FLUTOLANIL Oxathiin

E. IPRODIONE Dicarboximide

F. MANCOZEB EDBC (multi-site)

G. MYCLOBUTANIL DMI

H. PROPICONAZOLE DMI

I. THIOPHANATE-METHYL Benzimidazole

J. TRIADIMEFON DMI

K. TRIFLOXYSTROBIN QoI (strobilurins)

L. 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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