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How to Manage Pests

UC Pest Management Guidelines


Sclerotium blight damaged areas on mixed species turf; photo shows characteristic ring shape of infested areas.

Turfgrass

Sclerotium Blight (Southern Blight)

Pathogen: Sclerotium rolfsii

(Reviewed 6/03, updated 6/03)

In this Guideline:


DESCRIPTION OF THE DISEASE
Sclerotium blight affects circular areas of turf, enlarging up to 9 feet in diameter; some plants may remain alive in the centers of these areas. Sometimes only partial circles or crescent-shaped areas of affected turf are seen. The turfgrass turns reddish brown as it dies. Infected plants appear completely necrotic. As the fungus advances, abundant white mycelia appear on the turfgrass. Light to dark brown sclerotia, which are tiny, hard, resting bodies that resemble mustard seeds, develop at the base of the stems and may help identify this disease.

SUSCEPTIBLE TURFGRASSES
Bentgrasses, bluegrass, fescues, ryegrasses, dichondra are susceptible to southern blight.

CONDITIONS FAVORING DISEASE
The fungus survives in thatch as sclerotia. Spread is by sclerotia and infected plant parts. The disease is favored by warm or hot weather, high moisture, and heavy thatch. Initial infections commonly occur in late spring, when air temperatures rise above 75°F; several days of drought followed by high soil moisture appears to be conducive to high levels of sclerotia germination. Optimal conditions for disease development are air temperatures of 85° to 95°F coupled with high moisture in the thatch layer from precipitation, high humidity, or over irrigation.

MANAGEMENT
Prevent the development of sclerotium blight by following good cultural practicies. Fungicides may be necessary in areas where this disease is chronic.

Cultural Control
The disease appears to be less destructive on well fertilized, vigorously growing grass. Control thatch and use good sanitation practices around equipment, because both aerifying and verticutting can spread the fungus sclerotia. Avoid overirrigation.

Treatment Decisions
In areas where southern blight is chronic, fungicide applications can be made in late spring before the development of symptoms; otherwise, apply fungicides soon after symptoms are seen.

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. FLUTOLANIL Oxathiin
     
C. TRIADIMEFON DMI

[Precautions]

PUBLICATION

[UC Peer Reviewed]

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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Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2005 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See How to manage pests, or in the U.S., contact your local Cooperative Extension office for assistance. /PMG/r785100911.html revised: May 20, 2005. Contact webmaster.