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How to Manage Pests
UC Pest Management Guidelines
Turfgrass
Sclerotium Blight (Southern Blight)
Pathogen: Sclerotium rolfsii
(Reviewed 6/03,
updated 6/03)
In this Guideline:
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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.
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| A. |
AZOXYSTROBIN |
QoI (strobilurins) |
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| B. |
FLUTOLANIL |
Oxathiin |
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| C. |
TRIADIMEFON |
DMI |
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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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