DESCRIPTION OF THE DISEASE
Leaf spot occurs on leaf blades, sheaths, and stems as circular to elongated purplish or brown spots with brown colored centers and purplish to dark brown borders. Spots may be found on turfgrass leaves throughout the site, indicating spread by windborne spores. Crown and roots are frequently affected with a dark brown rot. Plants with crown infections are weakened and may die in hot, windy weather, resulting in a thinning out of the turf in scattered areas.

SUSCEPTIBLE TURFGRASSES
Bentgrasses, bluegrasses, fescues, and ryegrasses are susceptible to leaf spot. The fungus survives in infected grass plants or grass debris and may be seedborne. Spores are airborne.

CONDITIONS FAVORING DISEASE
The disease is favored by warm temperatures (70° to 90°F), high humidity, extended leaf wetness, and closely cropped turfgrass. It is more severe under high nitrogen fertilization.

MANAGEMENT
Follow good management practices to prevent the development of leaf spot. Fungicides are usually not warranted.

Cultural Control
Reduce shade and improve soil aeration and water drainage. Avoid dry spots, overfertilizing with nitrogen, and maintain as high a cutting height as possible. Avoid prolonged leaf wetness by irrigating in pre-dawn, or early morning hours. If possible, increase air movement.

Treatment Decisions
Leaf spot usually is not serious enough in California to warrant the use of fungicides although they may be used in areas where leaf spot is severe.

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. CAPTAN Pthalamide (multi-site)

C. CHLOROTHALONIL Chlorophenyl (multi-site)

D. FLUDIOXONIL Phenylpyrrole

E. IPRODIONE Dicarboximide

F. MANCOZEB EDBC (multi-site)

G. MYCLOBUTANIL DMI

H. PROPICONAZOLE DMI

I. THIOPHANATE-METHYL Benzimidazole

J. TRIFLOXYSTROBIN QoI (strobilurins)

K. 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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