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How to Manage Pests

UC Pest Management Guidelines


Melting out disease symptoms on Kentucky bluegrass turf.

Turfgrass

Melting Out

Pathogen: Drechslera poae

(Reviewed 6/03, updated 6/03)

In this Guideline:


DESCRIPTION OF THE DISEASE
Melting out causes circular to elongated purplish or brown spots with straw-colored centers on leaf blades, leaf sheaths, and stems. The leaf spots may be widespread throughout the lawn, indicating spread by windborne spores. Crowns and roots are frequently affected with a dark brown rot. The crown-infected plants are weakened and may die in hot, windy weather, resulting in a thinning out of the turf in scattered areas. The fungus survives on infected bluegrass plants or grass debris and may be seedborne.

SUSCEPTIBLE TURFGRASSES
Kentucky bluegrass is highly susceptible to melting out. Many improved bluegrass selections are resistant, including: Adelphi, Bristol, Destiny, Eclipse, Enmundi, Glade, Ikone, Liberty, Majestic, Mona, P-104, Rugby, and Somerset.

CONDITIONS FAVORING DISEASE
Cool (50° to 75°F), moist conditions favor melting out. Symptoms first appear on shaded plants. Melting out is most severe on closely mowed turf and on turf with high nitrogen fertilization.

MANAGEMENT
To prevent the development of melting out, follow good management practices. Reduce shade, improve soil aeration and water drainage, and control thatch. Avoid dry spots and maintain as high a cutting height as feasible. Apply recommended rates of nitrogen fertilizers. Select resistant cultivars. With the use of resistant cultivars and other recommended cultural management practices, fungicides should not be necessary in most situations. For susceptible cultivars, treat at the onset of symptoms.

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

[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
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