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UC Pest Management Guidelines

Melting out disease symptoms on Kentucky bluegrass turf.


Melting Out

Pathogen: Drechslera poae

(Reviewed 9/09, updated 9/09)

In this Guideline:


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.


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.


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.


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 Example trade names Ag Use
NonAg Use
(trade name)   (hours) (hours)

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When choosing a fungicide, consider general properties as well as information relating to environmental impact.
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) 4 until dry
B. CAPTAN Captan  
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M4) 4 days until dry
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M5) 12 until dry
D. FLUDIOXONIL Medallion  
  MODE OF ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12) 12 until dry
E. IPRODIONE Chipco 26019  
  MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2) see label until dry
F. MANCOZEB Fore, Dithane M-45  
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M3) 24 until dry
  COMMENTS: Dithane M-45 registered for use on sod farms only.
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) 24 until dry
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) 24 until dry
I. THIOPHANATE-METHYL Fungo 50, T-Methyl E-Pro  
  MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1) 12 until dry
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) 12 until dry
K. VINCLOZOLIN Curalan, Touche  
  MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2) 5 days until dry
1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number.
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Agricultural use applies to sod farms and commercial seed production.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T
F. Wong, Plant Pathology, UC Riverside
M. A. Harivandi, UC Cooperative Extension, Alameda County
Acknowledgment for contributions to Diseases:
J. Hartin, UC Cooperative Extension, San Bernardino County
M. E. Grebus, Plant Pathology, UC Riverside

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