Melting Out or Leaf Blotch

Several fungi can cause melting out, or leaf blotch. Fungus spores produce abundantly and travel long distances by wind, water, and mowers. Infection by the wind-borne spores results in leaf spotting.

Symptoms are round or oblong spots parallel to the leaf blade. They are usually brown or purple and are more numerous near the collar area of the leaf blade. The leaf sheath turns brown and dies, resulting in death of the leaf blade. In severe cases, a sheath and crown rot kills the grass in patches. The grass may be badly thinned over the entire turf area.

Control: There are no resistant varieties. (1) Do not let grass stay wet. Irrigate early in the morning. (2) Keep the grass in good vigor. Do not apply high rates of water-soluble nitrogen fertilizers in the spring. (3) Raise mowing height during disease outbreak. (4) Remove and destroy clippings from affected lawns when mowing. (5) Apply one of these fungicides: mancozeb, quintozene, myclobutanil, thiophanate-methyl, chlorothalonil azoxystobin, polyoxin B, or trifloxystrobin.