Brown Patch Lawn Disease
Scientific Name: Rhizoctonia solani
Disease development is favored by nighttime temperatures above 70˚, high humidity, and/or a thin film of moisture.
Brown patch develops rapidly (24-48 hrs.) during warm, humid weather. It is a foliar-disease that does not affect crowns or roots. In some cases, brown patch occurs as distinct circular patches of blighted turf from a few inches to several feet in diameter. Diseased turf may appear droughty even though sufficient moisture may be present. Symptoms on individual plants appear as irregular, water soaked spots on the leaves. The spots are bordered by dark, brown band. Thin strands (mycelium) of fungus can sometimes be seen in early morning between diseased leaves.
1. Maintain proper amounts of nitrogen. Apply the majority of nitrogen in the fall and do not over-fertilize. Do not apply more than 4 lbs. of actual nitrogen per 1,000 sq. ft. per year.
2. Do not irrigate in late afternoon or evening. The longer the leaves remain wet increases the likelihood of brown patch development. Irrigation after midnight to mid-morning is preferable.
3. Don’t apply nitrogen fertilizer when brown patch is active; however a light fertilization (less than 1/4 lb. per 1,000 sq. ft.) after a brown patch epidemic may speed recovery.
4. Avoid seeding rates greater than 6-8 lbs. per 1,000sq.ft. This makes it physically easier for the fungus to move from leaf to leaf (excess number of plants).
Fungicides may be applied as a preventative (provides 2-3 week suppression). Two to three applications may be required for season-long control. Begin preventative treatments in early-mid June. A curative program (apply fungicide as soon as symptoms appear; some turf damage has occurred) will suppress further disease development. Several fungicides are labeled for control of brown patch.
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