Brent Jeansonne, Adusumilli, Naveen
Brown Patch Disease:
This disease is most likely to be observed when temperatures are below 80°F. Infection is triggered by rainfall, excessive irrigation, or extended periods of high humidity resulting in the leaves being continuously wet for 48 hours or more. That’s why it’s important to NOT water the lawn in the evenings or night.
Symptoms/Signs: The fungus infects the leaf area closest to the soil and will eventually kill the leaf. A soft, dark rot will occur at the base of the leaf and leaves where the leaf can easily be pulled off the stem. The base of a pulled leaf has a rotted and will have an odor. The good thing is that the roots are not affected by this pathogen. Brown Patch Disease will usually begin as small patches (about 1 ft. in diameter) that will turn yellow and then reddish brown, brown, or straw colored as the leaves start to die. The patches will typically expand to several feet in diameter. It is not uncommon to see rings of yellow or brown turf with reoccurring healthy turf in the center. Turf at the outer margin of a patch may appear dark and wilted. The disease is often mistaken for herbicide or even fertilizer damage on St. Augustine grass. Herbicide damage may cause the same overall symptoms of yellow or brown patches. The leaf may still pull out of the leaf sheath, but the base of the leaf is not dark and rotted. Instead, the leaf base will be dry with a tan discoloration and there will be no distinct smell of rot.
Cultural Controls: The two most important means of cultural practices to control brown patch are nutrient and water management.
Nutrient Management: When you have excessive nitrogen or apply nitrogen during potential disease development periods a problem is most likely to occur. As a precaution, just prior to or during disease development periods, slow-release nitrogen sources should be used as opposed to readily available forms, such as soluble liquids or quick-release nitrogen sources. A balanced fertilizer containing equivalent amounts of potassium and nitrogen, preferably a slow-release potassium form should be applied.
Water Management: Irrigation should only occur when necessary and during in the early morning hours (between 4:00 and 8:00 a.m.) when dew is already present. Diseased areas should be mowed last and clippings removed carefully since mowers can spread this disease. The mower should be washed of all turf clippings before proceeding to the next site.
Chemical Controls: The most effective and assured method of complete control of brown patch is with the proper use of fungicides. Fungicide options include: azoxystrobin, chlorothalonil, fludioxonil, flutolanil, iprodione, Junction®, mancozeb, metconazole, myclobutanil, polyoxin D, propiconazole, pyraclostrobin, thiophanate-methyl, thiram, triadimefon, trifloxystrobin, triticonazole, and vinclozolin.