St. Augustine and Empire Zoysia can be affected by Large Brown Patch disease.
This lawn disease is often observed from November through May when temperatures are below 80°F. It is normally not observed in the summer months. 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. The disease infects the leaf area closest to the soil, eventually killing the leaf. A soft, dark rot occurs at the base of the leaf and leaves and can easily be pulled off the stem. The base of a pulled leaf has a rotted odor. Roots are not affected by this pathogen. The disease usually begins as small patches (about 1 foot in diameter) that turn yellow and then reddish-brown, brown or straw colored as the leaves start to die. Patches can expand to several feet in diameter. It is not uncommon to see rings of yellow or brown turf with apparently healthy turf in the center. Turf at the outer margin of a patch may appear dark and wilted. This disease is often confused with herbicide 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 sheath, but the base of the leaf is not dark and rotted. Instead, the leaf base is dry with a tan discoloration and there is no distinct smell of rot. Cultural practices, involving nutrient and water management, can be adjusted to control Brown patch. Excessive nitrogen application during potential disease development. His should be avoided. 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 in nitrogen, preferably a slow release potassium form, should be applied.
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