Large Patch aka Brown Patch Disease Killing my Lawn

I consider myself a nosey neighbor, I secretly noticed all my neighbors lawn problems. I even saw one neighbor sharing his Sevin insecticide with the other to control brown patch which is a fungus. Warm weather in our area makes the condition favorable for Large patch lawn disease. Large patch formerly known as brown patch can be very damaging to warm season grasses such as St. Augustine, zoysia and Bermuda. The disease thrives very well in temperatures below 80 degrees Fahrenheit. The outcome of the affected lawn will depend on cultural practices such as your fertilizer program, water schedule, and even mowing practices. Excessive nitrogen fertility and thatch often contribute to the disease infestation, therefore, it is important to reduce the amount of fertilizer applied. Irrigation also contributes to the proliferation of large patch, therefore it is important to follow the irrigation recommendation that suggests that it is best to water early morning before 10 am and not late evenings as frequently practiced. Watering late evening allows the grass to stay wet for long overnight period which facilitates the severity of disease. In addition, using a lawn mower that cuts other premises and is not sanitized can also spread the disease to your lawn.

Symptoms- The disease is first evident at the base of the leaf blades close to the soil where the leaf begins to turn light yellow, rots, and can easily be pulled. The disease most often occurs as a circular patch ranging from few inches to few feet in diameter with a dark outer ring. The grass will die rapidly if conditions such as high humidity, high nitrogen fertility, and wetness remains and the affected area is not treated. Weeds often grow in the dead area.

Treatment- It is less expensive to prevent large patch than to treat it. Prevent large patch by ensuring that the soil is properly drained, avoid planting St. Augustine in shade, reduce the amount of nitrogen fertilizer, and do not water in late evening. There are many fungicides that are available on the market that are very effective in controlling large patch. It is important to note that if the same pesticide, or class of pesticide, is applied repeatedly on the same site over a period of time, the fungus will become resistant and lose effectiveness to that fungicide. There are many brands of fungicides on the market, however the active ingredient of the fungicide is more important than brand names. The following are only few of the many active ingredients that are available to control large patch; azoxystrobin, fluoxastrobin, pyraclostrobin, thiophanate-methyl, flutolanil and propiconazole. It is also a good practice to purchase fungicides that have a combination of ingredients for greater efficacy. It is always important to read the label to ensure that product is labelled specifically for the desired pest. It easy to incorrectly identify diseases, therefore it is recommended to send sample to the UF/IFAS Extension laboratory for proper identification.

This article is only a brief overview, for more information or for questions on horticulture you are encouraged to contact Grantly Ricketts at UF/IFAS Extension in Osceola County at or by phone 321-697-3000.


Posted: September 25, 2019

Category: Florida-Friendly Landscaping, Horticulture, Turf
Tags: Turf Disease

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