Large patch or brown patch - which is it? The question could be, what are they?
These are names of a disease that attacks turfgrass. Both of these diseases are caused by the same fungus, called Rhizoctonia.
In the past, we called this disease brown patch. Now, plant pathologists have divided the disease into two groups.
If the disease attacks warm-season grasses such as centipede, bermudagrass, zoysia and St. Augustine, it is called large patch. If it attacks cool-season grasses such as ryegrass and fescue, it is called brown patch.
In our area, we mainly grow warm-season grasses, so I will refer to the disease as large patch. The symptoms of large patch are circle-shaped areas in the lawn that turn yellow, then brown. These areas will get larger and can grow together. Early in the morning, you can see a grayish smoky-colored ring in the area where the diseased grass and healthy grass meet.
Large patch is a disease that occurs in the spring and fall. It likes to grow when the daytime temperature is higher than 80 degrees and the nighttime temperature is higher than 55 degrees.
Why is large patch such a problem in the spring and fall of the year? This is the time of the year when turfgrasses are coming out of or going into dormancy. The grasses are not growing as actively as during other times of the year and are more stressed, and thus are more likely to get a disease.
The best way to reduce the chance of your grass getting a disease is to properly manage your turf. There are several management practices that you can use to reduce the chance of large patch.
The first is proper irrigation. Rhizoctonia likes excess water. You can reduce the incidence of large patch by allowing your lawn to dry out before watering.
Our turfgrasses need an inch of water per week to grow properly. To encourage a deep root system, I recommend that you put all of this water on at one time. In order for Rhizoctonia to grow, the fungus needs moisture for 16 hours. This is why we recommend that you irrigate your grass early in the morning.
When you water late in the afternoon, the grass will dry the next morning around 10 o'clock. This is approaching the 16 hours needed for disease development. Also, watering your grass every other day doesn't allow the grass to fully dry out before you wet it again.
The second practice that can help reduce the chance of large patch is proper fertilization. The Rhizoctonia fungus likes and needs nitrogen to reproduce. By applying the right amount of fertilizer at the right time, you can reduce the incidence of large patch.
Turfgrass will lose a part of its root system every winter. This is why grasses are at their weakest when they are coming out of dormancy. If you apply nitrogen fertilizer too soon, you can stress the grass, which makes it more susceptible to diseases.
Our warm-season grasses are growing their best when soil temperatures reach 65 degrees. In our area, that usually occurs around late April to the first of May. This is the time to fertilize.
This is especially true of centipede and St. Augustine grass. When these grasses are fertilized too early, they turn yellow from stress. The nitrogen in the fertilizer is causing more top growth than the root system can support. The grass becomes stressed, and large patch can start. If you apply more than 1 pound of nitrogen per 1,000 square feet, you are applying too much fertilizer. The coverage rate on the bags of fertilizer is set at the 1 pound of nitrogen rate.
Diseases in your lawn can be reduced by following these two simple steps. You also can help stop large patch from becoming a problem by applying fungicides to stop diseases before they start. Most of the fungicides used by homeowners have a preventive rate listed on the label. Usually, this is one-half the curative rate. You need to read the label to determine if the fungicide you are using allows for preventative use.
By following proper irrigation and fertilization practices, you can reduce the chance of your grass getting a disease.
Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at email@example.com. The extension's Web address is www.ugaextension.com/columbia.
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