SIGNALS BROWN PATCH
Dr. William M. Johnson
Lawn grasses in the Texas Upper Gulf Coast region, especially St. Augustine, have taken a pounding over the summer from dry weather, chinch bugs, and white grubs.
With the onset of cooler temperatures and rainy weather, there is the possibility of yet another threat to the health of area lawns. The menace is known as brown patch which is a disease caused by a fungus.
The good news is that brown patch does not present as widespread a problem as that imposed by overly wet or very dry weather conditions. The not so good news is that because area lawns have been so stressed throughout the year, they are more subject to brown patch problems. If brown patch was a problem in your lawn in previous years, then it's especially likely to again be a problem this fall given the stressful growing conditions this year.
The moist conditions of fall with its mild days and cool nights are ideal for the development of brown patch. The disease occurs most consistently in the fall but it may also appear in the spring. St. Augustine is the most common lawn grass affected, but bermudagrass and zoysiagrass are also susceptible under certain conditions.
Affected patches of this lawn-devastating disease are brown in color and circular in shape but may become irregular as diseased areas enlarge and merge. They range in size from small spots during the early stage of development to areas over 50 feet in diameter later in the season.
In addition to circular patterns of brown grass, brown patch can be identified by the ease in which yellowing leaves can be readily pulled from the stolon or main stem. Select yellowing leaf samples from the outer edge of an affected area for the "pull test." As affected areas enlarge, new green growth may develop toward the center of the patch, causing a donut-shaped appearance.
The disease is most easily controlled when symptoms become first evident but early infections can go unnoticed unless regular inspections of the lawn are made. Of course, symptoms are most apparent during late October and into November when large patches of brown grass become blatantly obvious. The fungus causing brown patch will be active until a lawn goes dormant.
Heavily fertilized and over-watered lawns are very susceptible to brown patch. Lush-growing, moist grass creates an ideal environment for development of this disease. An attractive lawn can be maintained with a balanced fertility program and moderation in watering. And doing so will not only substantially lessen the potential for brown patch development but it will also save money! By the same token, lawns subjected to relatively low maintenance levels seldom have the disease.
Brown patch is strictly a cool weather problem, so do not be confused by brown areas of the lawn that developed during the summer. These were caused primarily by chinch bug damage.
Not only is brown patch unsightly, but weeds more likely to invade the lawn in disease-weakened areas. Also, spring recovery is delayed in areas damaged by brown patch. Fungicides containing bayleton (such as Green Light's Fung-Away and a variety of other labels), chlorothalonil (Daconil 2787), or PCNB (Terraclor) will control brown patch when applied according to label instructions.
For the fungicides to be most effective, it is best to apply them during the early stages of disease occurrence. Even in cases where the disease is in advanced stages, it will be well worth the effort to treat such cases as soon as possible. In lawns to be spot-treated, be sure to also treat the areas that were previously infected since the disease has a tendency to reappear in the same areas.
It's also a good idea to raise the mowing height to 1½ or 2 inches for affected bermuda lawns. The taller grass provides more cover and insulation for the growing points of the grass in addition to reducing overall plant stress and the possibility of winter kill. Raising the mowing height will also provide similar benefits for St. Augustine lawns.
Following these management practices for brown patch will result in a more healthy and vigorous lawn next year.
This web site is maintained by Master Gardener Laura Bellmore, under the direction of William M. Johnson, Ph.D., County Extension Agent-Horticulture & Master Gardener Program Coordinator.
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