One of the most common lawn diseases among cool season turfgrasses is brown patch (caused by Rhizoctonia solani). As the name suggests, brown patch is a fungal disease that creates circular patches of dead grass in your lawn.
Because brown patch will quickly spread and destroy entire lawns, it is essential to treat brown patch immediately. In this article, we’ll walk you through the symptoms of brown patch and brown patch fungus treatment, as well as the best fungicide for brown patch disease.
What does brown patch look like?
Identifying brown patch in your lawn is quite easy due to the large patches of dead grass this disease creates. While brown patch symptoms may vary with the soil conditions and type of grass, it generally creates thin, circular patches of brown grass in lawns. The patches may vary in color from brown, tan or yellow.
Pictured above: Brown patch breakouts displaying a yellow color in turfgrass.
Additionally, you may notice a ring of smoky, dark grass surrounding the dead patch of grass. When the leaves are wet or humidity is high, small amounts of gray cottony growth, called mycelium, may be seen growing amongst affected leaves.
In some cases, the center of the patch of turfgrass may grow back, leaving a doughnut-shaped spot on your lawn. Other times, the brown patch spreads so rapidly that it thins and kills grass without ever leaving visible circular patches.
The diameter of these patches greatly varies, ranging from a few inches up to several feet. The best way to diagnose brown patch is by submitting a sample to your local university extension office.
Whichever case you are dealing with, it is crucial to treat the condition immediately to restore the health of your lawn.
What causes brown patch?
Brown patch is most common during long periods of hot, humid weather. NC State Extension states:
“The disease can begin to develop when night temperatures exceed 60°F, but is most severe when low and high temperatures are above 70°F and 90°F, respectively. The turfgrass leaves must be continuously wet for at least 10 to 12 hours for the brown patch fungus to infect. Poor soil drainage, lack of air movement, shade, cloudy weather, dew, over-watering, and watering in late afternoon favor prolonged leaf wetness and increased disease severity.”
Other causes include excessively applied fertilizer with nitrogen content along with deficiencies in phosphorus and potassium.
When does brown patch appear in lawns?
Although large patch (Rhizoctonia solani), a similar turfgrass disease found in warm season grasses, typically appears in warm season lawns (St. Augustine, zoysia, centipede grass) during the spring and fall seasons while cool season grass (tall fescue, ryegrass, bluegrass, bentgrass) is generally affected by brown patch in the late spring and continues throughout the summer.
Bermuda grass is not typically affected as its aggressive growth habits allow for it to recover quickly and spread.
What types of grass does brown patch affect?
Brown patch may appear and spread on a number of grass varieties. Generally, tall fescue, ryegrass, bentgrass and bluegrass are the most common types of lawns to be affected by brown patch with tall fescue in the Southeast being the most common.
Pictured above: A close-up of brown patch disease on a turfgrass leaf blade.
While all types of grass can be affected by brown patch or large patch, the severity of this disease may vary. For instance, tall fescue lawns less than a year old may die instantly, whereas bermuda grass, a warm season turfgrass, recovers quickly due to its fast-growing rate.
As for warm season turfgrasses, you may notice large patch appear on centipede grass, St. Augustine grass and zoysia grass. Centipede grass is the most common warm season turfgrass to be affected by large patch fungus, but all grasses are susceptible to this disease.
How do I treat brown patch?
Cultural Control of Brown Patch
The best way to control brown patch is to prevent it from occurring in the first place. By practicing the following techniques, you can avoid the severe damage that brown patch causes on both cool season and warm season turfgrasses.
- Regularly mow your lawn using the proper mowing height for your turfgrass. Mowing grass too low or too high can leave your lawn susceptible to brown patch, as well as other harmful diseases.
- Avoid applying high rates of nitrogen fertilizer on cool season lawns during the late spring and summer. Similarly, high rates of nitrogen on warm season grasses should be avoided in the late fall and early spring.
- Avoid over-watering your lawn and provide proper drainage at all times. For best results, irrigate your lawn in the mornings for a total of 1 inch of water per week.
- Test your soil and apply the proper fertilizer for your soil type. Be sure your soil has sufficient levels of potassium and calcium, as this prevents brown patch from settling in.
Generally speaking, most big box fertilization programs prescribe too much nitrogen, which can lead to fungus outbreaks. There are two problems with this strategy:
- Lawns need nitrogen—but not in copious amounts. Slow-release nitrogen fertilizers keep too much nitrogen from entering your soil and plants at once. They’ll also feed your lawn over an extended amount of time so that you don’t have to apply fertilizer repetitively.
- It is better to feed your lawn incrementally throughout the growing season (March–November); not just two times a year.
Sod Solutions recommends the Lawnifi® Fertilization Program. Lawnifi gives your lawn what it needs in the form of nano-sized nutrients, exactly when it needs it in the form of easy-to-apply monthly applications from March to November.
It’s important to note that even with the use of an improved fertilizer program, the timely applications of fungicide is still necessary for overall lawn health. If you fertilize your lawn with nitrogen before applying a fungicide and presently have a fungus, that fungus will expand exponentially, which can be disastrous for your lawn.
Chemical Control of Brown Patch
If brown patch has already occurred in your lawn, the next step is finding the proper treatment. Although applying brown patch fungicide can be slightly challenging, it is definitely effective for controlling the disease in your lawn.
What is the best fungicide for brown patch?
When searching for the best disease control for brown patch, there are many options to consider. For best results, you may consider using azoxystrobin, pyraclostrobin or fluoxastrobin for controlling brown patch in your lawn. These fungicides are available in brands such as Heritage G, Pillar G Intrinsic Fungicide and Fame Granular Fungicide. Other fungicides for brown patch treatment include propiconazole, triadimefon and myclobutanil.
How do I prevent brown patch?
While disease control products are generally used for fixing brown patch in your lawn, it may also be used to prevent brown patch from occurring in the first place. Apply one of the products above at a preventive rate during the spring or fall on warm season turfgrass if you’ve had brown patch before. Apply at a preventive rate in the late spring to prevent disease outbreaks in the summer for cool season turf.
Be wary of the disease becoming resistant to applications of the same chemical if you apply disease control multiple times. Consider rotating group 3 (propiconazole) and group 11 (azoxystrobin) fungicides to keep this from happening. Learn more here. Because applications vary with different grass types, it’s important to follow the label’s directions precisely. Generally, fungicide applications take place in 14–28 day intervals, although the time of year for application may differ among cool season and warm season turfgrasses.
Finding an effective brown patch fungus treatment does not have to be a difficult process. By using one of the fungicides mentioned above, you can control and prevent brown patch from appearing in the future.