If you had brown patch circles last fall, you will most assuredly have them again this year.
Brown patch, a fungal disease caused by Rhizoctonia solani, presents a serious threat to most turf grasses each autumn. This is one of those “good news, bad news” situations. The good news: It’s not life-threatening. The bad news: If you don’t catch it early, it will make your lawn ugly October through December.
With wetter conditions and slightly cooler fall temperatures (insert joke here about “cool” Houston weather), brown patch can be a challenge for many homeowners. As we head toward a temperature range I call the “80-60 split,” we have to be really mindful of this disease, and forecasts for the coming two weeks are calling for daytime highs in the 80s and overnight lows in the 60s. That’s when brown patch starts to spread.
In warm-season grasses, the disease is characterized by at least two symptoms. The most common is a circular pattern of brown grass with a yellowish ring (a “smoke ring”) of wilted grass at the perimeter. The leaves can be easily pulled from the stolons within the ring because the fungus destroys the tissue at the base of the leaf sheaths. Symptoms first appear as small circular patches of water-soaked, dark grass that soon wilt and turn light brown. Stolons often remain green. As the disease develops, the circular patches enlarge, the rings become more apparent, and new green leaves may emerge in the center of the circular areas. Fungal activity generally stops when air temperatures reach 90 F.
High levels of nitrogen may increase the severity of the disease, so products touted as “fall fertilizers” that are very high in nitrogen can make it worse. Those fertilizers, however, are almost always national brands, not those recommended on GardenLine.
With cool-season grasses, the disease first appears as dark green, water-soaked circular patches that range from a few inches to several feet in diameter. The affected leaves wilt and turn light brown, but remain upright. A dark, grayish-black ring of wilted grass often is present around the perimeter of the diseased areas in the early morning.
Now let’s talk about control. First, remember the severity of the disease can be managed to some extent by avoiding heavy applications of nitrogen during spring and fall. Water early in the morning to remove dew and allow the grass to dry quickly. And, when possible, remove grass clippings during periods of disease activity.
To prevent it in the first place, start with one of the preventive controls listed below NOW, and do it again in 30 days. If you see circles pop up, also include a curative control on and around the circles. If you’ve already got brown patch, the use both a preventative control and a curative control NOW … followed by another curative in 30 days and another after 60 days.
- Terrachlor (Granular)
- Pentachloronitrobenzene (PCNB) turf fungicides (Terrachlor-based granules)
- Systemic bayleton (Granular and liquid, but hard to find)
- Bonide Image or Fertilome Liquid Systemic (PCNBs also known as Banner-based liquids)
- Benomyl (Granular or wettable powder, also hard to find)
Curative/Topical Controls (to halt disease):
- Myclobutanil (Such as F-Stop from Fertilome)
- Fertilome liquid systemic or Bonide Image
- Consan 20 (Must be used once a week)
- Maneb (If you can find it)
- Terrachlor (Any liquid or granular form, but you may have to double the dose as a curative)
- Leaf mold compost (Vegetative compost – the ultimate organic control)
- Liquid garlic sprays