If you had brown patch circles last fall, you will most assuredly get them again this fall. Brown patch, a fungal disease caused by Rhizoctonia solani, presents a serious threat to most turf grasses each autumn. With the onset of slightly cooler temperatures (insert joke here about "cool" Houston weather) and fall's wet conditions, brown patch can be a challenge for most homeowners.
Conditions most favorable for brown patch development include (1) the presence of active fungi, (2) vigorous growth of a susceptible grass, (3) daytime temperature ranging between 75 and 85 F, (4) the presence of free moisture on the foliage, and (5) night temperatures below 68 F.
Symptoms - On warm-season turf grasses, the disease is characterized by at least two different types of symptoms. The most common is a circular pattern of brown grass with a yellowish colored ring ("smoke ring") of wilted grass at the perimeter of the diseased area. The leaves can be easily pulled from the stolons within the "smoke ring" because the fungus destroys the tissue at the base of the leaf sheath. 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, "smoke rings" become more apparent and new green leaves may emerge in the center of the circular areas.
High levels of nitrogen may increase the severity of the disease. Fungal activity generally stops when air temperatures reach 90 F.
On 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 (smoke ring) of wilted grass often is present around the perimeter of the diseased areas in the early morning.
Control - The severity of the disease can be controlled to some extent by avoiding heavy applications of nitrogen during spring and fall, by watering early in the morning to remove dew and allow the grass to dry quickly and, where possible, by removing grass clippings during periods of disease activity.
The following are the recommended controls for brown patch that you'll hear me rattle off time and time again.
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 and when 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 in 60 days.
- Terrachlor (Granular)
- PCMB turf fungicides (Terrachlor-based granules)
- Safe-T Green (granular)
- Systemic bayleton (granular and liquid)
- Fertilome Liquid Systemic (Banner-based liquid)
- Benomyl (granular or wettable powder)
- Bayleton (normally found adjacent to Greenlight in stores)
- Curative/Topical Controls to Halt Disease:
- Myclobutanil (such as F-Stop from Fertilome)
- Fertilome liquid systemic
- Safe-T Green
- Concan Triple Action 20
- Terrachlor (double the dose as a curative)