Causal Agent: Rhizoctonia solani
All species of warm- and cool-season turfgrass.
The symptoms of brown patch can vary depending on the grass cultivar, climatic and atmospheric conditions, soil and intensity of the turfgrass management. This disease typically causes rings or patches of blighted turfgrass that measure between 12 cm and 3 m in diameter. It also causes leaf spots and "smoke rings"-thin, brown borders around the diseased patches that appear most frequently in the early morning.
After the leaves die in the blighted area, new leaves can emerge from the surviving crowns. On wide-bladed species, leaf lesions develop with tan centers and dark brown to black margins.
Conditions favouring disease
Brown patch favours high relative humidity as well as temperatures of over 30°C during the day and over 15°C at night. This disease can be quite active at cool temperatures on warm-season grasses in the spring and autumn as temperatures in the turfgrass canopy, which is where infection starts, can often exceed air temperatures.
It also occurs in areas that experience more than 10 hours a day of foliar wetness for several consecutive days. Brown patch infestation is more severe when the turf is cut to a height less than the optimum for that turfgrass species.
Integrated turf management
Use low to moderate amounts of nitrogen, moderate amounts of phosphorous, and moderate to high amounts of potash.
Avoid nitrogen applications when the disease is active.
Increase the height of cut.
Increase the air circulation.
Minimise the amount of shade.
Irrigate turf early in the day.
Improve soil drainage.
Remove dew from turf early in the day.
For best results, use contact or penetrant fungicides to prevent brown patch.