What is going on with lawn grasses this year?

We have had several calls about thin patches in the lawn or browning areas.  Our weather this year has not been typical for the season.  Many cloudy days, extra rainfall and high humidity, and a slower warm up have all contributed to some challenges.

Brown patch is a disease that commonly shows up on cool season turfgrasses, especially Tall Fescue, but can occasionally appear on hybrid bermudagrass and zoysiagrass. Brown patch disease appears as brown patches up to three feet in diameter. Leaves first take on a dark color, then wilt and turn brown.

Brown patch usually occurs in hot, humid weather when night temperatures are above 60°F and foliage remains wet for prolonged periods. Poor soil drainage, lack of air movement, cloudy weather, heavy dew, overwatering and watering in late afternoon favor prolonged leaf wetness and increased disease severity. The application of high rates of nitrogen and or deficiencies of phosphorus and potassium, especially when weather conditions are favorable for brown patch, can increase disease severity. Excessive thatch, mowing when wet and leaf fraying by dull mower blades can also enhance the severity of brown patch.

Control. Control starts with good management practices. Though there are varieties of turf-type Tall Fescue that are considered resistant to brown patch, even resistant varieties succumb when growing conditions are less than ideal for growth of strong plants (as described above) and environmental conditions are highly favorable for disease development.

When environmental conditions favor disease, avoid application of excessive rates of nitrogen. Fertilizer should be applied judiciously, and adequate amounts of phosphorus and potassium are essential to ensure the highest possible levels of plant resistance. In general, cool-season turfgrasses should not receive more than one pound of actual nitrogen per 1,000 square feet at any one time. Use very low rates or avoid applying nitrogen in late spring or summer to cool-season turfgrasses. In a typical home lawn situation, the last application of fertilizer in the spring should be applied no later than early May. Remember, I am talking fescue here.  Ensure adequate amounts of phosphorus and potassium by applying these nutrients based on soil test results.

Reduce prolonged leaf wetness by watering infrequently to a depth of 6 to 8 inches and at a time when the foliage is likely to dry quickly. Avoid watering in late afternoon and evening, and allow for better air movement by removing unwanted vegetation and selectively pruning trees and shrubs. Good surface and soil drainage must be present to reduce disease incidence.

Make sure mower blades are sharp to reduce the amount of wounded turfgrass in which the fungus can enter the plant. Collect and promptly dispose of clippings on infected areas or when conditions favor disease development. Avoid mowing turfgrass when wet, and do not mow too low so that the turfgrass will be better able to resist the disease.

Applications of effective fungicides, when the first disease symptoms appear, will give good control of brown patch on highly maintained turfgrass. A preventative fungicide program should be considered in areas where the above conditions are difficult to control or change and when conditions are favorable for disease development.