Numerous infectious diseases can occur on lawns in Kentucky. Unless diagnosed and managed, these diseases can sometimes cause extensive damage. A sound lawn management program provides benefits in two ways: it reduces the severity of lawn
diseases; and improves the lawn’s recovery should a disease outbreak occur. You can control diseases of turfgrasses most effectively by using as many of the following lawn management practices as feasible.
The first step in improving your lawn is to accurately diagnose the problem. Although diseases are sometimes responsible for poor turf quality, they are not the only cause. You may need to consider some other possible causes of thinning or dead grass: improper fertilization, chemical injury, mower problems, dog or insect injury, localized dry spots, poor soil drainage, excessive thatch, and competition from other plants. Bring samples of diseased turf into the Extension Office for assistance.
Underfertilization makes certain diseases worse, whereas overfertilization worsens others. For greatest lawn health, make sure your program provides moderate fertility. Lawns of Kentucky bluegrass, tall fescue, or perennial ryegrass should receive no more than three to four pounds of total nitrogen per 1,000 square feet each year; even less nitrogen is acceptable for lawns on a low-maintenance or moderatemaintenance program. Most or all of the fertilization should be applied during the fall months, which helps to promote recovery of the grass in the event a summer disease outbreak has already occurred. Avoid heavy applications of fertilizers during spring and summer, as lush spring or summer growth can be more prone to certain diseases. Also, have the soil
tested to determine whether lime, potash, or phosphate should be applied to meet your lawn’s fertility needs.
Mowing too closely during the hot months of summer can stress the lawn, increasing susceptibility to diseases and environmental extremes. Mow lawns at a 2- to 2 1/2-inch height. Mowing too high can also favor some diseases, particularly in the late autumn. Continue mowing through late autumn to prevent leaf tissue from accumulating. A thick covering of leaves on the lawn during the autumn and winter can lead to outbreaks of disease during wet weather even though the grass is dormant.
Keep the mower blades sharp. A dull mower shreds the grass blades. This not only causes
the lawn to be temporarily unsightly, but it may also provide wounds for infectious
fungi to invade.
Avoid frequent, light waterings of your lawn. This encourages the grass to develop a shallow root system and frequently provide the moisture that fungi need to infect the leaves. When watering, saturate the soil to a depth of three to four inches to promote deep rooting. If a disease outbreak is evident, water early in the day so that the leaves dry by nightfall. If the lawn is watered late in the day, the leaves may remain wet until morning, thus providing long periods of leaf wetness favorable for infectious fungi.
Control weeds, insects, and other lawn pests which can cause stress. A stressful
turfgrass environment often favors diseases. Follow all label directions when using lawn
chemicals, as improper application can sometimes lead to turfgrass injury.
Fungicides can be an important part of a disease-control program in an intensively managed turf, such as putting greens on a golf course. However, if you follow a sound program of lawn management through the practices described above, rarely should you need fungicides for a home lawn. Before using any fungicide, be sure the disease is properly diagnosed. If a disease breaks out in your lawn, keep in mind that a return to weather favorable for turf growth and vigor will help alleviate the problem.
Submitted by Adam Leonberger, Agent for Horticulture, Franklin Co. Cooperative Extension Service