Use cultural controls to fight lawn rust
Here at the UI Extension office, we use many techniques to look for signs of plant diseases.
We poke and prod, magnify and macerate. We place speckled leaves in a moist chamber (plastic bag with a moist paper towel) and wait for fungal spots to show their spores.
With one disease, the technique is simple — just a stroll across the lawn. With each of your steps, your lovely shoes develop orange tips. Yes, you and your shoes have been dusted with fungal spores. But there is no need to spurn these spores. This is one disease that can be managed with cultural controls.
Turf rusts generally appear when our weather shifts from cool and moist to hot and dry. Lawn rust is typically seen in late summer to early fall when the weather is dry. If fungal lawn rusts appeared in the crop report, we would declare a bumper crop this year.
Early symptoms of lawn rust disease include light yellow flecks or spots on grass leaves and stems, giving the lawn a yellow appearance. Eventually, the leaf tissue ruptures at these yellow spots, and yellow, orange, brown or red spores of the fungus are produced.
The spores rub off very easily to bespeckle and bedazzle your hands, shoes, clothing and animals. Often, the disease goes unnoticed until you mow the lawn or your dog walks across your white carpet.
All turf grasses can be infected with rust fungi, but Kentucky bluegrass, perennial ryegrass, tall fescue and zoysiagrass tend to be most susceptible, depending on cultivars. Rust spreads via air, water, shoes, equipment and sod. Although lawn rust is largely cosmetic, it may thin and weaken turf grasses and make them more susceptible to other problems.
Rust typically develops on lawns growing very slowly and in areas of the landscape with poor air circulation. Depending on the weather, pretty much anything that makes the grass grow slowly can favor rust disease. This year, low water availability has slowed turf growth, allowing rust to develop.
As grass grows, the rust-infected leaves are pushed upward, making it easy to mow and remove infected blades. Collecting and removing clippings can help lessen disease. Mow regularly to remove infected leaf tips, but avoid mowing below 2 inches for most lawns. Prune surrounding trees and shrubs to improve light penetration and air circulation around densely shaded areas. Water early in the day so grass dries quickly. Aerate to manage thatch and soil compaction. Increase lawn vigor with an early September nitrogen application, but don't overdo it. Check soil phosphorus and potassium levels through soil testing.
When rust occurs in late summer, a laissez-faire attitude may be best as cooler wetter weather typical of early fall usually gets lawns growing more vigorously and the rust fades away. If conditions are dry, irrigation can help to increase the growth rate of the grass.
Fungicides are rarely suggested on home lawns for rust control. Focus on cultural practices described above. If the lawn is badly infected or the combination of rust and other stress produces a poor lawn, it may be time for a lawn intervention renovation, ideally done in mid- to late August.
Use a blend of turf cultivars with resistance to rust as listed in UI Report on Plant Diseases No. 412, http://ipm.illinois.edu/diseases/rpds/412.pdf.
Begin by choosing a quality turf grass seed blend of several cultivars of the species desired for the site. A diverse turf stand helps combat rust and numerous other turf problems.
Lessen the incidence of rust through sound lawn management. If you are not sure what sound lawn management is, check out http://urbanext.illinois.edu/lawntalk/ or give us a call at 333-7672 in Champaign, 815-268-4051 in Onarga or 442-8615 in Danville.
Sandra Mason is unit educator, horticulture and environment, for the UI Extension, Champaign County. Contact her with questions or comments at 801 N. Country Fair Drive, Champaign, IL 61821, call 333-7672, email firstname.lastname@example.org or fax 333-7683.