University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

Rust Appearing on Lawns

July 27, 2000

Orange powder is once again showing up on lawns across northern Illinois. This powder is a fungal disease known as rust, which has been common the past few years about this same time of season. Although it may look bad, the disease is not generally considered a threat to kill a lawn.

Rust is actually one of the easier lawn diseases to identify. It appears as an orange or yellowish-orange powder, which are fungal spores, on grass leaf blades. These spores come off very easily onto shoes and mowing equipment. Rust typically develops on lawns growing very slowly. Overall, lawns may assume a yellow, red, or brown appearance.

One of the key reasons rust often develops is a low amount of nitrogen being available to the lawn. Low amounts of nitrogen and sometimes other nutrients along with low water availability slow down how fast the lawn grows. As the grass slows down, rust develops.

Seasons with excess rain, such as we've seen over the first portion of summer, may have rust outbreaks due to depletion of available nitrogen. Cool nights with heavy dew and light, frequent rainfall add to the ideal conditions for rust to develop. Warm, cloudy, humid weather followed by hot, sunny weather also favors rust development on lawns.

Kentucky bluegrass, perennial ryegrass, and tall fescue are all affected, depending on cultivars. Rust spreads via air, water, shoes, equipment, and sod. Rust may weaken turfgrasses and make them more susceptible to other problems.

Control rust through sound lawn care practices. When rust occurs in late summer, keep in mind improved growth conditions of early fall often get lawns growing more vigorously and the rust fades away. Early September is a key time for fertilization. Check soil phosphorus and potassium levels through soil testing.

If conditions are dry, irrigation is also needed to increase the growth rate of the lawn. Water early in the day so the grass dries quickly. Manage problem thatch. Increase airflow over the site and light penetration by pruning trees and shrubs in the area near the lawn.

Finally, when choosing grass seed or sod, select a blend of several cultivars of the species desired for the site. Resistance to rust can vary according to the race of the disease present. A diverse turf stand helps combat rust and numerous other lawn problems.


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