Master gardener: Rust seen on late-summer lawns

Rust disease fungal spores often appear on grass in late summer and give a reddish-orange cast to the blades.
Rust disease fungal spores often appear on grass in late summer and give a reddish-orange cast to the blades." Photo credit: Julie Moore

If your shoes seem to develop a reddish cast to them when you walk through your yard, you can bet that rust disease has settled on the grass. This powdery fungus is common on late summer and early fall lawns.

The fungus flourishes in the growing conditions of this summer. Until late July, it had been a wet year, which can deplete the available nitrogen in the soil. This August, water became less prevalent, and the grass grew more slowly. These conditions, combined with cool nights with heavy dew, increase the likelihood of a rust outbreak.

When rust disease is heavy in your lawn, it is easy to see a red, orange or yellow cast on the grass blades. These are small round bumps of fungal spores that rub off on your hand or shoes, even your pet’s fur as they move through the lawn. The spores are how the fungus spreads, so human movement, lawn mowers, and the wind and rain cause the disease to move throughout the yard.

Get ahead of rust in the lawn with improved lawn care management techniques. For homeowners who water their lawns, always water early in the day, instead of at night, to allow grass blades to dry. Turf fungal diseases flourish on wet grass blades.

Try to improve airflow around the turf and the amount of light it receives by pruning shrubs and trees that border it.

When mowing, catch the clippings to remove the infected grass blade tops.

Should you need to do reseeding, choose grass varieties that are rust resistant. These varieties can be found on the University of Illinois Extension horticulture website. Also check seed packaging.

A light application of actual nitrogen in early fall can improve the lawn’s vigor and help the lawn to get growing again. Apply a quarter pound per 1,000 square feet of turf. Water this in immediately and rust can disappear without the use of a fungicide. Check soil phosphorus and potassium levels through soil testing.

Email your home garden and lawn questions to uiemg-dupage@illinois.edu or call the Master Gardener Helpline at 630-955-1123. Visit our website at http://web.extension.illinois.edu/dkk/.

Julie Moore has been a master gardener volunteer with the University of Illinois Extension in DuPage County for 10 years and has a degree in ornamental horticulture from the University of Illinois.

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