Lawn rust and why your shoes are turning orange

URBANA, Ill. – The first hint of lawn rust often comes from the bottom of shoes, says Chris Enroth, University of Illinois Extension horticulture educator. Homeowners may notice some slight discoloration of the lawn, but nothing too alarming until they slip off their shoes and notice a reddish-orange color.

"That's when homeowners call the Extension office asking about the strange substance on their shoes after walking through their lawn,” Enroth says. The conversations follows: 

"What is it?" 
The orange-red tint is fungal spores from a group of related fungi that cause lawn disease rust. Kentucky bluegrass and perennial ryegrass are almost exclusively affected. Rust is more often found on lawns with a taller mowing height, yet, it is mostly cosmetic.

Rust favors dry soils and high humidity conditions, including long evening dew periods. “Lawn rust typically develops later in the summer and in early fall when cool-season lawns are growing very slowly,” Enroth explains.

"Is it safe to walk on it?"
"Yes, it is safe to walk on a lawn with rust," Enroth says. Rust will not harm humans and is more of a nuisance than anything else. The fungal spores are easily detached and will cover just about anything that walks or moves over the lawn, including shoes, pets, and mowers.

How do I get rid of it? There are a few ways to reduce or eliminate rust. “The easiest solution is to just wait until cooler weather,” Enroth says. “Once growing conditions become more favorable to cool-season lawn growth, we’ll simply mow off the rust and it will no longer be an issue.”

Homeowners may also encourage lawn growth using fertilizers. Apply 1 pound of nitrogen fertilizer per 1,000 square feet. Rust is common on slow-growing grasses. Nitrogen will stimulate your lawn to grow and surpass rust’s slow disease cycle.

“Applying nitrogen in the late summer to early fall is a good practice and is a recommended part of your cool-season lawn routine,” Enroth says.

How to prevent lawn rust? Avoid irrigating during the evening. Evening watering prolongs the dew period, favoring rust development. Hollow core aerate when lawns are actively growing in the spring or fall. Rust can be more common in compacted soils, so aerating will relieve soil compaction.

There are species of turfgrass that are resistant to rust. Killing off a lawn and reseeding it in rust-resistant turf-type tall fescue is one way to prevent future rust. Tall fescue is a popular pasture grass and, recently, the turf industry has started breeding this species to match common lawn grasses. To keep Kentucky bluegrass lawns rust free, overseed it with new varieties of Kentucky bluegrass that are more resistant to rust.

Because lawn rust is mainly cosmetic, fungicides are only necessary if a homeowner demands a high-quality lawn. “There’s no reason to spray another pesticide in the environment if we really don’t have to,” Enroth says.

University of Illinois Extension is the flagship outreach effort of the University of Illinois at Urbana-Champaign, offering educational programs to residents of all of Illinois' 102 counties and far beyond. Illinois Extension provides practical education you can trust to help people, businesses, and communities solve problems, develop skills, and build a better future. Through our Agriculture and Natural Resources programs, Illinois Extension supports the economic viability and environmental sustainability of natural and managed landscapes and productive lands in Illinois. Horticulture program educators provide research-based information and training about gardening, fruits and vegetables, flowers, insects and diseases, composting, landscaping, and more.

News source/writerChris Enroth, Horticulture Educator, Illinois Extension