You're walking through your lawn. You notice some discoloration in patches, but it doesn't seem too alarming. After walking in your front door you begin to slip off your shoes and notice they've been turned an orange-red color. You'd swear it looked like your shoes were rusted-over.

This above scenario is where it typically starts. Homeowners call the Extension office with a strange substance on their shoes after walking through their lawn. Following are the questions that come up in these conversations in their usual order.

What is it?

The orange-red tint to your shoes and lawn are the fungal spores from several related fungi which cause the lawn disease rust. Kentucky bluegrass and perennial rye grass are almost exclusively affected. Rust is more often found on lawns with a taller mowing height, yet it is mostly cosmetic.

Rust typically occurs in the late summer to early fall months. The disease is favored by dry soils and high humidity conditions, including long evening dew periods.

Is it safe to walk on my lawn?

Yes, it is safe to walk on your lawn. 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 things you can do reduce or eliminate rust from your lawn.

Rehab your Kentucky bluegrass lawn into a tall fescue lawn. Kill off your lawn and reseed in turf-type tall fescue. Tall fescue is resistant to rust. If you like your Kentucky bluegrass then overseed cultivars that are more resistant to rust.

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-early to early fall should be a part of your cool season lawn routine.

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 on compacted soils. Aerating will relieve soil compaction.

Because lawn rust is mainly cosmetic, fungicides are only necessary if the homeowner demands a high quality lawn. DMI and QoI (strobilurin) fungicides are very effective against rust. (Purdue Extension)

Additional Resources

https://www.extension.purdue.edu/extmedia/bp/bp-110-w.pdf

http://extension.illinois.edu/lawntalk/weeds/rust_diseases_in_home_lawns.cfm