The first hint of a condition called "lawn rust" often comes from the bottom of your shoes, Chris Enroth, University of Illinois Extension horticulture educator, said.
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 said. Many conversations follow this pattern:
'What is it?'
The orange-red tint comes from 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.
'Is it safe to walk on?'
Yes. Rust will not harm humans and is more of a nuisance than anything else.
'How do I get rid of it?'
The easiest solution is to just wait until cooler weather. Once growing conditions become more favorable to cool-season lawn growth, you'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.
'How can I 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 said.
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