How to Identify and Control Rust in the Lawn

Have the grass blades on your lawn begun to look like they've been coated with rust? Here's what's going on— and what to do about it.

Unlike the kind of rust you see on your car, which is caused by a chemical reaction, rust diseases on grasses are caused by various species of common lawn fungus. So named because they give grass blades an orange-yellow, rusty appearance, rust diseases affect a wide range of turfgrass species. Use these expert tips to help you figure out if the problem your lawn is experiencing is indeed a rust disease and, if so, what to do about it.

Favorable Conditions for Rust Diseases

Rust diseases are most likely to appear from spring through fall during mild (68 to 86 degrees F), wet weather, although it can also develop during drier periods of bright sun and heat following milder, humid weather. Stressed, undernourished turf is especially susceptible to this disease.

Grass Types Commonly Affected by Rust Diseases

  • Perennial ryegrass
  • Tall fescue
  • Kentucky bluegrass (some varieties) 
  • Zoysiagrass

If you're unsure which type of grass you have, read "Identify Your Grass". Also, when choosing which grass to plant, you will generally get a more disease-tolerant lawn by planting multiple species and varieties.

How to Identify Rust Diseases

Check for irregular, light-yellow patches in the lawn, as well as small, yellow flecks on individual grass blades. These flecks enlarge as the disease progresses, causing a rupture of the blade's surface and the release of yellow-orange, powdery spores that stick to everything from shoes and pant legs to mowers and pets. (Don't worry, grass rust won't harm pets.) When a rust disease outbreak is especially severe, you may also notice thinning turf and die-back of grass blades.

As you walk your lawn, pay special attention to areas that are shaded, have compacted soil, or are newly seeded. The development and spread of rust-causing fungi are made worse in places where there's less vigorous grass, excessive wetness on grass blades, or not enough of the main nutrient (nitrogen) needed for greening and growth.

How to Control Rust Diseases

If you've identified rust as the problem in your lawn, you should take action right away. First, make sure your lawn is well-fed and sufficiently watered. If you don't see any improvement within a couple of weeks, apply a systemic lawn fungus control like ScottsÂŽ DiseaseEX™ Lawn Fungicide. This product starts working in 24 hours to control rust diseases (as well as other diseases listed on the label) and keeps on working for up to 4 weeks. Together with good lawn management practices, a fungicide can help control existing fungal outbreaks and prevent new ones.

How to Repair Lawn Spots Damaged by Rust Diseases

A healthy lawn can help ward off rust diseases, so once the problem is under control, patch any resulting bare spots using ScottsÂŽ EZ SeedÂŽ, which contains high-performance seed, a water-absorbent mulch, and continuous-release lawn food to make sure tender seedlings get everything they need to grow big and strong. For general lawn thinning, use ScottsÂŽ Turf BuilderÂŽ Thick'R Lawn™, which does 3 important things in the same application: seeding and feeding your lawn, plus helping improve the soil. Always follow label directions when seeding, and patch during spring or fall for best results.

How to Maintain a Healthy Lawn

Because stressed, hungry, and improperly irrigated lawns are more susceptible to rust diseases, one of the best ways to help prevent them is to keep your lawn healthy and strong. Here's how.

  • Feed properly. Give your lawn the right amount of nutrients on a regular basis. Proper feeding with ScottsÂŽ Turf BuilderÂŽ Lawn Food not only greens up your grass but also helps roots grow deeper and stronger to better withstand a variety of lawn diseases and insects.
  • Maintain adequate levels of moisture. Not too little and not too much is the key. Water in the morning to prevent prolonged wetness of grass plants. Aerating and dethatching every 1 to 3 years will allow air, water, and nutrients to move more freely into the soil.
  • Mow regularly. Keeping your lawn cut to the proper height for your grass type helps discourage weeds and encourage vigorous grass growth.

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