What Is Grass Rust and How Do I Get Rid of It?

Have you noticed a yellowish-orange patina overtaking your lawn during these late days of summer? It's most likely common grass rust.

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What Is Grass Rust?

Grass rust (Puccinia sp.) is a common visitor to residential lawns beginning in August and persisting through the fall months. It is a fungus that feels right at home when visiting stressed Kentucky bluegrass and perennial ryegrass in the North and tall fescue and zoysiagrass in the mid-South. No need to sweat, it’s generally just a nuisance and causes no serious damage to your lawn.

What Does Grass Rust Look Like?

Grass rust gives your lawn a yellowish-orange to reddish-brown appearance. A bad case of it can make your entire lawn look off-color. Look closely and you’ll see tiny pustules on individual grass leaves. If your white shoes turn orange after walking through your lawn, you have rust. These pustules burst easily, spreading their “rustiness” throughout their surroundings.

You may also notice a general thinning of your grass as the rust becomes more prevalent.

What Causes Grass Rust?

Grass rust is a fungus. Like all plant diseases, when conditions are ripe for activity, it can seem to appear out of nowhere. You’ll see grass rust show up in your lawn in late summer or early fall when the conditions are right.

Lawns will show signs of general stress during this time as they approach the end of a long growing season. Low light, in the form of shade or shorter day lengths, can trigger grass rust activity. Daytime temperatures in the 70s F coupled with high dew points is great grass rust weather. Prolonged periods of cool, wet weather will foster activity, too. But of all the conditions where grass rust is present, a slow-growing lawn deficient of nitrogen and water is the easiest target.

How Do You Get Rid of Grass Rust?

Good news here! Grass rust is probably the easiest lawn disease to get rid of.

An application of a high-nitrogen, quick-release fertilizer, such as Scotts Turf Builder WinterGuard Fall Lawn Food, when rust appears will make it disappear quickly. Nitrogen triggers leaf growth. This surge of growth when the lawn is naturally trying to slow down will grow the grass out of trouble. If your lawn is dry, watering the grass will also stimulate growth. Applying a fungicide is seldom necessary and not recommended.

How Do I Prevent Grass Rust?

You can prevent grass rust from showing up in your lawn simply by keeping it well fed. However, you don’t have to go overboard with fertilizer.

Four timely applications of a nitrogen-based lawn food, such as Scotts 4-Step Program, will keep your lawn green and healthy, enabling it to fend off rust and most lawn diseases. Two applications should come after August 1; plan those around August 1 and Sept. 15. Those dates can vary depending upon where you live.

Proper fertilizing and other lawn care practices, such as proper watering, shade management and core aeration, can keep your lawn healthy enough to resist diseases and other lawn ailments.

Those grass rust pustules appear mostly on the leaf blades. If you bag clippings as you mow, you’ll remove some of the infected leaf tissue, improving your chances of keeping it under control. Just don’t add clippings of rust-infested grass to your compost pile. Also, if you hire out your lawn care, know that commercial mowers can oftentimes spread it from one lawn to the next.

When reseeding your lawn, look for a mix that contains rust-resistant varieties. Because many species and varieties mingle in today’s grass seed mixtures, you may need help here. Refer to your local lawn and garden extension service for help. Retailers who take selling grass seed seriously may be good resources of information, too.

Joe Churchill
Joe Churchill is a Senior Turf Specialist for Reinders, Inc. in Plymouth, MN with a passion to promote realistic and environmentally-sound turfgrass maintenance practices through responsible use of water, fertilizers, pesticides and other inputs. Joe's client base includes professional turf managers serving the lawn care, sports turf and golf course industries. His lawn is the envy of the neighborhood and, in his free time, he enjoys kicking back on the Northshore of Lake Superior.