What is rust?

Rusts are considered a minor disease on turf grass in North America. Most cool season grasses are susceptible to rust. Perennial ryegrass is the most susceptible and Kentucky Bluegrass is slightly less susceptible. Nitrogen deficient lawns are also highly susceptible.

Rusts generally appear on lawns in late summer and fall. The disease is most active during conditions of low light intensity and temperatures between 22-25ºC with high humidity. It appears when the grass is growing slowly or not at all. After infection the symptoms and the stress caused to the turf is enhanced with temperatures between 26-35ºC. Alternating weather patterns with changes from cool wet weather to hot dry weather can also create suitable conditions for the disease.

Rusts survive on living and dead leaf tissue and in the thatch layer of turf grass. Only when weather conditions become suitable do they begin to cause a concern on the lawn. The disease also tends to be more severe in shaded areas.

How can I tell if I have rust?

Initially rust symptoms appear as light yellow flecks on the leaves and sheaths of the grass plants. The spots soon enlarge to form round pustules that rupture to release the powdery spores. Reddish orange spores then develop in large numbers on the leaves of the grass plants. The spores easily rub off on shoes, clothing, animals, mowing equipment or other objects that pass through the infected areas. The spores can also be moved by wind or rain. In most cases the spores only attack the leaf blades causing some wilting and thinning of the grass but don't usually cause permanent damage. As conditions improve and cultural practices alter the grass is normally able to recover. Severe cases of rust can significantly damage turf grass if ideal conditions persist for a long period of time.

If you are not sure if you have Rust in your lawn, contact your local Weed Man Professional for a free healthy lawn analysis. They will determine if you have rust and the best treatment option for your lawn.

How can I treat rust disease?

Rust is considered a minor disease and usually does not cause permanent damage to the turf unless favourable conditions continue for an extended period of time. Several cultural practices will help control rust on lawns by improving conditions in which the disease thrives. As the conditions improve, the disease symptoms will clear up on their own. These beneficial cultural practices include:

  • Provide proper fertility- Nitrogen deficient turf grasses are more susceptible to rust. Regular applications of Weed Man's specially formulated slow release granular fertilizer will help provide your lawn with adequate nutrients.

  • Increase mowing frequency. This will help stimulate turf growth. If you can keep the lawn growing vigourously, it will be mowed before spores can be produced on the grass blades.

  • Collect and dispose of infected clippings where possible.

  • Water lawns deeply and infrequently during periods of drought to keep them growing.

  • Water in the early morning so the lawn will dry out and not have water remaining on the leaf surface for long periods of time, which increases the chances of infection by rust.

  • Have lawn core aeration[link] done to improve drainage and encourage air circulation.

  • Over seed severely rust infected areas with a mixture of grass seed that contains cultivars less susceptible to rust.

  • Thin out shaded areas- this will allow dew and other moisture to evaporate more readily.

If you have any further questions about rust in your lawn or have any other questions or concerns, please feel free to contact your local Weed Man Professional.