Why is the grass orange?
In recent weeks, turfgrass rust has become a problem for Douglas County homeowners. Hopefully we have seen a seasonal end to this colorful infection. However, if you have been wondering why your lawn has an orange, yellow or brown tinge, or why your animals and shoes have been coated with an orange dust, the answer is turfgrass rust.
Rust is a fungal infection that occurs, to some extent, on all turfgrasses. However, there are some susceptible cultivars, including: Kentucky bluegrass, tall fescue and perennial ryegrass. Rust symptoms usually appear in late August to early September and continue through the fall months. From a distance, rust-infected turf can range in color from cinnamon brown to orange or yellow, depending on the species of rust fungus. Cool nights with heavy dew followed by warm sunny days stimulate the development of rust. Moderate temperatures (68 to 85 degrees F) and extended wet periods can also cause this fungus to grow. Outbreaks tend to be more severe in partially shaded areas, such as under trees or along fence rows.
The powdery spores rub off easily on fingers, shoes, clothing and animals. You'll be happy to know that rust is not harmful to either humans or animals. However, it is important to limit traffic on affected grass, as walking through infected areas can spread this disease. If you have walked across an infected lawn, wash spore covered shoes to avoid the spread of the disease. Rust overwinters in infected plants and can be re-introduced each summer by wind-blown spores.
Rust is most easily managed by maintaining a healthy lawn. Don't over or under fertilize. Mow your lawn regularly at higher settings, and remove the grass clippings. If you mow grass that is already infected by rust, clean your lawn mower blades with a 10 percent bleach solution to avoid spreading the spores to non-infected grass. Water your lawn infrequently as the weather cools, and water in the morning so the blades of grass dry quickly in the sun. For long-term disease management, choose grass cultivars with a high level of resistance to rust.
Because the rust epidemic is dependent on weather, chemical management is not recommended. In most years rust does not reach damaging levels before the turfgrass enters winter dormancy, so fungicides are not routinely used for rust control.
For more information about lawn care and disease, contact me at the Douglas County Extension Office at (320) 762-3890.
Hope these glorious autumn days have been fruitful!
Until next time, happy gardening!
"Winter is an etching, spring a watercolor, summer an oil painting and autumn a mosaic of them all."
- Stanley Horowitz