Treat rust disease on lawn
Q: I recently noticed a couple of sections ofmy lawnthatwere off-color and very stunted in growth. WhenIwalked through these areas, my shoes got covered with what appeared to be an orange powder. What is this problem, and is there something that I should do to improve the lawn?
– Anton Gunderson, Buffalo Grove
A: The description of the problem with your lawn indicates that you have rust, which is a fairly common disease on residential lawns that consist ofKentucky bluegrass and perennial ryegrass.
Rust outbreaks are most common in late summer and early fall, although the disease can occasionally be active in early spring, especially on lawns that have not been fertilized adequately. It is most likely to affect lawns that are starved for nitrogen.
Turf that is infected with rust appears to have a yellow-green cast to it from a distance. The turf is less vigorous in growth than healthy turf nearby, as you are observing in your garden. There can also be a red or brown tint to the affected areas.
As the disease progresses, the symptoms occur in an irregular pattern around the initial site of the infection. Look for numerous small, yelloworange bumps on the grass leaf blades. Walking through grass that has a high level of infectionwill disturb and then release lots of orange spores, leaving an orange color on your shoes. These spores spread the disease to other areas of the lawn.
Rust is generally just a cosmetic issue for established lawns, though the orange spores can be a nuisance by covering shoes, kids, pets and lawn
mowers with a rusty-colored residue.
Rust can severely damage and kill areas of lawn that you have seeded in spring and that lose vigor during hot and dry weather. In these cases, youmay need to overseed the damaged area to restore the turf.
Rust diseases aremost severe on slow-growing turf that is stressed by drought, summer heat, low fertility, shade or compacted soil. Until the recent rains, therewere severalweeks of hot and dryweather that created stress on lawns and left good conditions for rust.
This disease needs moderate temperatures of 50 to 60 degrees Fahrenheit and long evening dew periods to keep the foliage moist. Warm, cloudy, humid weather followed by hot, sunnyweather also promotes rust development.
Maintaining a healthy and vigorous stand of turf is the most effective and efficient method to control and prevent rust in the future. Mowing removes the infected tissues before they become problematic. This is a good time of year to fertilize your lawn. You should also provide supplemental irrigation to reduce drought stress and help the infected areas recover, should dry conditions return later this fall.
Since leafwetness is required for infection, it is important towater early in
the day to allowthe turf to dry before night. Generally, it is best towater the turf infrequently and deeply.
Seasons with excess rain can also have outbreaks of rust due to the depletion of nitrogen in the soil. Should you run into this problem at a different time of year, you can apply additional fertilizer to the problematic areas at a lowrate of 1⁄
5 to ½ pounds of nitrogen per 1,000 square feet to promote leaf growth and allowthe turf to outgrow the rust’s relatively slow infection cycle.
Several fungicides are available and effective against rust in case your cultural practices do not work; however, they are usually notwarranted on established turf. On newly seeded stands, apply fungicides at the first sign of disease if youwant to treat aggressively. In most cases, a single application of an effective fungicide combined with efforts to encourage turf growth, will suppress outbreaks of rust.
Your other option is to simply increasewatering and lightly fertilize the affected area to see if it will growout of the disease.