Overview

Early symptoms include small, yellow flecks that develop on the leaves and stems. The flecks expand over time into raised pustules, yellow or orange in color, that rupture to release powdery masses of spores. Infected plants become yellow and are more susceptible to environmental stress. Heavily infected areas become thin and exhibit clouds of orange dust (rust spores) when the foliage is disturbed. The rust pustules on infected leaves turn black during the fall in preparation for overwintering.

Rust fungi survive the winter in living plant tissue from which new spores are produced in the spring. Spores produced in the spring, summer, and fall are spread by the wind, germinate on the leaves, and infect new tissue. Extended periods of leaf wetness are required for the spores to germinate and for the disease to develop rapidly. Rust diseases are most severe in turf that is growing slowly due to adverse weather conditions or inadequate management. Low light intensity, inadequate fertilization, drought stress, and infrequent mowing encourage rust development.

Cultural Control

Plant rust-resistant turfgrass varieties whenever possible to reduce injury from this disease. Select cultivars based on regional trials and university recommendations. When planting cool-season turfs, use blends and mixtures of multiple species and/or varieties whenever possible. Plant shade tolerant grasses and raise mowing heights in heavily shaded areas.

Prune trees and remove unwanted undergrowth to improve air movement and reduce prolonged leaf wetness. Mow the turf on a regular basis, removing no more than 1/3 of the foliage in one mowing. Collect and dispose of clippings taken from infected areas to slow the spread of rust.

Fertilize to meet the nutritional needs of the turf. Submit a soil sample for analysis on a regular basis and apply recommended amounts of phosphorus, potassium, and lime. Apply nitrogen based on university recommendations.

Water deeply but infrequently to encourage deep rooting and reduce drought stress and extended periods of leaf wetness. Avoid watering the turf before sunset or after sunrise.

Chemical Control

Fungicides can be used on a preventative or curative basis for rust control. Susceptible turfs should be monitored regularly for rust development during periods of cool and cloudy weather.

Fungicides are often available in different formulations. Most of the time they are formulated to be applied through a sprayer, however there are some granular versions available that are applied through a rotary spreader. When in doubt, you can hire a landscape professional to make these applications because they are licensed and trained on how to best apply these products.