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.
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.
Use the Turf Irrigation Management System available on TurfFiles to schedule irrigation based on weather conditions and turf needs. 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.
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.
2 Apply fungicides in 2 to 5 gallons of water per 1,000 square feet according to label directions. Use lower rates for preventive and higher rates for curative applications.
3 Use shorter intervals when conditions are very favorable for disease.
* Products marked with an asterisk are not labeled for home lawn use.
++++ = excellent control when conditions are highly favorable for disease development
+++ = good control when disease pressure is high, excellent control when disease pressure is moderate
++ = good control when disease pressure is moderate, excellent control when disease pressure is low
+ = good control when disease pressure is low
? = not rated due to insufficient data
Low = Rotate to different chemical class after 3-4 applications; tank mixing not necessary
Medium = Rotate to different chemical class after 1-2 applications; tank-mixing with low or medium risk product recommended
High = Rotate to different chemical class after EVERY application; tank-mix with low or medium risk product for EVERY application
? = not rated due to insufficient data
Kentucky bluegrass, tall fescue, St. Augustinegrass, zoysiagrass
Months with symptoms
March to June, September to November
irregular distribution across turf stand
Foliar symptoms location/shape
dieback from leaf tip, blighting of entire leaves, or no distinct leaf symptoms
Foliar symptoms color
yellow or orange
blisters on leaves