Occurrence: Primarily late summer and early fall. However, rust can occur during spring, late fall and throughout the winter months if air
temperatures are moderate.
Leaf lesions beginning as light yellow flecks. The lesions develop into reddish-brown pustules and yellow, red or brown spores. Leaves of the affected plants may turn yellow, beginning at the tips and moving toward the sheaths.
Conditions Favoring Disease Development: Periods of 2 to 3 days of overcast or cloudy weather, air temperatures in the low 70s F and high humidity or frequent, light rain showers, followed by bright sunny weather with air temperatures in the 80s F. Rust is most severe on lawn grass with low nitrogen fertilization.
Reduce the amount of time water sits on the leaf by running sprinklers starting at least 3 hours after sunset and programmed to be completed before sunrise. Applying fertilizer will increase grass growth, aiding in the removal of the existing spores. Removing the clippings when mowing is recommended. Fungicides can be useful (follow label instructions particularly relating to timing and rates).