Recent periods of overcast and wet weather have led to outbreaks of a disease known as “rust” on tall fescue, Kentucky bluegrass, and zoysiagrass. Rust is most severe on slowly growing turf, so under-fertilization and/or drought-stress often contribute to problems with this disease. Rust is of most concern on zoysiagrass. This warm-season turfgrass grows very slowly in the fall and spring due to cool temperatures and short day lengths. This reduction in growth and lack of frequent mowing allow rust to cause thinning in worst-case scenarios.
Early symptoms of rust start out as small yellow flecks on the foliage. These yellow flecks will soon turn into orange pustules/blisters that are raised on the leaf surface. As the disease progresses, irregular areas of turf will turn yellow/orange and begin to thin out. In heavily infested areas you may notice yellow/orange dust clouds when disturbed, i.e. from mowing. These are the spores being released and spread about.
Fungicides are available for preventative and curative control of rust. Treatment will likely only be necessary on zoysiagrass, as cool-season grasses like tall fescue and Kentucky bluegrass will out-grow the disease if they are fertilized sufficiently.
For more information about rust and fungicide programs, please visit the following link: