Rust on Turfgrass

Rust is a fungal disease caused by several species of Puccinia.  All turfgrass species are susceptible to rust.  However, it is most commonly seen on Kentucky bluegrass and perennial ryegrass. 

From a distance, rust infected turf has a yellowish orange color.  Close examination of rust-infected grass blades reveals numerous yellow-orange pustules.  Rust can be easily diagnosed by walking across the lawn.  As you walk across the lawn, the bright orange spores of the rust fungi rub off onto your shoes. 

Rust most often occurs in mid- to late summer.  Slowly growing grass is most susceptible to rust infections.  Poor turf growth may be due to drought, high temperatures, low fertility, or a low mowing height.  Warm days, moderate night temperatures, high humidity, and heavy dews provide favorable conditions for rust infections. 

Rust is annoying, but it rarely kills established lawns.  The damage is mainly cosmetic.  Rust can cause serious damage to new, spring-seeded lawns. 

Rust usually fades away when the grass begins growing more rapidly with favorable weather conditions and good cultural practices.  Gardeners can promote turfgrass vigor by fertilizing in September and watering deeply once a week during dry periods.  Water in the morning.  Morning irrigation allows the grass blades to quickly dry, thereby discouraging rust infections.  Mow the lawn on a regular basis.  Rust fungi have a relatively slow infection cycle.  Regular mowing of vigorously growing turf doesn’t allow the rust fungi to complete their life cycle and produce spores.  In most situations, fungicide applications are not necessary. 

When establishing a lawn from seed, select a high quality seed mix.  Inexpensive, poor quality seed mixes often contain grass cultivars that are highly susceptible to rust.