Over the past 1-2 weeks we’ve been seeing a lot of rust in lawn height turf. At Rocky Ford we are finding it in mainly perennial ryegrass but in little pockets in some newly-established zoysiagrass too.
The rust spores need wet leaf surfaces to infect, and we have definitely had some moist, dewy days and even some very foggy mornings. Though the fungus itself spreads best during wet weather, plants that have been stressed by drought are more susceptible. Nutrient-deficient turf is also more susceptible.
We have some information about rust in our publication Rust Diseases in Turfgrass (pdf).