On July 17, I received an e-mail from Larry Ginger of American Lawn Care with a picture of rust disease showing up on perennial ryegrass, but not on Kentucky bluegrass. Rust is a fungal disease caused by fungi in the genus Puccinea.
Picture from Larry Ginger showing rust on ryegrass patch in lawn taken July 17.
I had not seen this problem at that time, but yesterday (July 21) I took data on the National Turfgrass Evaluation Program (NTEP) trial at the research station. I found that many of the cultivars were covered with rust. I took data on the rust problem this morning (July 22). I have not seen the problem on the Kentucky bluegrasses as of today, but it clearly a severe outbreak on some of the perennial ryegrasses. Rust often shows up in August on Kentucky bluegrass, perennial ryegrass, and even on tall fesuce (see earlier blogs). This year it is early and appears to be hitting the ryegrasses first.
Close up of rust on Kentucky bluegrass from last year.
Rust spores on my shoes after taking data.
Three pictures of individual ryegrass plots covered with rust on July 22.
Rust is clearly cultivar specific and there were cultivars covered with it and adjacent plots that were completely free of the disease. This is another reason for choosing your grass seed carefully. There is usually a good reason to spend a little more on grass seed. I have not analyzed the data on which cultivars were affected, but that will be in next year's report. NTEP does have data available on ryegrass susceptibility to this disease at ntep.org.
Rust is a fungi and there are fungicides that control it, but we generally recommend that you let the disease run its course. It usually goes away by itself. You may want to treat on sensitive areas, such as sports fields if it becomes necessary.
These plots will be on the tour at the turfgrass field day this Thursday, July 24.