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RUST DISEASE ON PERENNIAL RYEGRASS

July 22, 2014

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.

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ANOTHER GRAY LEAF SPOT WARNING

September 4, 2012

A year ago, on August 31, 2011, I put up a post warning about Gray Leaf Spot on perennial ryegrass.  This disease shows up rather infrequently in Iowa, but it does occur around Labor Day on years when temperatures are unusually high.  Last year's Labor Day temperatures were in the 90's and if you check the post from September 19, 2011, you will see that it did occur on several golf courses with perennial ryegrass fairways.

This disease is caused by the fungi Pyricularia grisea. It seems to selectively hit perennial ryegrass on intensely managed areas such as golf course fairways and sports fields. Under the right conditions, it can be more devastating than Pythium blight. When it hits, it can wipe out large areas of turf overnight.  Fungicides, such as Banner/Daconil will control it, but they must be applied before the outbreak.  Once the disease begins, it is too late to apply.

The reason I bring this up is that we are in the same weather pattern again this year.  The disease does not always occur when its hot around Labor Day, but it did last year and I would watch for it this year.

The pictures below were taken in 1998 on Willow Creek Golf Course in Des Moines and last year on Cedar Poine golf course in Boone. The dead grass is perennial rye and living grass is Kentucky bluegrass.

If anyone has an outbreak of Gray Leaf Sport this year, let me know and send some pictures. 

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