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October 15, 2012

Here is a mystery problem from two of our sports turf students, Joel Rieker and Kevin Hansen.  It is from a new Kentucky bluegrass grow-in on one of the new sand-based sports fields on campus.  It is showing up as patches from one to two feet in diameter.  Notice the close up of the turf in the third picture, showing a redish to purple discoloration on new growth.

I am suspecting a nutritional problem.  My guess is phosphorus and I am recommending a application of phosphorus as soon as possible.  I think that there is probably some fungal organism involved but I suspect that it is because the grass is deficient in phosphorus.  We may also try some chlorothalonil fungicide on a test area.  They will also do a soil test on the area and take a sample of the grass to the plant disease lab, but both will take some time.  It is the end of the season and we do need to act fast.

I could be wrong and I would like some feedback on this.  Has anyone seen this before on a bluegrass grow-in on sand?  If so what did you do about it.  Send the response to my e-mail, or put it on the comment section below.  Any ideas would be helpful.

Kentucky Bluegrass Mystery Problem

Kentucky Bluegrass Mystery Problem



September 24, 2012

Here are some pictures of rust disease on Kentucky bluegrass submitted by Damian Richardson, Landscape and Conservation Specialist from Alden, IA.  Rust is caused by fungi in the genus Puccinea.  It is common on Kentucky bluegrass and other grass species in Iowa, but there has not been a lot of it so far this year.  It usually begins to show up about the first of August.  This is the first report of it that I have received this year.  This one was on September 20.  These are some good closeups of the rust pustules on the individual blades of grass.  Thanks for submitting them Damian.

While there are several fungicides that will control rust, I usually do not recommend chemical treatment unless it is on a critical area.  It is usually a sign of relatively low nitrogen.  Just add a little nitrogen and mow regularly and the problem should run its course and disappear.  Some cultivars of Kentucky bluegrass are more susceptible that others.  If it is a continuous problem each year, you may want to kill the existing cultivars with Roundup and replace them with more tolerant varieties.  For information on which varieties show tolerance of rust, see the National Turfgrass Evaluation (NTEP) web site at  (  They have data over several years on rust infestation of many cultivars of Kentucky bluegrass.

If anyone else is seeing a lot of rust, let me know.



July 26, 2011

Yesterday, July 25, I began to notice a lot of damaged grass around campus and around Ames. This was not unexpected because of the extreme weather that we have had lately. We are nearing records for days over 90 F, followed by 70+ F nights with sufficient moisture to keep the turf green. This is ideal conditions for several diseases.

The problem appears to be Leaf Spot caused by the fungal organism (Drechslera poae). The old genus name for this organism was Helmintosporium, a name that still in use by much of the industry. This disease is common at this time of year, particularly when the spring has been wet.

So, if you have this problem, what should you do. There are a number of fungicides labeled for this disease, but usually we let it run its course. The area should recover later in the season and through the fall. Notice in the last picture that the new leaves are emerging in a healthy condition. I am expecting full recovery by September.

The first three pictures below shows leaf spot on central campus at Iowa State. It has now gone into the crown and root stage and the damage is quite apparent.

Damage just outside of Horticulture Building.

Beardshear hall just off of central campus.

Individual leaf showing lesions.

It is typical of this disease to damage older tissue first. Notice that the newly emerging leaves are health.

Here is an additional picture that I took yesterday afternoon on my own lawn.
In the area where afternoon shade cools the Kentucky bluegrass, there is very little leaf spot. In the area that gets the stress from the afternoon sun, there is considerable damage from leaf spot.