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Sclerotium rolfsii Spotted at the ISU Horticulture Research Station

July 25, 2013

This spring, as you all know, brought large amounts of rainfall to central Iowa. This was a blessing for most including us the Horticulture Research Station. The water level in the pond returned to its maximum height, soil moisture reached great depths, and reduced the amount water needed to irrigate. The record breaking rainfalls also encouraged moss growth on one of our putting greens. Over the years, we have tried to encourage this growth to continue research on moss controls.

A couple of weeks ago, I noticed spots on the green that appeared to look like dollar spot, however, the spots were only covering the moss and not the bentgrass. I decided to leave the area untreated to see if these spots would continue to spread or remain localized. Within a few short weeks, the disease spread like wildfire across the moss. A sample was taken to the Disease Diagnostic Clinic here at Iowa State University. The pathogen was identified as Sclerotium rolfsii.


Sclerotium rolfsii is a fungal disease that has an extensive host range that targets over 500 species. It is very common in the tropics, subtropics, and other warm temperature regions. However, it is very rare to see the disease this far north. The pathogen rarely occurs when winter temperatures fall below 32˚F. The disease survives in the form of sclerotia. These sclerotia are easily spread by foot traffic and mowing equipment. Most of the research articles that I have read state that control is relatively difficult to achieve. We will continue to monitor the area and post any updates on the control.



July 10, 2013

These are pictures of Summer Patch on Kentucky bluegrass at the Horticulture Research Station.  It is caused by the fungi Magnaporthe poae.  It typically shows up in early summer, particularly in years like this that are very wet early followed by a quick drying period and hot temperatures.  This showed up over the 4th of July (right on time).

The blighted areas with a green center that are surrounded by a circle of dead grass are known as “frog-eyes” and are typical of a number of patch diseases.  It is believed that the organism begins as a saprophyte (organism that feeds on dead plant material) in the middle and moves outward in a circle without damaging living grass.  It only attacks living grass if conditions are right and it reaches a certain level of virulence. The patches here are 10 to 12 inches in diameter, which is common for this disease.

There are several systemic fungicides labeled for this disease, but the trick is to get them down before the symptoms develop.  Contact fungicides will not work.  To treat now would do no good and the symptoms will like last through the summer.  This is a disease for which good records are a must.  On this area, I would need to apply a systemic fungicide in late June next year before symptoms develop.  Core aeration in the fall and irrigation during the stress period of early summer can also help prevent its development.




June 4, 2013

The wet weather has resulted in an increase in slime mold showing up on lawns.  This problem is caused by primitive fungi that exist primarily as saprophytes (organisms that live on dead organic material) and use living grass plants for support.  Fungi in the genera Muctlaga and Physarium are usually the causal agents.  They can take on a wide variety forms.  Sometimes people describe it as something that looks like the dog threw up on the lawn.  Other times it looks like gray slime on the leaves.  Then, it can take on some truly strange appearances that you would not associate with a fungi.

The fungi can be washed off with a hose.  It will usually go away after the wet dreary weather changes.   We generally do not recommend fungicides for this problem.

Larry Ginger of American Lawn Care sent in the first picture earlier this week.  This is typical of the way slime molds generally appear in wet weather.

Slime Mold

 Here is a close up of some slime mold from the research station.


Here is one from my own lawn that looks like the dog threw up.



Here is the most unusual one that I have seen.  This came from a lawn in Iowa.




March 29, 2013

Now that the snow is mostly gone, we are seeing some common early spring problems in lawns.  Here are a couple of things that I observed in my own lawn yesterday.

The first is Gray Snow Mold, caused by fungal organism (Typhula incarnata).  This is a common problems that develops in lawns at this time of year.

 Here is how I know what it is.  The brown fruiting bodies on the tissue are "sclerotia", which are commonly associated with this disease on turf.

 The second problem is a feeding trail of voles that were active under the snow.

Feeding Trails

 Here is the culprit (Picture from Timothy Christians)

There will likely be several turf problems showing up in the next few weeks.   I would appreciate any picture that you have for the blog.



March 20, 2013

It's time to get the blog going again for the spring.  If anyone out there would like to submit something, let me know.

The following blog post is from Tim Christians, Superintendent of Makray Memorial Golf Club,in Barrington, Il.

From Tim Christians:

Diagnosing Tree Defects

Posted on March 13, 2013 by makraygolfmaintenance


Today while removing trees that had been affected by Imprelis Herbicide, I came upon an Ash tree that showed significant internal defects. I was able to determine this by the presence of fruiting bodies on the tree.

There are many reasons for a tree to begin to decay. In the situation of the tree found today it was due to poor trimming techniques that left the tree prone to attack by insects and other pathogens.

The fruiting bodies present on the tree are only a sign of what truly is happening inside the tree however. Inspection of the wood of the tree showed soft rot affecting much of the structure of the canopy. The removal of areas affected by soft rot however will not save this tree. The wounds to remove these areas were so large that the tree would not be able to properly heal.

At Makray Memorial Golf Club, we strongly believe that trees serve a significant purpose in the environment of the club grounds. Many of these trees have been alive long before the golf course ever existed. However we can not save all the trees from disease, failure or decay. We diagnose all trees with defects to determine if saving them is within the realm of possibility. Any tree that poses immediate risk to any employee or patron is immediately removed. If you have any questions in regard to tree safety and failure, you can contact me at

Thanks, and hopefully we will be out on the course soon

Timothy Christians
Head Golf Course Superintendent



November 27, 2012

Here is a post from Derek Settle of the Chicago District Golf Association.  It is about Pink Snow Mold caused by (Michrodochium nivale).  This is the earliest report of this disease that I am aware of in the region.  I normally see it in late winter.

It has been a strange year and there are many things showing up at strange times.  I find that what Derek sees in Chicago, we generally see here in Iowa.

The first three pictures are from North Shore Country Club in Glenview,  Ill.  They were taken by Derek on November 16.  They are on a Poa/bent 50/50 mix.

Derek is at 

Derek Settle, PhD
Director of Turfgrass Program
Chicago District Golf Association
11855 Archer Ave
Lemont, IL 60439
P 630.685.2307
C 785.341.9419


This is a slide from my teaching set showing the canoe shaped spores of Microdochium.  This is what you would look for under the microscope to determine if the symptoms are caused by Microdochium.

Slide of Microdochium



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.



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.