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Summer Turf Diseases on Home Lawns

September 11, 2016

This past summer has been an exceptional year for diseases on turfgrass, and home lawns weren’t immune to these diseases either. Dr. Christian’s has mentioned several times this summer that this summer was the worst Brown Patch in Iowa he has seen in 30+ years. Summer temperatures often in the 80’s and lows in the upper 60’s with high humidity and rainfall made the conditions perfect for these summer diseases. The good news is that the temperatures seem to have cooled and repairs can be made to yards.

With the warm temperatures, ample rainfall, and high humidity this past summer, Iowa lawn’s endured prolonged periods of perfect weather conditions for brown patch (Rhizoctonia solani). This disease was noticed in Iowa from June on into September. It is often noticed as circular patches from a few inches to several feet.

Brown patch at the ISU Horticulture Research Station
Brown patch on creeping bentgrass putting greens at the Iowa State Horticulture Research Station.

The area in the patch can become killed and create a sunken patch, often though this disease will not completely kill the turf, but rather just thin those spots, which can recover with proper care after the weather conditions change. Brown patch lesions on leaves are easy to identify and are irregular tan or light brown in color with the edges of the lesions being a dark brown in color.

Brown patch lesions on turfgrass leaves
A close picture of brown patch lesions on turfgrass leaves.

Another problematic disease this summer was summer patch (Magnaporthe poae) which happens predominantly on Kentucky bluegrass and commonly occurs when temperatures are above 82. It is caused by a fungus that colonizes the roots. These patches often appear suddenly as small yellow patches, since the roots are affected, adding water will not help the declining turf health. As the grass dies it will turn a straw color. These patches often have areas inside of the patch that are not affected and seem healthy. Symptoms of summer patch will not be noticeable when the weather cools. Promoting healthy roots will help to minimize the impact of summer patch by regular aeration in the fall, mowing at proper mowing heights, and improving drainage in the yard.   

Disease on turfgrass lawn

If these diseases injured your turfgrass the fall is a great time to recover from them, as healthy turfgrass is the best way to combat weeds and disease next year. Make sure your yard is fertilized this fall, aeration each fall to improve gas exchanges to the roots and improve drainage making them healthier can help, follow proper mowing heights for the turfgrass species that are present in the yard, and overseed with more grass seed if large areas of dead turf exist.
Aerators can help improve drainage and promote healthy turf.
Aerators can help improve drainage and promote healthy turf.

One final note, several calls and emails this week have been related to people mistaking disease damage for chemical damage. Remember that typically disease damage will be patchy, while chemical damage would be a complete grass kill or in straight lines.  

Below are a couple pictures of disease damage on lawns from the Ames area:

Summer disease damage to a lawn in Ames


Turfgrass diseases can become a large problem is conditions exist for a long time.


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Summer Patch Showing Up On Kentucky Bluegrass Turf At Research Station

July 6, 2015

Summer patch, caused by the fungi (Magnaporthe poae), is showing up on Kentucky bluegrass turf at the research station in central Iowa in early July.  I am also getting some calls and pictures from people in the state asking about this problem.

This disease forms an interesting pattern in the turf.  The patches are 8 to 15 inches in diameter.  In early stages, they will have a brown ring around the outside and a green center.  In more advanced outbreaks, the entire area may become blighted.  The symptoms are often referred to as "frog-eyes".  There are other diseases that form frog-eyes, but these generally show up at other times of year.  Summer patch generally begins in early July in central Iowa.  I normally associate it with years that begin wet and then turn hot and dry.  In this case, the area is irrigated.  We have also had a wet spring and this area was not under moisture stress.

The development of the frog-eye is generally attributed to the fact that this organism is generally a saprophyte, an organism that feeds on dead organic material.  The infestation begins in the center of the spots and begins to move out as it consumes dead organic material.  Under the right conditions, the organism will begin to attack living tissue and forms the dead ring.  

Systemic fungicides that are taken up by the plant are the only materials that will control this disease.  It does little good to treat once the symptoms are present. The condition will go away by fall.  The area should be treated with systemic fungicides labeled for Summer Patch the next year before the symptoms develop.  This is of course hard to do and good record keeping is a must for this disease.

Core aeration in the fall can also improve growing conditions for the grass and may reduce the severity of the symptoms.  The pictures above are taken from an area where the disease appear nearly every year.  We leave the area untreated so that we can show the condition at the annual field day.  This years field day is on July 23, 2015.




August 29, 2014

Her is an interesting situation that I have not seen before.  The pictures come from Mike Vander Pol, superintendent at Emerald Hills golf course in Northwest Iowa.  This is on a Kentucky bluegrass fairway with a history of Summer Patch caused by the fungi  Magnaporthe poae.  The symptoms clearly look like Summer Patch, however, I would not expect the hyphae forming a myclial mass around the outside of the ring.  It was Pythium weather at the time that the pictures were taken, but Pythium is rare on Kentucky bluegrass and the mycelia mass is clearly around the circumference of the patches. 

I had Mike treat a test area with Teramec SP (chloroneb), a pythium control and send a grass sample to the Iowa State Plant Disease and Insect clinic for identification.  Mike reported to me that the Teremec did stop the hypha.  The laboratory was able to find oospores of pythium on the sample and runner hypae in the roots.  They were not able to clearly identify the species of the runner hyphae.

Evidently, the summer patch developed as is common on Kentucky bluegrass at this time of year.  This weakens the grass in the infected area.  That must have coincided with just the right conditions for Pythium development and the two diseases happened simultaneously.  Like I said earlier, I have not seen that before.


Dandelions in summer patch areas from last year

May 24, 2016

On July 6, 2015, I posted a blog about summer patch, caused by (Magnaporthe poae), on the turfgrass research area.  It was a major outbreak of this disease.  In late May, a few days ago, I was looking at the area.  The disease is not active now, but the interesting thing about the area is how dandelion seed landed in the dead part of the rings and germinated in the fall and spring. 


The first two pictures are from the post on July 6 of last year when the summer patch was active.  The last 4 are from May 20, 2016 showing the dandelions.  The dandelions had been treated with a broadleaf herbicide a week earlier.




From May 2016









It Is Summer Patch Time In Iowa

June 16, 2016

Here are a couple of great pictures from Nicholas May of True Green lawn care in Des Moines.  These pictures were taken south of Des Moines this week.  The disease is summer patch, caused by (Magnaporthe poae). 

For more information on this disease, search "summer patch" in older editions of this blog.

Summer patch requires systemic fungicides applied before symptoms develop.  If you have a condition like this that has already developed, you will need to core aerify in late summer and let it recover.  Watering the area next year will help and systemic fungicides applied before symptoms develop next May will help.  There is no reason to treat it with fungicides at this time.