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Name That Patch – Early Spring Brown Spots

March 28, 2011

Parts of the Midwest are getting hit with another round of snow but there is no denying that spring continues to inch closer by the day. In fact, before this last blast of winter weather, spring activities were slowly getting underway. Trees were beginning to break dormancy, bulbs were peaking through the soil, and lawns were starting to green up.

This process has already started across parts of the Midwest and some of you may have noticed patches, or areas of brown in your lawn. It’s typical to receive a number of questions from your clients about the cause of these brown spots during spring green-up. There are a number of reasons why these patches can appear and this article will address some of the most common reasons and discuss what action, if any, is needed to remedy the situation.

Dormant warm-season grasses
Most lawns in the upper Midwest contain cool-season grasses like Kentucky bluegrass, perennial ryegrass, and tall and fine fescues. Occasionally lawns, or parts of the lawn, will contain warm-season grass species. Examples of these could include zoysiagrass, buffalograss, or nimblewill. Whereas cool-season grasses grow best in the spring and fall, warm-season grasses prefer the mid-summer months and will remain dormant (brown) longer into the spring until warmer temperatures arrive.

If zoysiagrass or buffalograss are the cause of your brown spot there isn’t much you can do other than exercise patience until warmer weather arrives. Nimblewill can be selectively controlled with Tenacity herbicide. Tenacity herbicide will be made available to homeowners later this spring. Consult a lawn care professional for more information about Tenacity herbicide.

Dormant patches of nimblewill are very noticeable early in the spring.  Nimblewill can be selectively controlled with Tenacity herbicide.  Consult with a lawn care professional about the availability and use of Tenacity herbicide.


Warm-season grasses such as buffalograss are still brown while cool-season grasses such a fine fescues begin to green-up.

Leftover annual grassy weeds
Annual weeds such as crabgrass are always a concern and last year they seemed to be particularly troublesome. In lawns that had severe outbreaks, some of these annual grassy weeds may still be present. The good news is that you don’t have to worry about controlling leftover annual weeds. They have completed their lifecycle and are no longer alive. They did however drop seed and you may consider using a pre-emergence herbicide for the upcoming season.


Goosegrass, an annual grassy weed, is still present from the previous growing season. 

Snow molds
Damage from pink and gray snow mold is most evident shortly after the snow melts. The grass will usually appear off-color and be matted down. Chemical applications to control snow molds in the spring are seldom recommended as most of the damage has already taken place. You can help your lawn by raking up the matted areas of grass with a leaf rake. Chances are there is some live turf hiding underneath. The picture below shows an area of gray snow mold on the Iowa State University central campus.


Gray snow mold on the Iowa State University campus. 

Dog spots
Damage from animal urine will definitely create brown spots in the lawn. Where you can usually count on some recovery from snow mold damage, dog spots are very effective at killing grass. The best course of action is to remove the dead grass, break up the soil with a hand trowel or rake and re-seed the area. Note: Seed will not germinate and grow if a pre-emergence herbicide is to be used. The exception to this rule is when Tenacity or Siduron herbicides are used. Consult with a lawn care professional for more information about these products.


Man's best friend.  Undoubtedly charming, but damaging to grasses.

Salt damage
De-icing materials that contain sodium can be quite harmful to turf. Brown patches or areas of turf along driveways, sidewalks, or streets could be caused from salt damage. Depending on the severity of damage, reseeding may be necessary. Aerification and watering (or rainfall) can help flush salts through the soil profile and improve the conditions of the site.

Marcus Jones
Graduate Research Assistant

Nick Dunlap
Undergraduate Research Assistant



June 24, 2013

Here is some information from former graduate student, Nick Dunlap, on some work he is doing with bermudagrass control in ryegrass in Virginia. 

From Nick Dunlap:
The images show the effect of topramezone on bermudagrass in bentgrass and ryegrass 4 days after treatment.  Bleaching typical of HPPD inhibitors is easily seen on the bermudagrass.  Topramezone was applied at 0.25 oz/acre and 0.75 oz/acre on bentgrass fairways and ryegrass shortcut, respectively.  Both applications were applied through a carrier volume of 2 gal/acre.

Nick has been having pretty good luck turning the bermudagrass white, he will keep us posted about control. 

I did some checking on this new product labeled as Pylex from BASF.  Here is what I found at
Pylex™ herbicide is the standard for the control of Bermudagrass and goosegrass in cool-season turf, providing unmatched performance on these difficult-to-eliminate weeds. It has also shown excellent control of nimblewill, crabgrass, clover, speedwell, and others. Pylex™ herbicide should always be used with a crop oil concentrate (COC) to improve herbicide coverage, resulting in improved weed control.

Pylex™ herbicide has shown it is safe to most cool-season grasses such as Kentucky bluegrass, tall fescue, fine fescue, and perennial ryegrass.  It has shown varied tolerance on bentgrass (moderate to severe injury) and annual bluegrass (minimal to moderate injury) at labeled use rates. Warm-season turfgrass is sensitive to Pylex herbicide, with the exception of centipedegrass, which is tolerant.

The web indicates that it should be available by mid-June.





November 13, 2012

Quackgrass (Elymus repens) is known for its long clasping auricles and its extensive rhizome system.  It is one of the most persistent and difficult to control weeds in cool-season lawns.  Rhizomes give this species an ecological advantage over other grasses during extended dry periods.  While Kentucky bluegrass also has a rhizome system, quackgrass has a more extensive system and will out compete Kentucky bluegrass in dry years.

This was the case in this year's drought in the Midwest.  Lawns went through an extended period of dormancy that in many areas lasted for months.  This fall, we are seeing Kentucky bluegrass lawns recover. But wherever there was quackgrass in the lawn, it has gained an even bigger foothold.

Last week, I was asked to look at a lawn that one of my students cares for through his lawn care service.  It had been a mostly Kentucky bluegrass lawn up to this year, but following the drought, nearly everything that is recovering is quackgrass from the rhizome system.

Roundup will kill it, but the problem is that Roundup generally does not translocate through the entire rhizome system.  When you reseed, there is always some living rhizome tissue and quackgrass returns.  I generally recommend repeated applications of Roundup, followed by sodding.  Even that extreme treatment generally fails, however, and the quackgrass returns.

Figure 1.  Long clasping auricles of quackgrass.

 Figure 2.   Quackgrass rhizomes.

Figure 3.  Lawn in central Iowa that is nearly all quackgrass following the drought of 2012.



September 18, 2012

Since I put up the post on August 2 about bermudagrass in Iowa, I have had several other calls about bermudagrass invading lawns and sports fields.  These calls have come from Burlington, Council Bluffs, Des Moines, Keokuk, Davenport, and Red Oak.  I have also been getting samples to identify.  I have had more contacts on bermudagrass in the last 8 weeks than in the previous 33 years combined.  The mild winters and hot summers are resulting in this species becoming a significant problem in some regions.

The usual questions is, “How can I kill it?”.  There is no selective control in cool-season turf.  You have to kill it with Roundup.  It is very hard to kill.  It will likely take several repeat applications of Roundup, and even then, its extensive rhizome system results in regrowth.  Complete soil sterilization with methyl bromide may be the only sure way to remove it from critical areas like sports fields and sod fields.  Of course a couple of cold winters would also take it out.  That is the reason it was not here before.

Here are some pictures that I received from Eric Van Ginkel of the Iowa Cubs concerning the Dowling High School softball field.  The sodded this field just 5 years ago with Kentucky bluegrass and bermudagrass has spread extensively in the last couple of years.

If anyone else has a major infestation, send me some pictures and I'll get them up on the blog.


Figure 1.  The Dowling softball field.  This are the biggest patches of bermudagrass that I am aware of in Iowa.

Figures 2 and 3.  Eric wrote that these patches were discolored by an herbicide.  He did not say which herbicide, but it looks like tenacity.

Figure 4.  The extensive stolons of bermudagrass.  This is what makes it spread so fast.



April 10, 2012

With the warm weather that we have had, people have been asking about whether they should seed now or wait a few weeks.

Spring seeding is hard, no matter when you do it. Spring seedings often turn to crabgrass and other annuals and may take a year to mature into a real lawn. You can use a selective preemergence herbicide called Siduron which will selectively kill the annuals and let the perennials like Kentucky bluegrass and perennial ryegrass emerge, but that is expensive and difficult.

The best time to seed remains late summer to early fall. I would set August 15 as the best time to plan your seeding in central Iowa.

If you must spring seed, give it a little time yet. I am currently telling those who contact me to wait until after May 1. As we saw this morning, we are not past the frost-free days yet. Seedlings, particularly perennial ryegrass, can be susceptible to cold temperatures in the spring.

If you have to spring seed, I would recommend the application of Siduron with the starter fertilizer to control the annuals. If you end up with a lawn of crabgrass, don't give up. The perennial grasses will be in there. The annual will die in the fall and next spring you can put on a standard preemergence herbicide to control them.

Other standard preemergence herbicides will not work at the time of seeding. They will kill the crabgrass, but they will also kill the grasses that you are trying to seed.

The new herbicide Tenacity (mesotrione) can be used for spring seeding of Kentucky bluegrass, but leave that to the experts. Your local lawn care professional can tell you more about the product.



July 7, 2011

Nimblewill (Muhlenbergia schreberi ) is a warm-season perennial grass with a fine texture and a gray-green color. It spreads by stolons and forms a dense matt in cool-season lawns. It has a rolled vernation and a membranous ligule with jagged edges. It looks a little like creepting bentgrass, but it does not have a long membranous ligule that typifies bentgrass and has fine hairs around the collar. It forms a narrow spike-like panicle of seeds, with each seed having a fine awn (hair) at its tip (Figure 1).

It has been nearly impossible to control once it has become established in the lawn. It can be killed by nonselective herbicides, but it is also a good seed producer and it often returns from seed. It is a warm-season species and it looses its chlorophyll in the fall and takes on a bleached, straw-like appearance that makes it stand out in cool-season lawns. It is sometimes referred to as ‘wire grass’ in parts of the Midwest.

Tenacity (mesotrione), was released into the lawn care market in the spring of 2011. It had been available for a few years in the sports turf and golf markets. This material can selectively control nimblewill in Kentucky bluegrass turf. It is also labeled for the control of creeping bentgrass in Kentucky bluegrass and for the pre and postemergence control of crabgrass.

The pictures below are from the lawn of our "answer-line" person in the department, Richard Jauron. Richard gets a number of questions on nimblewill control and decided to do a test in his own lawn. These pictures are from the 5th of July, 2011. Richard will continue to update us on his experience with the material throughout the season. The material will turn susceptible weeds snow-white when it is first applied. It does take at least two applications for complete control of nimblewill, and may take more treatments. Remember too that nimblewill is a good seed producer. We will follow this through next season as well and not stop until control is complete.


Figure 1. Seed head of nimblewill with "awns".

Initial effect of tenacity on nimblewill in Richard's lawn. The white color is a typical response to this herbicide. Richard will repeat apply two weeks after the first application.