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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



July 16, 2014

On May 28, Dr. Zach Reicher of the University of Nebraska and John Newton, CGCS at the Iowa State University golf course (Veenker Memorial) began a test of buffalograss (Buchloe dactyloides) as a grass for roughs.  Buffalograss is a warm-season species and is generally not used in our region.  Our wet climate generally assures that competing weeds out-compete the buffalograss over time and it is more difficult to maintain than the standard Kentucky bluegrass.

The release of Tenacity (mesotrione) gives us a new tool to fight weeds in buffalograss and the test is designed to determine if buffalograss is a viable option in our climate, if we can keep competing weeds from becoming a problem.  Zach's recommendation on the rate of Teancity is as follows:


PRE on new seedbeds:  8 oz/A X 2, second app is about 4 weeks after germ maybe earlier if needed. Nonionic surfactant (NIS) in the last app.

POST on new seedlings: 5.3 oz/A X 3, two week intervals. NIS in the last two apps, but probably not the first app just to maximize safety.

POST on established buffalograss: 5.3 oz/A X 3, two week intervals. NIS in all  apps.

The buffalograss was a turf-type variety called "Bowie" (Gr-742).  An area a little larger than an acre between two fairways was killed with Roundup (glphosate) in mid-May.  Three methods of establishment was used.  One third of the area was tilled and seeded at 2 pounds of burs per 1000 sq.ft. The same rate of seed was slice-seeded into another one third and the final area was core aerfied and seeded.  The areas were irrigated until the seed germinated.  Tenacity was applied the week of June 9 and again on June 20.  We will continue to monitor the area for the next couple of years and keep you posted as to how it is working.

John and Zach on the day of seeding, May 28, 2014

Tilled area in the background and slice-seeding in the foreground. 

 Areified area was seeded with a drop seeder.

The area flooded in late June and was underwater for two days.

This is the site on July 16 (this morning).  The grass survived the flood well, except for one low area in the tilled area.  It is coming in well and the Tenacity has worked well on most weeds.  There is some prostrate spurge and yellow nutsedge, but most other weeds were controlled. 



November 22, 2010

This is a final summary on the recovery of the intramural field on campus that was damaged during the flood in August.

The first picture was taken a few days after the flood. The bluegrass/rye turf is dead. The grasses that survived are all warm-season grasses. Most of it is Bermudagrass, but there is also Zoysiagrass and Buffalograss on the site. This grass was established over the steam tunnel several years ago.

The second picture shows Kentucky bluegrass beginning to recover from rhizomes. It was taken a couple of weeks after the flood waters receded.

The third picture shows one of the turf lab groups on the site in September. They are standing on the warm-season grasses. The surrounding area was reseeded shortly after the flood and the blue/rye area has nearly recovered.

The final picture was taken in November of 2010. The blue/rye area has completely recovered and the warm-season grasses have gone dormant for the season. Little by little, the campus is returning to normal. The final bill for the flood damage was in the range of 50 million dollars.



August 24, 2010

These two pictures are both from the intramural field on ISU campus. The first one is from last November. It shows a strip of warm season grasses that have been planted on the steam tunnel that runs through the area. They include bermudagrass, zoysiagrass, and buffalograss. They are all dormant as would be expected in November. The Kentucky bluegrass/perennial ryegrass turf is green.

Now look at this picture taken yesterday, Aug. 23, 2010, approximately two weeks after the flood. This area was completely under water for at least 3 days. The bluegrass/rye is dead (although I think the rhizomes of the bluegrass are alive) and the warm-season grasses have recovered. This is a good demonstration of how well warm-season species can take flooding.