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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

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DROUGHT DAMAGE SHOWING UP THIS SPRING

April 10, 2013

Here are some interesting pictures from Rob Elder of Omaha Organics showing the impact of the drought this spring on Omaha lawns.  Damage this bad is a problem for the lawn care people.  You will have to spring seed, but that means that you cannot put down a standard preemergence herbicide.  These spring seedings generally turn to crabgrass and other annual weeds by midsummer. You can use siduron, which will allow bluegrass and ryegrass to emerge and give you some relief from the annual weeds.  If you are planting straight Kentucky bluegrass, Tenacity (mesotrione) can help with the annual weed problem.  However, both methods are expensive and difficult to do in a commercial operation.

I suspect that these area were primarily perennial ryegrass before the drought.  This is what we are seeing in our area.  The bluegrass lawns came back pretty well after the drought because of their rhizome system underground.  Whereas perennial rye thinned out and stayed that way.

Hopefully we will get more moisture this year and return to more normal conditions for the Midwest.
 

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QUACKGRASS WAS THE BIG WINNER IN DROUGHT

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.

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GOOD YEAR FOR WINDMILL GRASS

July 3, 2012

Windmill grass (Choris verticillata)   has been moving into Iowa in the last few years.  This summer I am seeing more of it than ever.  This is a spreading, warm-season weed with a light green color.  It gets its name from its distinctive seedhead that looks like a windmill.  The seedhead will detach from the plant when the seed is mature and it will roll like a tumbleweed and spread its seed to other turf areas.  It is also known as tumble windmill grass in some regions.

Roundup will kill it non-selectively, but it is a great seed producer and it will come back.  The new herbicide Tenacity (mesotrione) is labeled for it.  I have not tried this yet myself, but I hear that it works well if you are persistent.  If anyone has experience with this, let me know.

I took the pictures below this morning near Nevada, Iowa.  This is typical of where it occurs.  I generally see it along curb sides and in compacted area, although it can show up in more open turf areas.

 

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CRABGRASS APRIL 2

April 2, 2012

I did another check for germinated crabgrass today, April 2. I'm starting to see more of it peaking through in protected areas on campus. This is weeks earlier than normal.

I am not seeing it in rural areas or more exposed areas on campus yet.

Nick Dunlap got the first applications of our preemergence timing trial out this morning. It includes Baracade and Dimension at label rates. We will apply again on previously untreated plots on April 16 and May 1. I'll let you know what we see. We are not seeing any germinated crabgrass at the research station yet.

I previously recommended that you consider going two weeks early this year, which would be about April 15 in central Iowa. If your areas are protected sites in an urban environment, I would recommend applying as soon as you can. We will do Reiman Gardens this Wednesday, which is earlier than we have ever made applications to that site.

Remember that crabgrass is very susceptible to frost. If we get a late freeze, which I still think is likely, the problem will take care of itself. In the absence of a freeze, however, we could see a lot of crabgrass this summer.

Germinating crabgrass, courtesy of Andrew Hoiberg.

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CRABGRASS MARCH 23

March 24, 2012

I received these pictures from Grad Student Andrew Hoiberg on March 23. They were taken in a very protected area by animal science on ISU campus. I did another check of the areas on campus where I see crabgrass first each year on the morning of March 24 and still see no crabgrass germinating in these areas. I'll keep you posted on other developments.

These are the real thing. It is large hairy crabgrass. Notice the pointed leaf tip and the fine hairs on the leaf margin.

I would like more pictures from around the state as you see crabgrass emerge. I will get them up on the blog. This does appear to be one of the earliest springs in my 33 years here in central Iowa.

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KNOTWEED OR CRABGRASS?

March 23, 2012

The warm weather and the unusually large number of growing degree days (GDD) for late March have led to a lot of concern about early crabgrass germination.

First of all, let me tell you about my experience with this over the past 33 springs in central Iowa. I watch crabgrass germination dates very closely because of my research with preemergence herbicides. I have often been worried about early germination because of warm conditions in March and early April, only to find that cragbrass germinates at about the normal time, around May 1 in the Ames/Des Moines area. This is also true in cooler years when I anticipate late germination may occur later than usual. The germination is still around the normal time.

This year is one of the warmest in my experience and I’ll be watching the situation closely. At the research station we plan to apply applications of Dimension (dithiopyr) and Baracade (prodiamine) separately in test plots on April 1, April 15 and May 1 to determine what kind of crabgrass control we can expect in a warm year like this. I’ll keep you informed of the results as things develop. We will also discuss this work at field day on July 19.

We have had several calls and e-mails in the last few days about emerging crabgrass. I spent March 21 looking for any emerged crabgrass around town and around Veenker golf course. I did not find any. What I am seeing is a common problem at this time of year. Prostrate knotweed (Polygonum aviculare), which is a broadleaf species common in compacted areas around sidewalks and on in the center of sports fields, looks a lot like crabgrass as it emerges. This is one of the earliest germinating weeds in the landscape and is often observed in March and even in late February. While it is a broadleaf, it can look a lot like a grass when it first emerges. It is often mistaken for crabgrass by lawn care customers early in the season. It is a problem for lawn care specialists because the customers will often tell them that they have applied their preemergence herbicide too late. It is not until the leaves begin to mature that it becomes clear that this is a broadleaf and not a grass.

While I found knotweed everywhere I looked on the 21st, I did not see any crabgrass, even on bare soil on southern exposers where the crabgrass usually emerges first.

I did notice some interesting things about the knotweed. While this species is considered to be an annual in this location, it does appear that some of the runners may not have died during the unusually warm conditions this winter and that leaves were emerging from the runners. That is very unusual. I'm not quit sure of this yet and I will continue to watch this development over the next couple of weeks.

 

The picture below is of knowtweeed germinating from seed in March.

A close up of the plants shows that it is clearly not crabgrass, but it
does look like crabgrass from a distance.

 

I also saw quite a bit of annual bluegrass (Poa annua) which usually germinates in fall, but which can germinate in spring. This species can also be mistaken for emerging crabgrass.

 

 

The last picture is of an annual broadleaf that looks so much like crabgrass that it fooled me when I first saw it. Its texture and color and size exactly matched germinating crabgrass. The main difference is that the leaves are rounded on the end, whereas crabgrass will have more of a pointed leaf tip. I can see how people are easily fooled by these seedlings at this stage, however. I think that these emerging plants are knowtweed, but they are a little different and I'm going to continue to watch them over the next few weeks. If it turns out to be another species, I will let you know in a future blog.

So, what am I recommending as far as the best time to apply preemergence herbicides this spring?

I am currently telling people to go about two weeks earlier than they normally would. If you are used to getting them down by May 1, try to get them down by April 15. The timing will be later in Northern Iowa and earlier in Southern Iowa.

Dithiopyr (Dimension) has some post activity on newly germinated crabgrass and if you have to go later, that may be your best product.

If people call me on May 1 and ask if they should still treat, I'm going to tell them yes. I'm still betting that crabgrass germination will occur close to its normal time.

 

 

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CREEPING BELLFLOWER IN AMES LAWN

September 22, 2010

Here is the unusual weed of the week. It came from an Ames lawn. It looks like Ground Ivy (creeping charlie) except it does not have a square stem and does not have the mint odor. Also, it is spreading by underground rootstalks and not above ground runners.

It is Creeping Bellflower (Campanula rapunculoides). It is an escaped ornamental that has become an invasive weed. It has a blue, bell-shaped flower at some times of year, but in mowed conditions may go most of the season without a flower.

It is hard to kill. It is resistant to 2,4-D and many of the other common lawn herbicides. You will need something with Dicamba in it and it will still likely take several applications. Luckily, it is rare in Iowa.

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