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Methods of Predicting Crabgrass Emergence

(By Jared Hoyle, KSU Turfgrass Research and Extension)

This morning when I cranked my truck up and headed to the office it was 25 deg F.  Just a couple days ago it snowed.  Just before that it was 80 deg F.  What is going on with the weather? (Every time I make that statement, someone says “Welcome to Kansas!”) With the fluctuating weather and temperatures I get the question “What date do I need to put my preemerge herbicide out on?”

Well this is a trick question because there is no correct answer for it.  Here are some of my thoughts on preemerge timing.

As soon as that first warm front comes through everyone gets excited and ready to work in their lawn.  I have even heard the comment that spring and summer are going to come early this year.  Are they right?  I don’t know but it is something to think about.

But as soon as we get excited about the warm weather we have another cold snap.  So we got all excited and talked about weeds germinating early and needing to get out our preemergence herbicides because the forsythias are blooming. But what happens when it gets cold?  Any crabgrass that “might” have germinated is now dead because of the cold temperatures. So this brings up a lot of discussion between myself and some colleges. Here are just some of the questions we are asked and a couple of comments.

Why do we recommend around April 15th for most of Kansas to put out a preemerge in our lawns?

– April 15th is about the time that we have our “last” frost/freeze. (This also shifts to April 30th in Western/North Western KS and to April 1 in Eastern/South Eastern KS.) This goes along with our concept that I was talking about before.  Even though it may be getting warm we are still might have a cold snap that would end up killing the crabgrass if it emerged. This is the same concept of why we don’t plant crops until after this date as well.  (Something I don’t know anything about but that is what I figure…..)

Should we use soil temperature at 1″ to predict when to put out preemergent herbicide applications?

-Soil temperatures are a great way of determining when to apply your preemerge herbicide.  Scientists say when soils reach a daily average of 55 deg F for about 5 days at a 1″ soil depth then it is time to put out your preemerge.  Well say you go out and measure your soil temperature at 1″  you are not going to get a daily average, you are getting a single point in time.  Does that really represent what is going on?  What if you are maintaining many different properties.  It is not practical to obtain that information.  Good news is that KSU has a website (http://mesonet.k-state.edu) that you can click your closest weather station and get daily maximum and minimum soil temperatures where you can then calculate a daily average.  Bad news it only give you a 2″ or a 4″ soil temperature.  But using the 2″ soil temperatures are going to give you a better idea of the daily averages then going and taking one measurement.

The forsythias are blooming but my redbuds aren’t. Do I still put my preemergent herbicide out?

– This is called phenology – the study of cyclic and seasonal natural phenomena, especially in relationship to climate, plant and animal life.  Many people believe that when the forsythias are blooming then crabgrass is germinating.  That is not 100% true.  When forsythias are in full bloom then we need to be getting “ready” to get our preemerge applied.  Even though we see that this is a good indicator, Dr. Fry and others reported in a study that ornamental plant flowering is not always a good way to predict crabgrass germination and emergence. (Fry, J., S. Rodie, R. Gaussoin, S. Wiest, W. Upham, and A.Zuk. 2001. Using flowering ornamentals to guide application of preemergence herbicides in the Midwestern U.S. International Turfgrass Soc. Res. J. 9:1009-1012.) There are some things to consider when utilizing phenology for crabgrass germination and emergence.  Not all forsythias will bloom at the same time.  It determines where that plant is located in the landscape.  There are micro climates in the landscape.  Think about plants located in roadway medians.  They are typically warmer due to cars and the concrete and asphalt in close proximity.  The same thing goes with crabgrass germination.  Crabgrass will germinated sooner in areas that are warmer, for example (next to sidewalks, bare ground, etc.).

Crabgrass emerging in bare ground earlier than turf

I have heard about growing degree days to predict crabgrass germination. What is that?

– Growing degree days (GDD) use air temperatures instead of soil temperatures within a formula to get a cumulative number of growing degree days.  Using base 50 deg F, once you get to about 200 GDD then crabgrass will start to germinate.  Don’t want to calculate GDDs, don’t worry there is a website that will do it for you. http://www.gddtracker.net  Just enter your area code and click on crabgrass germination on the right side and it will give you the total GDD. It will also show you a prediction for the next couple of days too. GDD do not go backwards, they only accumulate.

So to put this all in perspective using the prediction methods mentioned above this is what we got;

Today is March 14th so using the calendar model for Manhattan we would not put our preemerge out until closer to April 15th for Manhattan.

Using the 2″ soil temperature method because that is what is available to us our daily average soil temperatures (Deg F) have been;

9-Mar 47.6
10-Mar 45.4
11-Mar 43.65
12-Mar 41.15
13-Mar 39.65

With this method we would assume the 1″ soil temperature is higher but we are not to the 55 deg F mark yet. So we are getting close to putting out our preemerge herbicide.

In my back yard my forsythias are blooming.  So that means if I am using the phenology method I need to be getting ready to apply my preemergence.

Lastly, using the GDD model we are at 85 GDD. So I still have some time but getting close.  Remember though that you can get more than one GGD in one calendar day and if I look at the future (prediction on the GDD Tracker website) on March 20th Manhattan will be at 111 GDD. So just in 6 days we would have gained 26 GDD.

Now these rules, concepts, ideas are not bullet proof but it is something to think about when planning your lawn care program.  There is not magic date for anything that you do to you lawn.  You need to make sure you keep up with the temperatures, soil temperatures, precipitation, etc.  The more you know what is going on with your turfgrass the better you will be able to predict crabgrass preemergent applications.  Use more than one method.  This is going to give you the best idea of what to do!

Now by this weekend we are going to get a little warmer but again looking at the 10 day forecast it might get cold again…. Just something to think about.  I hope this got you thinking as a turfgrass manager and how this is going to help you choose products if you are going to have to get applications out earlier or even later after crabgrass has emerged.

Always remember to READ THE LABEL for the correct rate, turfgrass tolerance, and specific instructions before application!!!

***Mention of trade names or commercial products in this article is solely for identification purposes and does not imply recommendation or endorsement, nor is criticism implied of similar products not mentioned by Kansas State University.***

Don’t forget to follow me on twitter @KSUTurf.

Also, visit our facebook page www.facebook.com/KSUTurf

 

New Turfgrass Selfie Series on YouTube – Knotweed Control

(By Jared Hoyle; KSU Turfgrass Research and Extension)

selfieWe have just started something new on Youtube and it is call the Turfgrass Selfie Series.  We will be uploading short informational and educational videos about turfgrass management to our new Youtube page.  These videos are not professional done as we are turfgrass researchers and not very good videographers. (I fell like I did pretty good making this video with my iPhone. Hopefully we will get better at making videos in the future!)

The first video in the series is on Knotweed control. Check it out!

POST Control Options for Goosegrass

(By Jared Hoyle; KSU Turfgrass Research and Extension)

goosegrassGoosegrass (Eleusine indica) is a summer annual weed that typically germinates after crabgrass in the spring.  That is about when the soil temperatures consistently reach approximately 60° F.  Like crabgrass, goosegrass is best controlled with a preemergence herbicide.   Herbicides that contain the active ingredient oxadiazon work very well.  Other preemergence herbicide efficacy can vary.

But as it seems like everyone has already put down preemergence herbicide so, you have nothing to worry about.  Well what if you didn’t?  There are some post application control options.

To determine what herbicide you want to use this summer to control goosegrass, that might have escaped your PRE treatment or maybe you have the ‘itch’ to go kill some goosegrass, it all depends on the turfgrass you have.  If you have cool-season turfgrass then you can use fenoxaprop (Acclaim Extra), fluazifop (Fusilade II), tropramizone (Pylex), or MSMA (golf courses and sod farms only!).  You will probably have to do more than one application if the goosegrass is tillered out.  Sulfentrazone (Dismiss) is also effective on goosegrass if it has not tillered out yet.

Bleaching of goosegrass from topramazone application
Bleaching of goosegrass from topramazone application

Now if you have bermudagrass or zoysiagrass then you can use Tribute TOTAL (thiencarbazone + foramsulfuron + halosulfuron).  Fusilade II and Acclaim Extra that works in cool-season grass can also be used on zoysiagrass.  If you mix these products with triclopyr (Turflon Ester Ultra or Triclopyr 4) then you will get better results.

Always remember to READ THE LABEL for the correct rate, turfgrass tolerance, and specific instructions before application!!!

I hope the poem wasn’t boring but added a little fun to this turfgrass weed science blog post.

Hope everyone has a great rest of the week and weekend!

***Mention of trade names or commercial products in this article is solely for identification purposes and does not imply recommendation or endorsement, nor is criticism implied of similar products not mentioned by Kansas State University.***

Don’t forget to follow me on twitter @KSUTurf.

Also, visit our facebook page www.facebook.com/KSUTurf

A Cautionary Tale of Herbicide Application…

(By Jake Reeves; KSU Turfgrass Research and Extension)

This spring, when the rains began to come, I started to notice a slight discoloration in my front yard next to my fence. The area was very shaded and has always struggled, so I thought nothing of it. However, as the weeks passed, the area became more defined with wilt and it was clearly showing itself as a “man-made” phenomenon.

Thinking back through my maintenance, there was only one thing that could have caused that shape and slow death: the herbicide I had sprayed uphill of the site to maintain bare ground weed control in my mulch.

herbicide movement 1

The history… I developed a bad habit of maintaining empty large bed areas with bare ground herbicides when I lived on an extremely flat property at my last house. I hate weeding and the fewer applications I have to go out and make each year, the better.

I had used bare ground herbicides frequently at my job to maintain fence lines and other areas to cut down on weed eating due to a limited labor force. Over those few years I had little to no herbicide movement from the sites that I sprayed. That created a false sense of invincibility in my herbicide applications, which is never a good thing.

herbicide movement 2

Fast forward to today… Unfortunately for my lawn, my property has a pretty hefty back to front slope and a lot of water moves over it when it rains. That means that my property is a prime area for herbicide movement and this spring has proved that.

So pay attention to your site and THE LABEL! Trying to cut corners will eventually come back to haunt you. Chemical companies put large amounts of money into researching for those labels to give you instructions so you don’t encounter these issues.

My lawn and my pride have paid the price for my undeserved hubris. Thankfully, given a little bit of time for the herbicide to break down in the soil and some grass seed later this fall, things should be repaired.

-Jake

Always remember to READ THE LABEL for the correct rate, turfgrass tolerance, and specific instructions before application!!!

***Mention of trade names or commercial products in this article is solely for identification purposes and does not imply recommendation or endorsement, nor is criticism implied of similar products not mentioned by Kansas State University.***

You still have time! Preemergent Herbicides

(By Jared Hoyle, KSU Turfgrass Extension Specialist)

Pre-emergent (PRE) herbicides prevent summer annual weed (For Example, crabgrass, goosegrass, annual sedges, and spurge) seeds from developing into mature plants.  The reason we use PRE herbicides for summer annual weed control is because these summer annuals come back every year from seeds.  So if we can stop the seed from growing then we don’t have to deal with the weeds later in the season.

For all that don’t know how a PRE herbicide works here is a very short explanation.  They do not keep the seed from germinating but kill the young germinating plant.  With few exceptions they have no effect on existing plants, so they must be applied before germination.

But like in everything in life there is an exception.  Dithiopyr can kill crabgrass as long as it is young (two- to three-leaf stage, see photo below of three leaf crabgrass) and still have some residual for continued PRE activity. It doesn’t last as long as some of the other PRE herbicides but there is flexibility if you miss your window of opportunity to apply.

Slide1

So when do I put out the PRE application for summer annual weed control? Well, it depends on many things.  What summer annuals you have? Where are you located in Kansas?  Many times turfgrass managers center their PRE applications around crabgrass germination.  Crabgrass typically begins to germinate around May 1 or a little later in KS. April 15 is a good target date for applying a PRE because it gives active ingredients time to evenly disperse in the soil before crabgrass germination starts. The April 15 target works well for most of the state, but for southeast Kansas April 1 is more appropriate, and for northwest Kansas May 1 is best.  Additionally, weather varies from one spring to the next, and with it the timing of crabgrass germination. Some turfgrass managers base their PRE application around the bloom of the Redbuds but other ways can be used as well.  Crabgrass germinates when the soil at approximately 1 cm deep reaches 55° F.  So watch your soil temperatures to see when the soil consistently reaches 55° F. Here is a great website that will give you soil temperatures for your area.

http://mesonet.k-state.edu/weather/historical/

PRE herbicides do not last forever once applied to the soil. Microorganisms and natural processes begin to gradually break them down soon after they are applied. If some products are applied too early, they may have lost much of their strength by the time they are needed.  Additionally, PRE herbicides have different half-life, Koc, water solubility, and vapor pressure. This can determine how fast microbial, chemical and physical decay occurs along with infiltration, volatilization, leaching, and run-off.

Slide6

Therefore, not all PRE herbicides are created equal.   Here is a list of PRE herbicides, the weeds they target and some concerns that you might want to know before applying.

Active Ingredient Weeds Controlled Concerns or Comments
benefin summer annual grasses, annual bluegrass, some-small seeded broadleaves Do not use on golf course greens.
prodiamine summer annual grasses, annual bluegrass, henbit, chickweed, spurge, some-small seeded broadleaves Only apply to well established turfgrass.
bensulide annual grasses, some broad-leaves Do not use on putting greens composed of  > 50% Poa annua.
florasulam broadleaves, dandelion, prickly lettuce, clover Packaged with Dimension 2EW, florasulam great cool temperature activity, Prevents flowering in some broadleaves (dandelions).
dithiopyr summer annual grasses, annual bluegrass, yellow-woodsorrel, some small-seeded broadleaves PRE and early post-emergence activity on crabgrass.
isoxaben broadleaves such as chickweed, henbit, spurge, plantain, others Tank-mix with a grass herbicide for broader spectrum.
pronamide annual bluegrass, perennial ryegrass, other grassy & broadleaf weeds. Do not use on cool-season turf. Restricted use pesticide.
pendimethalin summer annual grasses, annual bluegrass, yellow-woodsorrel, some small-seeded broadleaves Not recommended for turf severely thinned due to winter stress.  Split applications can be made for extended control.
metolachlor annual bluegrass, crabgrass, sedges Do not use on cool-season turf.
simazine summer annual grasses, annual bluegrass, henbit, chickweed, spurge, some-small seeded broadleaves Do not use on cool-season turf.
ethofumesate annual bluegrass, annual grasses, some annual broadleaves See label for reducing annual bluegrass in cool-season turf.
oxadiazon summer annual grasses includinggoosegrass, annual bluegrass, some-small seeded broadleaves Ronstar G and Oxadiazon 2G are only formulations labeled for use on cool-season turf.
indaziflam annual grassy and broadleaf weeds in turf Do not use on cool-season turf.
oryzalin summer annual grasses, annual bluegrass, some-small seeded broadleaves Do not use on cool-season turf except tall fescue. 
dimethenamid bittercress, crabgrass, goosegrass, purslane, sedges, spurge On golf courses: Can be used on cool- and warm-season.  Other turf areas: Warm-season only.
siduron crabgrass, bermudagrass (suppression) Does not control goosegrass or annual bluegrass.

Information in this table was acquired from “Turfgrass Weed Control for Professionals” by A. Patton and D. Weisenberger, Purdue University. For more information about purchasing this publication ($12.00) for complete information see;

https://mdc.itap.purdue.edu/item.asp?Item_Number=AY-336#.VTENo94aj8s

For a digital copy (only $10.00);

https://mdc.itap.purdue.edu/item.asp?Item_Number=AY-336-W#.VTENy94aj8s

***There are many combination PRE herbicides that combine these active ingredients with each other and with other POST-emergent herbicides***

Always remember to READ THE LABEL for the correct rate, turfgrass tolerance, and specific instructions before application!!!

***Mention of trade names or commercial products in this article is solely for identification purposes and does not imply recommendation or endorsement, nor is criticism implied of similar products not mentioned by Kansas State University.***

Don’t forget to follow me on twitter @KSUTurf.

Also, visit our facebook page www.facebook.com/KSUTurf

Non-Selective Bermudagrass Removal

(By Jared Hoyle, KSU Turfgrass Research and Extension)

For the short time I have been in the turfgrass business, I always get asked the question, “How do I kill bermudagrass?”  And before I can give the recommendation of multiple applications of glyphosate (≥ 3 lbs ae/gal) at 3 qts/A over the growing season (May, July, and September) and waiting three to four weeks for regrowth before making the follow up application, I get the response “That doesn’t work.”

To help out you can add 24 fl oz of fluazifop (Fusilade II) to the tank and it will help with bermudagrass control over the glyphosate application alone.  Remember that fluazifop has some soil residual so it can stay in the soil for some time.  So, wait 30 days before reseeding if you apply it to bare soil or 14 days if you apply it to turf. But I would still get  the response “That doesn’t work.”

Well, I got to talking with a couple of turfgrass managers about this application process and started to ask the question, “What if we are wanting to renovate during the Spring?”

Research in the past has resulted in better control with perennial broadleaf weeds, like dandelions, in the Fall compared to Spring applications. So after a little brainstorming we decided to apply this concept to controlling bermudagrass before dormancy.  This way the bermudagrass would have the dormant look throughout the winter but would be ready for renovation in the Spring.

Research Trial Location Stagg Hill (October 3, 2013)

Research was conducted at Rocky Ford Turfgrass Research Center and Stagg Hill Golf Course in Manhattan, KS to determine bermudagrass control with glyphosate, mesotrione, and fluazifop applications prior to dormancy.  Applications were made on October 3, 2013.  Treatments consisted of a non-treated control, glyphosate (6 pt/A), mesotrione (8 oz/A), fluazifop (24 fl oz/A), glyphosate (6 pt/A)+ mesotrione (8 oz/A), glyphosate (6 pt/A) + fluazifop (24 fl oz/A), mesotrione (8 oz/A)  + fluazifop (24 fl oz/A), and glyphosate (6 pt/A)+ mesotrione (8 oz/A) + fluazifop (24 fl oz/A).  All treatment included at 0.25% V/V non-ionic surfactant (NIS).  All treatments were 100% brown (dormant) bermudagrass by October 31, 2013.

Rocky Ford Trial Location (October 17, 2013)

What we found initially is that there were drastic differences between these two locations.  Bermduagrass control at the Stagg Hill location out performed the Rocky Ford location.  We believe this was due to the differences in bermudagrass cultivars.  The Rocky Ford Location was ‘Midlawn’ bermudagrass and the Stagg Hill location is a common bermudagrass.

Rocky Ford Trial Location (May 14, 2014)

At Rocky Ford the untreated control reached 100% bermudagrass cover on June 12, 2014.  At that time treatments that included glyphosate resulted in <18% bermudagrass green cover.  On June 13, 2014 the untreated control at Stagg Hill was 100% green bermudagrass cover.  All other treatments that included glyphosate resulted in <9% green bermudagrass cover.

What is really surprising is the rating that was conducted just a couple of days ago. At Rocky Ford all bermudagrass treatments recovered to at least 90% green bermudagrass cover by July 14, 2014.  But the Stagg Hill location is still showing significantly more control.  Glyphosate, glyphosate + fulazifop, glyphosate + mesotrione, and glyphosate + mesotrione + fluazifop resulted in only 27%, 26%, 17%, and 23% green bermudagrass cover, respectively.

Rocky Ford Location (June 3, 2014)

These results suggest that a single application of glyphosate in the Fall prior to bermudagrass dormancy can aid in non-selective bermuagrass removal.  We are going to repeat these trials again this year along with trying some Spring applications in combination to see if we can increase bermudagrass control.

Always remember to READ THE LABEL for the correct rate, turfgrass tolerance, and specific instructions before application!!!

***Mention of trade names or commercial products in this article is solely for identification purposes and does not imply recommendation or endorsement, nor is criticism implied of similar products not mentioned by Kansas State University.***

Don’t forget to follow me on twitter @KSUTurf.

Also, visit our facebook page http://www.facebook.com/KSUTurf