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Category: Weeds

Spring cool-season turfgrass seedings – Why they fail

(By Jared Hoyle and Ward Upham, KSU Research and Extension)

When we talk about cool-season turfgrass seeding timing I always think the fall.  Well all around town I keep seeing more and more people seeding their lawn this spring.  I don’t want to say you are wasting your time because there are a couple reasons that you might need or have to seed in the spring but most success is achieved if seeding cool-season turfgrass in the fall.

There are several reasons Kentucky bluegrass and tall fescue lawns are better seeded in the fall than in the spring.

These include:

  • Some of the most serious lawn weeds such as crabgrass and foxtail emerge in the spring. Since they are warm-season weeds, they will compete and often crowd out young, tender cool-season grasses during the heat of summer.
  • The most stressful time of year for cool-season grasses is summer, not winter. Poorly established lawns may die out during the summer due to heat and drought stress.
  • A lawn often gets more use during the summer, leading to increased compaction and traffic stress. Young plants have a hard time surviving the high traffic during the summer.
Weed competition when establishing cool-season from seed in the spring.

If an area needs to be established in the spring, sodding is much more likely to be successful than seeding. Sodding provides stronger, more mature plants that are better able to withstand stress and prevent weed invasion.

Every homeowner needs to know the difference between Roundup & Roundup for Lawns.

(By Jared Hoyle, KSU Turfgrass Research and Extension)

The other day after eating dinner I was watching TV trying to finally relax.  A commercial came on about Roundup for lawns….  I thought to myself “Oh man, This is going to cause a lot of confusion!”

There is a huge difference in the active ingredients in Roundup compared to Roundup for Lawns.  That is why it is so important to know what you are applying.

Dr. Kevin Frank at Michigan State University just posted a great article about the difference between Roundup and Roundup for Lawns.  Check it out here.

http://msue.anr.msu.edu/news/difference_between_roundup_and_roundup_for_lawns 

Every homeowner needs to know the difference!

I will make a prediction.  Due to the confusion with the names of these products.  I will get at least one phone call this year where someone has killed their entire lawn with glyphosate because they thought they could use Roundup on their lawn and they put out the wrong product.

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

Wild garlic control in turfgrass

(By Jared Hoyle, KSU Turfgrass Research and Extension)

Did you know there are benefits to eating garlic?  It is highly nutritious but has very few low calories, it can help combat sickness, it can reduce blood pressure, and more.

Around Manhattan I have been seeing a lot of wild garlic in lawns.  Now don’t go out and eat that wild garlic. We are now talking about the turfgrass weed wild garlic and not the garlic you consume.

Wild garlic is more obvious in the winter and early spring because this weed will grow above the turfgrass canopy and is easily noticed.  Wild garlic is a perennial bulb that has a grass like appliance.  It emerges in late winter and early spring.  The leaves are straight and smooth.  The way to tell the difference between wild garlic wild onion is by tearing the stem to see if it is hollow or solid.  It if is hollow then it is wild garlic.  If it is a solid stem then it could be wild onion.

This weed tolerate a wide range of soil conditions but I have noticed it more in low maintenance areas.

Photo credit – Auburn University Turfgrass – http://cses.auburn.edu/turfgrass-management/weed-identification/wild-garlic/

Control of wild garlic in cool-season turfgrass is more difficult then in warm-season turfgrasses.  For fair control use 2,4-D or one of the many combinations of 2,4-D, MCPP and dicamba.  This products have shown to have limited control.  The ester formulations of 2,4-D are more effective than amine formulations.  Applications in the late fall and early spring when there is adequate foliage is best.  To increase uptake, mowing before application may help.

In warm-season turfgrass metsulfuron or metsulfuron + sulfentrazone and sulfosulfuron provide very effective control.  Applying these products in late March (Right now!) on a warm day above 50 deg F (Right now!) when there is good soil moisture (Right now!) will increase efficacy.

If you got wild garlic, right now is the time to go out and get it.  Not to mention if you have any other broadleaf weeds you will get some control of those as well!

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

Keep it mowed and let mother nature take control

(By Jared Hoyle, KSU Turfgrass Research and Extension)

One of the most common weed control recommendations for winter annual weeds is “keep it mowed and let them die because of the warmer weather”.  Well right now it is March 30th and it is prime winter annual weed growing weather.  Yeah, it might warm up in the next week but what if this is what we recommended in February when we have a week of 75 deg F weather.  We would have been waiting about 2 months before mother nature would have taken care of that weed problem.  So here is some information about winter annual weeds and control.

The plant with the little tube shaped purple flowers that have been showing up turfgrass is called henbit. If you are not sure this is what you have, check the stems. If they are square rather than round, you have henbit. Square stems are an indication that it is in the mint family.  Henbit is a winter annual broadleaf with kidney shaped leaves, opposite arranged, with rounded teeth on the leaf margin.  The upper leave surround the stem.  It really likes disturbed, moist areas in turf and landscape beds.  Don’t get it mixed up with purple dead nettle or ground ivy, they are similar looking weeds. Most broadleaf weed herbicides are effective.

A plant that also is low growing but has round stems and tiny white flowers is chickweed. Chickweed is also a winter annual and starts to grow in the fall. They spend the winter as small plants and so most people do not pay much attention to them until they start to flower in the spring.

Remember, these are winter annuals that will die as soon as the weather turns hot. You can keep the turf mowed and you can let nature take its course. As you can see this year it got warm, then cold, then snowed, then warm again, dry and now 50’s – low 60’s and raining.  So waiting may not be an option for golf courses, parks, sports complexes, and lawns. We may need a jump start to get rid of those weeds.

Ok so here is a scenario.  We wait and let the warm weather kill off the winter annual weeds.  Now there is a void in the turf. What happens in voids in our turf as it warms up?  Crabgrass starts to germinate.  Hope you got your preemerge herbicide out for crabgrass!

Fall is obviously the best time to kill broadleaf weeds but these weeds will germinate throughout the Fall to Spring.  The majority germination in October but they will continue to germinate through the spring especially when we have those warm fall and winter days.  So a Fall application in November may not get complete control because more will germinate after that application.  Thats why a Spring application may be needed as well to clean up these weeds along with some dandelions that may have also survived.  Most broadleaf weed herbicides are effective especially ones that are three-four way mix.  FYI, at this time the weeds are more mature and harder to 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 www.facebook.com/KSUTurf

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

 

Homeowner Do-It-Yourself Lawn Calendar for Warm-Season Grass

(By Jared Hoyle, KSU Turfgrass Research and Extension)

Last week I got a lot of good feed back on the Homeowner Do-It-Yourself Lawn Calendar for Cool-Season Grasses so I decided that it would be good to go ahead and get the warm-season lawn calendar out there for everyone that is manageing zoysiagrass, bermudagrass or buffalograss.

The following is a lawn calendar for zoysiagrass and bermudagrass. Buffalograss, also a warm-season grass, but we will cover that separate because the management of buffalograss is a little different then zoysiagrass and bermudagrass.

Zoysiagrass and Bermduagrass Lawn Calendar

March
Spot treat broadleaf weeds if necessary. Treat on a day that is 50 degrees F or warmer. Rain or irrigation within 24 hours of application will reduce effectiveness.

April
Apply crabgrass preventer between April 1 and April 15, or apply preventer when the eastern redbud is in full bloom. This year we are getting a little warmer sooner but remember this cold snap that we just had would have killed any crabgrass if it had germinated. If using a product with prodiamine (Barricade), apply two weeks earlier. Crabgrass preventers must be watered in before they will start to work.

May – August 15
Fertilize with 1 lb. of nitrogen per 1,000 square feet per application. Follow the recommendations on the bag. More applications will give a deeper green color, but will increase mowing and may lead to thatch buildup with zoysiagrass. Bermudagrass can also have problems with thatch buildup but thatch is less likely with Bermuda than zoysia. Bermudagrass – Use two to four applications. Zoysiagrass – Use one to two applications. Too much nitrogen leads to thatch buildup.

One Application: Apply in June.
Two Applications: Apply May and July.
Three Applications: Apply May, June, and early August.
Four Applications: Apply May, June, July, and early August.

Remember to look and see if you are using a quick release nitrogen source or a slow release nitrogen source.  If you use a quick release source then it is immediately available but only lasts a couple weeks.  Thats why you would have to make a couple of applications like it is listed above.  If you are going to use a slow release source it will tell you on the bag how long the product will last.  Therefore, you might not have to make as many applications.

So generally you want to use a total of 2 to 4lb. of nitrogen per 1,000 square feet per year for bermudagrass and 1 to 2 lb. of nitrogen per 1,000 square feet per year for zoysiagrass.

June
If grubs have been a problem in the past, apply a product containing imidacloprid by mid July. Imidacloprid can be applied as early as mid May if there are problems with billbugs or May beetle grubs. These products kill the grubs before they cause damage. They are effective and safe but must be watered in before they become active. June is a good time to core aerate a warm-season lawn. Core aeration will help alleviate compaction, increase the rate of water infiltration, improve soil air exchange and help control thatch.


Late-July through August
If you see grub damage, apply a grub killer. If Imidacloprid has been applied, this should not be necessary. Grub killers must be watered in immediately.

Late October
Spray for broadleaf weeds if they are a problem. Treat on a day that is at least 50 degrees F. Rain or irrigation within 24 hours reduces effectiveness. Use the rates listed on the label for all products mentioned.

 

Buffalograss Lawn Calendar

Buffalograss has become more popular in recent years due to its reputation as a low-maintenance grass. Buffalograss does require less water and fertilizer than our other turfgrasses but often has problems competing with weeds in eastern Kansas. Remember, buffalograss is a low-maintenance lawn and not a “No”-maintenance lawn.

Buffalograss is an open growing grass that will not shade the soil as well as most of our other turfgrasses. Weeds are often the result. A regular mowing schedule can reduce broadleaf weed problems as most broadleaves cannot survive consistent mowing. Those that do either have a rosette growing pattern (dandelions, shepherds purse) or are “creepers” (henbit, chickweed, spurge). Annual grasses such as crabgrass or foxtail can also be a problem. A good weed preventer (prodiamine, pendimethalin or dithiopyr) may be needed prevent problems.


March

Spot treat broadleaf weeds if necessary. The most important treatment for broadleaf weeds should be in late October to early November well after the buffalograss is dormant. Treatments are much more effective then than in the spring as the weeds are smaller and the weeds are sending energy, as well as the herbicide, to the roots. Treatments in March are to take care of any “escapes” missed in the fall spraying. Spray early enough in March that the buffalograss is still dormant. Look at the base of the plants to make sure there is no green. Treat on a day that is 50 degrees F or warmer. Rain or irrigation within 24 hours of application will reduce effectiveness.  Use a combination product such as Trimec, Weed-B-Gon or Weed-Out. Weed Free Zone is also good and will give quicker results under cool conditions.

April

Apply crabgrass preventer between April 1 and April 15, or apply preventer when the eastern redbud is in full bloom. If using a product with prodiamine (Barricade), apply two weeks earlier.  Crabgrass preventers must be watered in before they will work. Avoid using broadleaf herbicides as the buffalograss is greening up as injury can result. The buffalograss will not be killed but growth will slow making the buffalograss less competitive with weeds.

June

Fertilize with 1 lb. of nitrogen per 1,000 square feet during June. More applications will give a deeper green color, but can encourage weeds. If it is felt that a second application is needed, apply in July.

If grubs have been a problem in the past, apply a product containing imidacloprid by mid July. Imidacloprid can be applied as early as mid May if there are problems with billbugs or May beetle grubs. These products kill the grubs before they cause damage. They are effective and safe but must be watered in before they become active. Again, I would only treat if grubs have been a problem in the past. Note that the whole area may not need to be treated. The beetles that lay the eggs for the grubs are attracted to lights and moist soil and those areas are most likely to be infested.

Late-July through August

If you see grub damage, apply a grub killer. If imidacloprid has been applied or if grubs have not been a problem in the past, this should not be necessary. Grub killers must be watered in immediately.

Late October to Early November

Spray for broadleaf weeds if they are a problem. Look carefully as our winter annuals such as chickweed and henbit are small and easily overlooked. Use a product that contains 2,4-D as it increases effectiveness on dandelions. Treat on a day that is at least 50 degrees F. Rain or irrigation within 24 hours reduces effectiveness. Use the rates listed on the label for all products mentioned.

It is as simple as that!  Enjoy!

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

Turfgrass Care for Homeowners on the K-State Radio Network

(By Jared Hoyle, KSU Turfgrass Research and Extension)

Just recently I was invited to speak with Eric Atkinson, host of Agriculture Today a daily program distributed to radio stations throughout the state. It features K-State agricultural specialists and other experts examining agricultural issues facing Kansas and the nation. I spoke with Eric about some issues that Kansas homeowners might be facing with their lawns and a couple things that homeowners shouldn’t worry about this year.

Click on the link below and hear more about;

  • possible winter injury
  • fertility
  • weed control
  • and more!

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

Preemergence Weed Control in Bentgrass Putting Greens

(By Jared Hoyle, KSU Turfgrass Research and Extension)

In the previous post about preemerge herbicides there is a table of many preemergence herbicides that available for professional turfgrass managers.  But when we start talking bout preemerge herbicides that we can use on bentgrass putting greens the list gets really short.  There are not many options out there for PREs on creeping bentgrass putting greens due to the injury they can cause to the putting surface.

Every golf course superintendent knows that one of the main priorities on the golf course is the putting greens. Therefore, weed control on the putting greens is a priority as well.  So lets just to go over some of the PREs that are labeled for creeping bentgrass putting greens and I will also mention one comment about each.

  • bensulide (Bensumec 4FL, Pre-San 12.5G, Weedgrass Preventer) – With this product you are not able to reseed for 4 months and do not use on greens that have more than 50% annual bluegrass.
  • bensulide +oxadiazon (goosegrass/crabgrass control) – To prevent injury apply two half rate treatments 10-14 days apart.
  • dithiopyr (Fertilizers w/ dithiopyr) – Older bentgrass varieties may result in undesirable injury.
  • siduron (Tuperson) – May be applied at time of seeding or to established creeping bentgrass for crabgrass control and bermudagrass suppression.

Also, you can see the list is a lot shorter then the list in the previous post but that is why managing bentgrass is so difficult.  Turfgrass managers must to do whatever they can to have a healthy growing creeping bentgrass system to prevent weeds coming in because once they are there, there isn’t many options to git ride of them.

Information in the previous list was acquired from “Turfgrass Weed Control for Professionals” by A. Patton and D. Weisenberger, Purdue University (and 11 collaborating states including Kansas). For more information about purchasing this publication see;

https://blogs.k-state.edu/turf/new-weed-control-publication-for-turfgrass-professionals/ 

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

“An ounce of prevention is worth a pound of cure.” by Benjamin Franklin – (That Goes for Preemergence Herbicides Too!)

(By Jared Hoyle, KSU Turfgrass Research and Extension)

“An ounce of prevention is worth a pound of cure” – Benjamin Franklin

When I start talking about pre-emergent herbicides this quote from Benjamin Franklin always pops in my head.  Although, Ben was giving fire-fighting advice to Philadelphians because fires were a dangerous threat at that time it does apply to many things we are dealing with right now, including spreading wild fires. (I won’t comment on that because I have no idea how to manage wild fires.) But I will talk about Pre-remergent herbicides.

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 (As we can see this year where it is getting warmer earlier!), 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 (and 11 collaborating states including Kansas). For more information about purchasing this publication see;

https://blogs.k-state.edu/turf/new-weed-control-publication-for-turfgrass-professionals/ 

 

***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

Knotweed – Last year it was April, Now its February!

(By Jared Hoyle, KSU Turfgrass Research and Extension)

Last year I did one of my first Turfgrass Selfie Series on knotweed control in April.  The knotweed had germinated and started to mature.  Just a couple weeks ago I was walking into my office and I saw knotweed already germinating.  (See picture below – Photo taken Feb. 22, 2017)

So needless to say.  If you didn’t get your preemerge out and you have a history of knotweed it is time to go out and attack the knotweed and other broadleaf weeds you have lingering around.  These weeds are easier to control now when they are young compared to when they get mature.

Below is the Knotweed Control Turfgrass Selfie Series Video I did last year but here are the take home messages;

  • Early germinating summer annual
  • Likes compacted soils/flooded areas
  • 2,4-D = fair control
  • 2,4-D + triclopyr or dicamba = excellent control
  • metsulfuron can be used in warm-season turf
  • PRE applications must be done in the Fall

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