Another Way to Stick it to Weeds

Tony Koski, Extension Turf Specialist

Since it was first introduced in 1974, Roundup (glyphosate) has always been sprayed on weeds. Because it is largely non-selective (will kill or harm any plant that is sprayed) in what it controls, using Roundup and its generic counterparts near desirable plants has to be done carefully to avoid unintended injury. The introduction of Roundup Precision Gel Weed and Grass Killer potentially makes it easier to apply glyphosate to individual weeds – without the concern of overspray, wind drift, and other application errors that could harm desirable plants. But a question we have, as with all new technology, is: does it work?

The application process reminds one of using a gel deodorant stick. A button on the bottom of the stick is clicked until the gel (containing a 1% concentration of glyphosate) is extruded through holes on the top of the stick. You then apply the gel by wiping the leaves of the weed. Sounds easy, right? What I

found, however, was that – to get a decent application of herbicide to a weed’s leaf surface – you have to support the leaf with your other hand while applying the gel. Of course, a rubber glove should be worn to avoid wiping your hand with the gel in the process. (Gloves should ALWAYS be worn when using any pesticides, whether natural/organic or synthetic types).

Because glyphosate is a systemic herbicide, complete leaf coverage isn’t essential to get good weed control. With the gel, you get streaks of gel on the leaf surface – which should be sufficient to control the weed. I tried this on some plantain growing in a groundcover bed outside of my office. The series of photos

shows the progressive death of the plantain. While plantain is admittedly one of the easiest landscape weeds to kill, the Roundup Gel worked well on this weed. For those of you expecting “instant gratification” weed control, you will have to be patient with this product. In the case of this plantain, it took about 16 days from application to death. I will next test this on quackgrass growing in juniper beds and perennial beds, which could be an excellent use for this product.

Roundup Gel applied on 23 June

Injury appears the next day thanks to the pelargonic acid that is also in the
gel stick; complete leaf coverage (I did try!) would have burned the leaves
down more quickly.

Complete death is achieved after about 2 weeks

Hort Peeves: When you have to pray after you spray

Posted by: Alison O'Connor, Larimer County Extension

Though she will yell at me for posting this, I'm going to use my mom as an example of this hort peeve. Sorry mom...

When talking to mom a few weeks ago, she asked me, "Hey Al. I want to kill some weeds in my lawn. What do I use?" I advised her that a lawn weed control product is best (after talking about why the weeds were in the lawn). There was a pause and then she said, "Shoot. I used the wrong thing." When pressed, she admitted she used glyphosate (Roundup). And then with a bit of panic in her voice, "Did I kill the lawn?"

One thing that should be noted is that she asked me after she sprayed and not before. Mom!

No, this is not my mom's lawn. This was in Broomfield, Colo.

But I would hazard a guess that most of us have been in this situation before, thus praying after spraying. I have.

Here's your advice for the day: Read the label first. Then think about the product and what the label says. And then read the label again if you have questions. And if you're still unsure, contact the company that makes the product or call your local Extension office. It's very hard to un-do chemical damage. Fellow hortie, Curtis Utley, recently blogged about types of herbicides and their damage.

For some reason, once I started looking for chemical damage in landscapes...especially "Oops I used Roundup", it wasn't hard to find. Lawns are probably the easiest thing to spot.

As seen in Loveland; likely glyphosate damage.

Whatever your opinion is on Roundup, it is commonly used (and misused) in landscapes by professionals and homeowners. So what can you do if you accidentally use the wrong product in the wrong place? Well, it depends on the chemical. If it's just glyphosate and you just sprayed it, try to wash it off. If the product has dried on leaf tissue, like the lawn, you can mow the lawn to about an inch to remove the foliage. BUT not all Roundup is the same (refer to Tony Koski's blog on this). If you used one of the extended control products that contains imazapic or imazapyr, watering can make things worse.

Mistakes can be made and sometimes the damage is significant and costly. So be smart, read the label and think...it can save you a lot of angst. And prayer.

As seen in Wellington, Colo.; a misapplication of a broadleaf herbicide at a park.

Got weeds? Aerial application is not recommended in the big city

By Curtis Utley, Jefferson County Extension

With the fantastic moisture we have received along the Front Range this spring homeowners are seeing weed growth exploding and with cool temperatures many, myself included, have not been puttsing around in the yard pulling the wayward weeds as frequently as in years past. If you are considering tackling your over-gown weeds with chemical herbicides be aware of a few possible pitfalls and read the entire label before purchasing an herbicide and making an application. Label information is provided to consumers to protect you, your yard and the environment. There are selective herbicides that will kill broadleaf weeds growing in your lawn without killing your grass. There are also selective herbicides that can kill the grass growing in your flower or perennial beds without killing your flowers. There are also non-selective herbicides that will kill anything green, and lastly, preemergent herbicides prevent seedling establishment.

Phenoxy herbicide damage to a perennial bed due to over-spray 

The most commonly available weed killers sold to consumers are the phenoxy herbicides.  Common phenoxy herbicides include: 2,4-D, Dicamba, mecoprop-p (MCPP), and MCPA. Phenoxy herbicides are selective herbicides that kill broad-leafed dicotyledonous plants and do not harm grasses and other monocots. Phenoxy herbicides are auxin mimics and cause hormonal changes leading to rapid uncontrolled growth leading to the death of susceptible plants. The herbicide targets the growing points where cell division is rapid. The symptoms of phenoxy herbicide damage include, twisting, curling and rolling of leaf and stem tissues.  A few weed control products containing the auxin mimics are sold  as hose-end products or are permitted to be applied in an aftermarket hose-end sprayer. While this application method is simple and fast I strongly caution against applying herbicides through such a device due to the potential for overspray. Hose-end sprayers can produce variable droplet sizes which can allow for particle drift resulting in unintended consequences. The other potential issue with hose-end sprayer applications is 2,4-D volatilization. If you apply a broadcast application of 2,4-D on a day when temperatures climb above 85 degrees F. the herbicide can become a gas and float on air currents damaging trees and shrubs.

Phenoxy herbicide injury to green ash due to 2,4-D volatilization

Phenoxy herbicide injury to red oak due to 2,4-D volatilization

Herbicide applications are best accomplished by spot spraying individual weeds with a pump up sprayer. You will use less product, saving money, and can safely direct the application to weed leaves. Spot spraying and adjusting your spray nozzle to produce a course spray pattern greatly reduces the risk of over-spray, herbicide drift and volatilization. 

Dandelion dying after a spot spray application of 2,4-D

Sins of the Landscape

My fellow Horticulture Agents will agree; sometimes it is hard to drive around town and see the landscape “sins” that are going on.  One of our Tri River Area Master Gardeners recently wrote an article on trees.  It pained her to see them improperly planted, pruned or ignored.  Please do your homework.  Plant the right tree in the right place.  www.ext.colostate.edu/mg/Gardennotes/632.html

Plant using the latest updated planting techniques.  www.ext.colostate.edu/mg/Gardennotes/636.html

Do your homework before you prune.  www.ext.colostate.edu/mg/Gardennotes/613.html

If the tree is in the right place, you should have minimal pruning to do.  Always remove dead, dying and disease wood as soon as you see it.  And please never, never top a tree.  Some people will say they are pollarding.  Pollarding is started on saplings and was used in Europe to produce a quick large amount of wood that was then used for firewood.  “Pollarding”, aka topping, should never be done on large trees.  When topping is done, it is committing the tree to a short life.  Talk to your local Masters Gardeners about trees.  They will be happy to fill you in so you can grow trees that live longer than we do.  Leave a Legacy.

Right plant, right place

Now on to the next “sin” I witnessed driving home the other night.  A local business was laying weed fabric.  Well, the big problem with this is they were laying it over already existing fabric and decomposed granite rock.  Then they were putting a 1” or larger river rock on top.  I assume they were doing this to help conquer the weeds.  The problem, actually there is more than one, is first: old fabric gets dirt built up on it and it essentially clogs the pores of the fabric.  This dirt build up on top is why the weeds are now there.  Secondly, one has to understand the movement of water through different materials.  Water moves through one material before it will start to penetrate another layer.  These layers are called interfaces.  So by the time water moves through 4 layers of material how much is going to actually get to the soil below and to the roots of the plant.  The correct thing to do would be to remove the existing rock mulch and fabric and start over.  Or not use fabric to start with and use other methods to control weeds.

Dandelion photo by Susan Carter

Controlling weeds starts by identifying the weeds that you are trying to get rid of.  http://www.ext.colostate.edu/sam/weeds.html We have winter annual weeds that start growing in late summer or early fall.  These them start growing like mad in early spring and are already setting seed at lower elevations.  Downey Brome, aka Cheatgrass, is one great example of a winter annual.  Then we have annuals that germinate in spring or summer.  Biennials type of weeds grow vegetation one year and bloom and go to seed the second year.  And perennial weeds are ones that will come up at least 2 years or more from the root system.  Woody weeds fit in this category.  Pre-emergents can be used to control weeds in areas like the rock mulch bed in my story, but it is important to know the identity of the weed or its life cycle so you apply the herbicide at the appropriate time.  Of course, manual removal of the weeds is one way to control them.  Spraying herbicide on them after they have germinated is another and trying to out compete them with properly grown turfgrass or cover crops is another. (Always read the label and follow instructions on pesticide labels.)

Feel free to take weed samples to your local Extension office.  Please bring the entire plant and if it is blooming, that is even better.  The more information we have, the better we can help you.  So do your homework, choose what works best for you and your landscape, to help you maintain a healthy landscape.   Blog posted by Susan L Carter, Horticulture Agent, CSU Extension Tri River Area

Roundup is Roundup…Right?

Tony Koski, Extension Turf Specialist

Which one do I use? They both say  Roundup!

If you are reading this in hopes that the turf specialist has seen the light and jumped on the Occupy Monsanto bandwagon, well…you can stop reading now. Glyphosate/Roundup is still, in my opinion, one of the most effective, inexpensive, easy-to-use and safest herbicides available to the home gardener – and to professional weed managers as well. But a stroll through the pesticide aisle of any hardware store or big box garden center can present to even the sharpest of gardeners a somewhat bewildering selection of Roundup products from which to choose…Roundup Concentrate…Roundup Concentrate Plus…Roundup Extended Control. The various Roundups entice you with promises like “Results in 12 hours” (faster is always better…right?) or “Controls weeds for up to 4 months” (longer is always better…right?). And then there is yet another glyphosate-containing product, ominously named GroundClear, which provides one year or more of weed control (REALLY longer is BEST…right?). It’s easy to understand the confusion when asking oneself “Which one do I buy?”. And I suppose it’s somewhat easy to understand when consumers (professional applicators don’t get a break here) misuse these products in the landscape – although a thorough reading of the label would, in most cases, prevent some damn dumb mistakes. (What? Read a label? Ain’t nobody got time for that!). Sooo….how different are these Roundup products? Can they be used interchangeably? Is one better than the others? Are all of them “safe” for home landscapes?

First, the traditional verbiage – to protect my you know what – whenever we Extension types write about pesticides: READ THE LABEL before purchasing, much less using, any of these products! A reading of the ingredients section of the various Roundup products demonstrates that they aren’t the same. And while the "where to use/not to use" instructions aren’t always the most clearly written, a close reading (ok, maybe 2 or 3 times…) of the label will help prevent misuse of these products. 

Roundup Super Concentrate (white bottle…purple cap) is your good ol’ pure and simple glyphosate.  Use it wherever (wherever the label allows, that is…yes, READ THE LABEL!) you need non-selective control of weeds in your landscape. It is taken up only by leaves and other above-ground green plant tissue. No soil residual. No root uptake. No extended control.  This Roundup can be safely used: on your driveway or sidewalk or patio…on mulch circles around trees (but don’t spray the trunk, or surface roots, or suckers)…to renovate your lawn…or to kill a section of your lawn and replace it with a flowerbed or veggie garden. This is the slowest acting Roundup product, taking anywhere from 5-10 days before you begin seeing symptoms that the weeds are dying. But because we are so impatient (we “need” FASTER internet… FAST food…RAPID transit…INSTANT mashed potatoes), a couple of other Roundup products were developed to satisfy consumer demand for more rapid weed kill. Enter Roundup Plus…

Faster Roundup is better....isn't it?

Roundup Concentrate Plus (white bottle…red cap) contains glyphosate and another herbicide called diquat dibromide. The diquat is added to give a more rapid burndown of weeds that have been sprayed. Other than providing the more rapid (within about 12 hours during hot weather) visual symptoms that the weeds have been sprayed, this Roundup product works the same way as the basic concentrate. All foliar absorption, no root uptake or soil residual. No extended control. 

Roundup Ready-to-Use Plus (blue and white bottle) contains glyphosate and pelargonic acid. The pelargonic acid makes this Roundup product work even more quickly than the Roundup Concentrate Plus – you may see wilting within 3 hours on a hot, sunny day. So, for the VERY impatient, this Roundup product works even more quickly than the Concentrate Plus product – but is otherwise the same: all foliar uptake, no root uptake, no soil residual, no extended control. Use it the same way you would the above two Roundup products.

Roundup Extended Control (gray bottle) contains pelargonic acid (for rapid burn down) and a herbicide called imazapic. Imazapic is added to provide the “extended control”. It works as a preemergence herbicide to provide 3-4 months of weed control by killing germinating seeds/seedling weeds. However, imazapic also is somewhat root active and can provide postemergence control of some weeds as well. This is where things get tricky. Imazapic is fairly water soluble, so it can move in soil. This means it can move to parts of the landscape where you haven’t sprayed it (down slopes, for example…or when sprayed on gravel-covered plastic). And because of the long soil residual, don’t use this product where you may want to plant something in the near future (so this one is a no-no for lawn renovation, nor should it be used where you plan to plant a veggie or flower garden in the future…or trees or shrubs).  The label does allow use over the root zone of trees and shrubs (established ones…not newly planted), including on mulch circles around trees. However, imazapic has been shown to cause injury to a

few tree species which are sensitive to it: lindens, green ash, and cherry trees. Soooo….while it is generally safe to use in those parts of the landscape where you need control of existing weeds AND desire some long term weed control/prevention, you have to recognize the potential for this stuff to “move” in the landscape. Use the same precautions that you would with any Roundup product…and maybe consider if you REALLY need to use this over the root zone of your trees? 

And then there is GroundClear….While it doesn’t have Roundup prominently displayed on the label, this is another Roundup product. It is aggressively marketed on the radio and in the aisles of big box stores. Who wouldn’t want weed control for a year - or longer? This is the one where the “Keep out of reach of children” line on the label maybe should read “Keep out of reach of adults who don’t read a label”. This Roundup product contains imazapyr (a close relative of imazapic…see above), which is a VERY long-lasting, soil/root-active herbicide. Imazapyr can last a year or longer in soil, depending on soil type and how much moisture the soil receives. It is non-selective, can move with water in soil, and is easily taken up by roots of trees (yours or your neighbor’s), shrubs, vines, flowers, veggie plants, turf….you get the idea. As the name would imply, this product really does “clear the ground” on which it is applied. In my opinion, there are few places in a home landscape where this product could be safely used. I doubt that there is a driveway, patio, or fence line in any urban landscape that doesn’t have a tree or shrub root growing under it. Unfortunately, the promise of long-term weed control is so irresistible, it is bought and used in places where there is significant potential for damage to trees and other desirable landscape plants. This is one that you want to avoid using in your landscape, unless you REALLY, REALLY know what you are doing – and even then I would be hesitant to use it.  I have visited landscapes where professional applicators (who should know better…and who violated the label by using it where they shouldn’t have) have killed or injured dozens of trees using this and similar products for mulch circle weed control.

Trees killed by improper use of herbicide
containing imazapyr.

Like most things in life - when preventible, bad things happen - you can only blame yourself for not reading (or following) instructions and heeding warnings.  When you purchase any pesticide, you enter into a legal agreement that you will use it as the label instructs. Your trees and turf can’t read the label…they trust that you will.