Title: Weeds AR Wild, Ep. 01: 2021 Burndown Applications and Ryegrass Control (03-02-21)

Arkansas Row Crops Radio, providing up-to-date information and timely recommendations on row crop production in Arkansas.

Tommy Butts: Welcome to the Weeds AR Wild podcast series as a part of Arkansas Row Crops Radio.
 
My name is Tommy Butts, Extension Weed Scientist for the University of Arkansas System Division of Agriculture. Thank you for joining me today for the first ever episode of Weeds are Wild podcast series.

Today weÕre going to be discussing burndown herbicide options & more specifically in details, ryegrass management ahead of most of our cropping systems in the state of Arkansas. 

The first thing I wanted to mention is itÕs really good news to see our temperature starting to climb back up after that week or even longer of cold temperatures, snow, ice, all of that kind of stuff. Our temperatures coming back up into the 55 & 60Õs is really critical for us to get an effective kill out of our herbicides & burndown herbicides. Now I say all that & IÕm looking out my window currently & I see frost on the ground, which is not a great sign. But our forecast looks really promising over the next few weeks, climbing like I mentioned to about 55 degrees into 60 degrees for highs everyday. Those temperatures, especially for sustained periods of time like the week or two weeks weÕre going to have are really critical to make sure we can get enough effective kill. We need those weeds to be actively growing. When theyÕre actively growing they can absorb those herbicides into the systems. Specifically like systemic herbicides like Roundup & 2-4D, & really give us a complete kill as those herbicides will translocate throughout the plant. Now even contact burners like Paraquat really like to have a  little more heat as well to really burn down that vegetation, so these temperatures are really going to be critical to make sure our burndown herbicides are as effective as possible. 

Now one of the first things I wanted to talk about, because we get a lot of calls on these, are winter annual broadleaves, or winter annual broadleaf junk I like to call it. This is a range of different weeds that can emerge. Henbit, mayweed, vetches, buttercup. ThereÕs all kinds of different winter annual broadleaves that kind of pop up out there across the landscape. One of the first things that I always like to recommend for most of those weeds are a tank mix of 2-4D & glyphosate or 2-4D & Roundup. That combination is very effective at controlling most of these winter annual broadleaves & itÕs a really economical mix for a burndown application. So itÕs a benefit on both sides because it takes care of a wide spectrum of these broadleaf weeds, as well as being very economical for our growers out there. I will say that mix specifically is really a best option if we are in a conventional tillage system & we have another spring tillage event thatÕs going to be coming down the line here before we plant, because that 2-4D & Roundup can get into those plants, be working internally & even if they donÕt completely 100% kill those weeds, they should damage them up pretty good & then our spring tillage event can come in & completely finally finish off any of those weeds that are there. 

I will also mention Paraquat may be a good option in certain situations. One of those situations thatÕs been popping up that both Dr. Tom Barber & I have received some pictures & phone calls on is common groundsel & weÕve had reports that Roundup & Paraquat, IÕm sorry, Roundup & 2-4D & glyphosate just arenÕt being able to control that weed effectively. So we might need a burndown, a burner option such as Paraquat to really effectively get rid of common groundsel out there. So again, in certain situations Paraquat may be a good option for controlling some of these winter annual broadleaves as well. 

I mention that for a conventional tillage system. If you happen to be in a reduced tillage system or no tillage system, something where maybe you are only going out to re-hip beds, & thatÕs the only kind of tillage event that youÕre going to have out there, you really might want to consider adding residual product in the tank as well, like Valor. That may be a little dependent on weed concerns & how far out your planting is & those kinds of things, but adding in that residual product, especially in these reduced tillage situations, can help make sure we donÕt have any more flushes emerge of winter annual weeds. It also can help with some of those early summer annual flushes & help control those, & help us basically start clean when we do plant. We donÕt have any vegetation emerge at the time of planting.

Valor is pretty much primarily a broadleaf material so it wonÕt help on a lot of grasses, but a lot of the broadleaf junk that we get concerned about, Valor can help give us that residual & help us start clean before we plant. 

Now the one concern with adding in Valor into a mix is that we do have to watch our plant back. For Valor for most crops is a 30 day plant back. So just be aware of that if we are adding that into the tank to watch that plant back interval for the cropping system that we plan on putting on that ground. 

Jumping into the ryegrass situation where I want to get into a little more detail. Resistance concerns for ryegrass across the state are continually increasing & by far the #1 phone call we get for spring burn downs is trying to manage ryegrass. ItÕs definitely our #1 burn down weed we need to be concerned with. ALS inhibitor resistance is really thought to be widespread across the state. The last time a resistance screening survey was conducted on ryegrass in 2012 showed about 60 or more percent of the populations that were screened, came back as ALS inhibitor resistant. However both Tom & I have gotten some reports that in some areas ALS inhibitors have actually been working quite well in addition to Roundup. IÕm not saying thatÕs the case all over the place, & if you know you have ALS resistance, itÕs definitely not an option, but in certain situations where we first suspected that we had ALS inhibitor resistance, something like Leadoff plus glyphosate has actually been showing to have some pretty good activity on ryegrass in this area. So that may be an option. Now like I mentioned Leadoff, that is going into corn because there is a pretty good plant back interval there, so be aware of that. That may be an option to try & help manage ryegrass in certain situations across the state. 

I mentioned glyphosate or Roundup, that also can be an option in some areas, but again, weÕve had a lot of reports of glyphosate resistance across the state, especially in south Arkansas, itÕs very widespread, but it has increased north of I-40 & weÕve had several reports of glyphosate resistant ryegrass in Northeast Arkansas as well. So definitely glyphosate is becoming a limited option for our ryegrass management across the state of Arkansas as well. 

That gets us down to clethodim which can be a very beneficial option for trying to successfully manage our ryegrass. There are some severe resistance concerns again in south Arkansas for clethodim resistant ryegrass. Especially because right across the river in Mississippi thereÕs several counties that have confirmed clethodim resistant right across the river there. So there is some major concern for some clethodim resistance, especially in south Arkansas, as well as I have had numerous phone calls about the 30 day plant back to our corn & rice crops. With us already reaching the beginning of March here that plant back interval is very tough to adhere to effectively ahead of those crops. ThatÕs a challenge when weÕre trying to use clethodim to effectively control our ryegrass. 

So with all the resistance concerns & potential plant back issues & things like that, we really get down to one option & that happens to be Paraquat, which may be our only option in some of these situations. I will mention that with Paraquat, although it is effective on ryegrass, a lot of the times you probably need to expect that itÕs going to take two shots to effectively kill out that ryegrass completely. We really want to plan on probably having an application of Paraquat now & then 2-3 weeks right at the time of planting, whatever our crop is, we want to make sure to throw out that 2nd shot of Paraquat to really kind of finish off most of that ryegrass that may be up. We also have the capability to add a photo system II to our PSII inhibitor into our Paraquat mix & that greatly enhances the effectiveness of Paraquat. Things like metribuzin ahead of soybeans, diuron ahead of cotton, Atrazine ahead of corn. Those PSIIÕs mixed with Paraquat will greatly enhance the activity of that on our ryegrass & help kill out that weed species as well, even more that Paraquat by itself. 

I mentioned the importance of getting this ryegrass killed out before the crop is up, simply because, especially in things like row rice or corn, once that ryegrass is up, thereÕs really no option post emergence in those crops to effectively control this. Especially if we have glyphosate & ALS resistance varieties of ryegrass or sub species of ryegrass out there, we really donÕt have an option in corn & row rice anymore to try & kill that post, so we need to get it under control ahead of crop emergence, otherwise itÕs going to be there the rest of the season competing with our crop. 

For more details on resistance & management of Italian ryegrass, make sure to go online & download our fact sheet 2191 Management of Italian Ryegrass & Agronomic Crops. We go into a lot more detail in the fact sheet on management & resistance & all those types of things, so itÕs a great resource to have if youÕre concerned about Italian ryegrass in your area. 

So with that I just wanted to hit on a few final overall reminders. One of the first things that I want to mention is to make sure that our temperatures are warm enough for an extended period of time, which or forecast really looks promising. It looks like weÕre on the right path there. 

The next thing, you really need to know what weeds you have out there & what resistances you might have so that we can appropriately select our herbicides. So itÕs really critical to get a weed ID, or also again, know if you have glyphosate & ALS resistance or if you have clethodim resistance, or those kinds of things. Make sure youÕre aware of those so we can appropriately select herbicides & save ourselves from having to make multiple applications just because a failed attempt as we selected the wrong herbicides for our situation. 

I also mentioned some other herbicides like Valor or Leadoff or clethodim that have plant back intervals to a lot of our cropping systems. So make sure to pay attention to those plant back intervals & maybe download or get a copy of the MP 519 that we have out there & the row crop plant back intervals for common herbicides, so make sure we can watch that & we can reduce our chances of crop injury as a result of some of these burndown applications.

And finally I wanted to mention, if youÕre relying of Paraquat, expect to make 2 applications with that. Especially for ryegrass control. We want to have one early, about this timing, & want to make sure to come back with that 2nd Paraquat application to finish everything off right at the time of planting. We can mix that with our residual herbicides that we are planning on spraying pre-emergence anyway & we have that burn down plus our residuals going out, so we can finish off our ryegrass & then start right away with our residuals into our cropping system for the year. 

Thank you for listening today & joining us for this first ever episode of the Weeds are Wild Podcast. If you ever have any questions please feel free to get ahold of me. Please join us next week for the 2nd episode of the Weeds AR Wild Podcast. Dr. Tom Barber will be discussing some different herbicide resistant concerns across the landscape. 

So thanks for joining us for the Weeds AR Wild episode podcast series on Arkansas Row Crops Radio.

End notes: Arkansas Row Crops Radio is a production of the University of Arkansas System Division of Agriculture. For more information please contact your local county extension agent or visit uaex.edu