Title: Weeds AR Wild, Ep. 04: Rice Weed Control Programs for 2021 (3/24/21)

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 AR Row Crops Radio. My name is Tommy Butts, Extension Weed Scientist for the University of Arkansas System Division of Agriculture. I have the privilege of being your host this week for the 4th episode of the Weeds AR Wild podcast series. This week we'll be discussing rice weed control strategies & programs for the 2021 growing season.

The first thing I want to mention is that every one of our herbicide programs needs to be setup for barnyardgrass first. That is by far our #1 most problematic weed. We conducted a rice weed management survey this past fall & it was overwhelming how many people voted barnyardgrass as our #1 most problematic weed across our rice acres. Along with that survey we also asked then to estimate yield loss based on barnyardgrass across the state & respondents indicated that they estimated an average loss of nearly 15 bushels per acre of yield across our Arkansas rice fields strictly due to just barnyardgrass populations out there. So that makes that a very, very problematic weed for us across the state in our rice crop. 

Now the best thing that I can tell you for managing our barnyardgrass populations out there is to use residuals. And use multiple effective residuals in every application that goes out. That's critical. That is our underlying main thing that we need to do is use multiple effective residual herbicides & overlap those residuals to get the best barnyardgrass control. Just never let it get out of the ground.

Now there's multiple different residual products that we can use & combinations of those products that will maybe work in your operation. But a few things that have worked really well for us is obviously starting off with a foundation of Command. Command continues to be one of our best herbicides from a residual standpoint for grass control & it also has a little resistance out there, so it's still very effective across broad parts of the state which is really good. 

Now with Command we want to select a rate that can be effective based on our soil types. And what I would tell you is that a little bit of bleaching on our rice crop is actually a good thing. Now we don't want to turn our rice completely white. Definitely not. But if we see a little bit of a white flash on our rice, that lets us know that Command is activated, it's working & it's giving us barnyardgrass control as well. So we kind of want to select that rate where we get a tiny bit of flash on our rice, but not so much that we completely bleach the entire rice crop.

Now mixing with that Command like I mentioned, we want to have multiple effective modes of action in there. One of the best herbicides that has worked well for us from a residual standpoint in small plot research continually year in & year out is Quinclorac or Facet. Doing Command plus Facet mix upfront continually gives us some of the best weed control that we have in our research plus Even if we have Quinclorac or Facet resistant barnyardgrass from a residual standpoint we'll still get activity out of it & so I would really like to recommend moving that Facet up, using it as a pre-emergence product rather than trying to save it as a post-emergence product later on in the season. 

Now if we're in a Clearfield or FullPage system, Command plus Newpath or Preface can also be a good option & give us barnyardgrass control as long as we don't have resistance developed, but those can be, again, multiple effective modes of action, both working on that barnyardgrass. And give us a little bit broader spectrum weed control as well. 

Now one of the other things I want to mention is, in our plots across 4 different site years, the tank mix of Command, Bolero & League. So those 3 herbicides applied delayed pre, has been literally the cleanest mix across my small plots that I've used the past couple of years & across multiple sites. Now I realize that mix is extremely expensive but that again, that tank mix has been extremely clean & as a result it has saved me at least one, if not two post-emergence applications on the backend, which then resulted in overall, more economical herbicide program cost. So even though I spent a lot more upfront there, because it saved me on the backend, I ended up saving my overall herbicide cost. Now I will say, I would not recommend that broad spectrum across all our acres, but if you've got a problematic field & you're  looking for something new to try, this 3-way tank mix may be worth a shot just to see what kind of barnyardgrass control you can get out of it, because as I mentioned it has worked really well for us in small plot research.

Now as well that tank mix with Bolero & League in there also gives us some sedge control materials & some broadleaf control materials, so it's really good on a whole broad spectrum of weed species that we may have out there in our rice crop. 

Now following that first initial residual application, we want to come back & overlap our second level of residuals about 14-21 days after that first application. Now on this second application of residuals there's a whole range again of combinations or different products that we can use. Prowl & Bolero is a good mix to throw out at this time with different modes of action there to get us effective control on barnyardgrass. Again we can do maybe a sequential shot of Command, depending on or soil type & again mixing maybe Command & Bolero or Command & Prowl like a RiceOne. Again maybe do another shot of Command & Newpath or Preface. There's a whole lot of options here that we can throw in that second overlapping residual shot to give us multiple effective modes of action again & really make sure that we extend our residual control of barnyardgrass & not let it get out of the ground.

Now the reason I stress residuals so much here, is again based on our survey this past fall. One of the questions we asked was how often is barnyardgrass missed with the first post-emergence application. And respondents indicated about half the time that their barnyardgrass populations were missed with the first post application. So half the time we're missing our barnyardgrass with our first POST shot, it's just thrown out the window. The next question we asked on the survey was ok, if that first POST application fails, how many more applications does it take to successfully get that barnyardgrass under control. And overwhelmingly the respondents indicated that it takes about three more POST applications following that failed first application. That's huge. That means we just had to use four different postemergence applications to try successfully to control that barnyardgrass that we missed. So as I said those residuals are extremely critical so we can get it under control early, we don't let it out of the ground & then we don't have to rely as heavily on those postemergence applications for complete control, because otherwise if we miss, we really miss badly out there & we have a lot more of those POST applications to get it under control. 

So I say all that. After we get through those two residual applications, those overlapping residuals, that third application, we should be hopefully getting to our pre-flood timing. Those first two overlapping residual applications should be getting us through the season enough to get us to that pre-flood timing & once we're there, we really can pick & choose our herbicides based on what weeds have emerged at that pre-flood timing. So as opposed to just kind of selecting herbicides at a whim we can really scout & specifically pick out the herbicide that will take care of whatever weeds we now have at that pre-flood timing to keep us clean & head out into flood. So for example if we have more barnyardgrass emerging is a time we need to use a Clincher or Ricestar shot. Do we have broadleaves like coffeebean or jointvech coming up? Do we have sedges out there, like flatsedges, yellow nutsedges, that kind of stuff, weedy rice. What's coming up now at this time that we need to specifically select an appropriate herbicide that will take care of those weeds specifically. That's what that third application at that pre-flood timing really should aim for. Now as a part of that we really need to know our resistances. If we don't know our resistances, & we're just going out there spraying herbicides that barnyardgrass or weedy rice or any of those other weeds are resistant to, we are just throwing money down a drain, because we are using a herbicide that's not effective & it's not going to give us the control that we need. So we really need to know the resistances out there as well before we select an appropriate herbicide for that POST application. So basically we need to know what weeds are out there & know what resistances we have in those weeds so we can effectively select that postemergence herbicide & get the most bang for our buck. 

Now I do also really want to mention quickly, if you know that you have Newpath resistant barnyardgrass or weedy rice, switching to the FullPage system is not going to help you manage those weeds successfully. If you have Newpath resistance, Preface is the same thing as Newpath. Postscript is the exact same thing as Beyond. The FullPage system does not give us any better weed control or it doesn't improve control if we already have resistance out there compared to the Clearfield system. The FullPage system is really based on the tolerance of our rice so that we don't see injury in our rice crop. Once again if we know we have Newpath resistance, the FullPage system is not going to help us get any better weed control in  that situation. 

Now jumping out of barnyardgrass, we've named a lot of different programs there for successfully controlling barnyardgrass. I want to mention a few other problematic weeds. Weedy rice continues to be one of our main problematic weeds out there. It was normally about our #3 listed most problematic weed in our survey. Bolero can help slightly in certain situations out there. Specifically if we're in water seeded rice & we can use a pinpoint flooding method, Bolero can be pretty effective at managing our weedy rice populations. Otherwise the old standby of Clearfield or FullPage systems are really beneficial still at controlling a lot of our weedy rice populations out there. Using the Newpath or Preface & then following it up with Postscript or Beyond, depending on what system you're in. But we do have a lot of resistance in our weedy rice populations out there as well, so that is becoming more challenging every year. 

One new product that we have available this year through a section 18 is Rogue. It's a HPPD inhibiting herbicide so a bleaching herbicide. Section 18, if you have a water seeded field that's on a zero grade. You could talk to Gowan & this herbicide may be an option to provide some weedy rice control for you out there this year. Otherwise if we're in really bad weedy rice areas & know we already have the ALS resistance in that weedy rice, you really need to consider switching to the Provisia system or down the road here, Rice Tec is developing their Max Ace system that will hopefully be available in upcoming seasons & we really need to switch to those systems to give us a different set of herbicides or modes of action that we can use on that weedy rice, because otherwise we're really limited in options that can successfully control that weed in our rice crop.

Now the next problematic weed that I've gotten a lot of calls on & it actually was our #2 problematic weed in our survey are sedges. Sharpen & Bolero upfront are normally our best residual flatsedge materials, so rice flatsedge, small-flower umbrella sedge, the new white margined flatsedge that's out & about. Those are probably our two best materials. Facet or Quinclorac can also help certain situations. And I say all of this because most of our flatsedge populations across the state are considered to be ALS inhibitor resistant, so I tend to just avoid those in my recommendations & rely on the Sharpen, Bolero or Facets to help us from a residual standpoint on those. 

From a POST standpoint, Basagran plus Propanil or Loyant continues to be our best postemergence option for flatsedges. And with Loyant, we can reduce the rate to 8 fl oz per acre if those sedges are less than 6 inches tall. So we can use a little bit lower of a rate & it's still really effective at controlling flatsedges or small-flower umbrella sedge. 

Finally for yellow nutsedge, because that's a little bit different as far as the sedge species go, we really need to rely on our ALS inhibitors there, so Permit, Permit Plus & Gambit are really our best options when it comes to managing yellow nutsedge. So if we develop ALS resistance, yellow nutsedge becomes very challenging because we just don't have a good second option there. It normally takes sequential POST applications to knock it out of different herbicides, if that's the case where we have less resistance. But luckily that's not wide spread yet, so Permit, Permit Plus, Gambit are our best options there for that weed. 

Now with that if we do have other problematic weeds out there, at this time check our MP 44 for some of our recommendations. Try & use some of the different products that maybe are broad spectrum weed control killers like a Propanil covers a broad spectrum of weed species. Some of the ALS inhibitors can cover broad spectrum weeds. Those can be very beneficial. And as always please feel free to give me a call anytime you have questions or you're looking for a better recommendation & those types of things. Just give me a call & we can chat about your situation. 

Just to kind of get to my last couple of things real quick as far as row rice goes, we're going to have a separate podcast later on in the season, but I did want to mention that from a residual standpoint on row rice, timing becomes really critical & we want to make sure that our residuals are overlapped at 14 days, not 21. Some research from Dr. Tom Barber has shown that if we stretch that residual overlap from 14 to 21 days, that we have a significant reduction in control so we really need to overlap those residuals 14 days apart, otherwise we will see a significant loss of control of row rice fields out there. 

So finally the last thing I want to hit on is just some general recommendations for weed control across the board & Dr. Tom Barber hit on a few of these a couple of weeks ago in his resistance talk, specifically on glufosinate-resistant pigweed, but these strategies can be applied across the board in cropping systems and weed spectrums, so I kind of wanted to mention them again. I have it broken down with an easy memory aid known as SPORTS. So if you can remember SPORTS, this can really help you out a lot with your with your weed control strategies moving forward. S stands for start clean. We want to make sure we don't have any weeds emerge at the time of planting. P is pre-emergence herbicides. We need to get those herbicides out. Don't let those weeds ever get out of the ground to start with. O is overlapping residuals. So make sure that we overlap those residuals. Make sure again that we are not letting weeds get out of the ground & extend that period of time where we can be weed free. R is required integrated weed management tactics. So make sure we are implementing diverse strategies. Trying to use a pinpoint flood. Manage the weed seed bank. Getting our flood on maybe a little bit earlier so we can have that cultural strategy use. Those types of things can be extremely beneficial for managing our weeds & delaying out the evolution of resistance. T stands for timely. We need to be timely with all of our applications & weed control strategies, whether it's making sure we get those residuals out in time or applying our POST products when weeds are small. That's very critical. And then our final S is selection. And by selection, what I mean is we need to select appropriate & multiple effective herbicides for our situations whether that's the residuals, the POST products, those types of things. We need to make that selection of herbicides really critical to get the most bang for our buck as well. So again, SPORTS, if we can remember that analogy that will really help us throughout our entire weed management process for the 2021 growing season.

So with that I just want to say thank you for listening today. Please tune in next week for Dr. Tom Barber. He will be discussing corn pre-emergence herbicides & programs for the 2021 growing season. So once again, thanks for joining us for this episode of the Weeds AR Wild 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.