Alternatives to Paraquat: Use of Tiafenacil as an Alternative to Paraquat to Control Row Middle and Preplant Weed Control

March 9, 2023

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This session was held as part of the vegetable crops track during the 2023 MI Ag Ideas to Grow With virtual conference. This virtual conference held February 27-March 10, 2023, is a two-week program encompassing many aspects of the agricultural industry and offering a full array of educational sessions for farmers and homeowners interested in food production and other agricultural endeavors. Sessions were recorded and can be found online at

Video Transcript

- This is AG Ideas to Grow With. It's a webinar series MSU put together just a couple of years ago. It's a two week long thing. It's pretty neat. And you got all sorts of things to choose from, from animal agriculture to fruit to field crops. There's a whole thing just about irrigation. In this session that you're in as part of a track on vegetables. So we're over halfway through the series for this week. We had Biological Management of Diseases and Insects on Monday, Salad Mixes on Tuesday, Sweet Corn on Wednesday. And both of those were at like a sort of an introductory level. Today we have a higher level talk for more experienced growers about a herbicide product that can work like Paraquat but can potentially be safer around people. And Dr. Sushila Chaudhari from MSU is going to be leading that talk. She's our weed scientist and she's been doing some data collection on this alternative to Paraquat. And then tomorrow we have another 101 level talk on root crops, just focusing on beets, carrots and radishes which is gonna be great. And Ben Worling, my other colleague, is gonna be leading up that talk. Our webinar series has been sponsored by AgriStrategies LLC, and I've been showing this every day this week, not actually knowing what this was. So I wanted to see and I went to their website and I'll just show you real quick. AgriStrategies is a consulting firm that can help you as a producer make more efficient decisions about cash flow, profitability and financial management. So it's kind of like a, maybe a CPA, I don't know if he's got a CPA certification or not. But someone can give advice on choice investments for your operation. And welcome, Sushi. Thank you for joining us today. Okay, Sushi ready to go? - Yep. Thank you Ben. Thank you for the nice introduction and good morning everybody. Thank you for joining us for this webinar series and I am Sushila Chaudhari, I am a weed specialist here at Michigan State University and today I will give you an update about the trials that I'm doing in peppers as well as in tomato and cucumber for looking at a alternative of Paraquat in these crops. So it'll be mostly to update related to those trials. So please feel free to ask if you have any questions. So as you all are familiar that the mostly people use Gramoxone or Paraquat for managing the weeds. Those are as the pre-plant, before planting in case of the stale seedbed situation or you know, in case of when the crop is not emerged and it's planted so immediately before emergence of the crop. And also the Gramoxone has been used in row-middles for managing the weeds. And mainly in this situation the shielded spray are recommended because if any droplet of Paraquat is going to go on the plant, it can cause the injury to the plant. However, in recent years, you know, due to its more toxic effect of Gramoxone on people's safety, growers have started using it less. And also for Gramoxone using, you need to do a some special type of drainings also. So because of these reasons, growers are kind of not that much of favor Gramoxone unless it is very necessary. So we are looking an alternative that can be used for manage as a Gramoxone. So there has been a lot of work going on for using the rely or you can say the glufosinate that can be used. And in case of the pre-emergence or in case of the role models, this work has been done since 4, 5 years now. So a lot of projects are going on through IR-4 related to this herbicide. So this glufosinate is Group 10 herbicide and there is another herbicide that we are interested now is Tiafenacil. This product is a PPO herbicide. It's belonged to group 14 and it is a non-selective herbicide. It controls broadleaf as well as grasses. It has higher activity in broadleafs as compared to the grasses. And at this point it is only registered to use in pre-plant or pre-emergence burndown in corn, soybean, wheat and cotton. It is more safer as compared to the Paraquat and it also does not have any dietary restrictions or any risk to the human health. So that is the main reasons that we are also interested to see how this product is going to do in our vegetable production system. In some of the countries like Korea, they are using this product as a alternative of Paraquat. So therefore we are, in 2021, I started doing some work related to this herbicide in cucumber, tomato as well as in pepper. So I will show you the two years of the work that I did in these crops in 2021 and 2022 of summer that I will share with you guys. Yeah, so in total we have done six trials in both of those years and those trials are separated based on the application timing as well as based on the production system that we have used and the crops that we have used. So now I'm not going to talk about all of them, but few of those trials I'm going to talk in this presentation. So the first trial that we did in 2021, it was in pickling cucumber. It was a bare ground production system and we use this Tiafenacil to control the row-middle weeds. So just want to go through the plan, how we lay out the trial. So when I'm saying the row-middle then these treatments were only applied in those 2.7 feet spray band that you see in this picture. This is the place where we have applied the Tiafenacil different treatments for controlling the weeds. And in this picture you can see how much weed pressure we have here in our field and the weeds that we have is redroot pigweed, lambsquarters and ragweed. Those are the mainly three species that we have in this study. And then we have these three rows of cucumber. So in this trial what we did, we applied the herbicide 30 days after the cucumber were planted and the application timing was selected based on the weed growth stage because at that time most of the weeds those were there, they were close to eight to 10 centimeter tall or we can say four to five inches tall. That is the recommended, you know, the stage for getting the maximum activity of Tiafenacil or any post-emergent herbicide can give us maximum amount of control if we are going to apply the herbicide at this stage. And these are the number of the treatments that we have. We have non-treated Gramoxone for comparison one lb ai/ac, Aim, that is 0.031 lb ai/ac. And then we have these four different rates of Tiafenacil from lower to highest rate. And then we have the tank mix of Tiafenacil and Aim, the lowest rate of Tiafenacil and then the Aim. So in this trial after application of Tiafenacil we evaluated the crop injury as well as the percent control. So in terms of the crop injury, the Tiafenacil crop injury is same as you see from Paraquat. You know those small dots that you see like wherever the spray drift is going to touch the plant, you'll see these small speckles, kind of the injury. It's something similar that you see with Paraquat. And we didn't see that much of injury. It was kind of like 10% or 15%. That was the injury level that we see that we saw in this trial. So now I want to show you the weight control that we got from this trial at the time of harvesting. So these are the pictures from the non-treated plot and I would like to say that these weeds that you see here, they were mowed because otherwise they were around, you know, close to one foot to one and a half foot tall. But we mowed so that we can do the harvesting of these cucumbers. In Gramoxone plots looks very clean, Aim, you'll see these green stuff, it's mostly grasses because Aim cannot control the grasses. It's mainly for the broadleafs. And then these are the plots where we have applied Tiafenacil. So in general when we have increased the rate, regardless of what rate we have seen, we have received good control of all the weed species and the Tiafenacil highest rate plot has a little bit of low growth of cucumber and that you will see later on also in my yield data as well. So this is the, I know I apologize for a lot of numbers, but just only one thing I want to tell you here is that in terms of the yield, the lowest yield was observed when we have used the highest rate of Tiafenacil. So that is telling that this 0.89 is a little higher rate for pickling cucumber to use in the row-middle. So in general, from this trial we find out that Tiafenacil provide a good control of common lambsquarters, common ragweed, redroot pigweed as well as grasses as similar to Gramoxone and Tiafenacil has a potential to use in pickling cucumber for row-middle controls. Now I'll talk about another trial where we have used the Tiafenacil in banana and cherry peppers for controlling the row-middle weeds. So similarly in this trial also we have treated these 2.7 feet wide bands. Those are on the both side of these peppers row. So one row of the pepper is banana pepper and the other row of the pepper is cherry pepper. That's what we have in this trial. And most of the weeds that we have is smart weed or you can say the Ladysthumb that you see here. Maximum amount is that one. And then we have common purslane and some pigweed species as well. Similarly, in this trial also we treated the plants, applied the treatments at when plants were two to five leaf stage and that stage achieved when the 21 days after the pepper transplanting. And we have the similar set of the treatments that we used in our pickling cucumber. So one lb/ ai/ac of Gramoxone that is equal to 2.7 pt/ac. Aim is 2 oz/ac and the Tiafenacil rates varies from 14 gm/ac to 56 gm/ac. And then the lowest rate of Tiafenacil 14 gm/ac and then 2 oz/ac of Aim. So in this trial, one thing that we've noticed that in terms of the weed species, Tiafenacil has provided more than 80% of the control regardless of rate and what weed species we are looking, this is common purslane, common lambsquarters, Ladysthumb and ragweed. And this control was 14 days after application. However, you know as the time is going and by 35 days after application the control reduced drastically because the new seedlings are started to grow in these plots. So this is telling me that if we have a crop that for a longer season we need to make at least two application of post emergence herbicide for managing those row-middle weeds. In terms of the crop injury, we have a little bit of higher crop injury in the pepper as compared to the cucumber and the injury is reducing as the time is going because plant is getting recovered from the drift injury that we have observed from Tiafenacil or even Gramoxone or Aim. So the level of injury is similar from Tiafenacil as from the Gramoxone. We did not see any reduction in number of the plant count that we made at seven days after application of the treatment. Just want to show you the visual representation of the plots, how they were looking. So this is the non-treated, you can see we have a pretty thick presence of the weeds in the row-middles. This is the Gramoxone, then we have Aim and these are the increasing rate of Tiafenacil in these pictures. And this is 14 days after application. And in terms of the yield data also we did not see any negative impact of Tiafenacil from any of the rate to yield of banana or cherry pepper. So overall from this trial also we observed that Tiafenacil has a good activity to control common purslane, Ladysthumb, common lambsquarters, redroot pigweed and control is similar as Gramoxone or Aim however, if you know in pepper, since the crop is a longer season crop, so we need to make at least two application to managing those weeds for controlling the second flush of these weeds. Now I'll talk about the third trial that we did in year 2022. Now we were also interested to know that can we use this product in case of the stale seedbed situation where we are preparing the bed and then letting the weed seeds to grow and then controlling them like you know similarly as we use our Gramoxone. So in this trial at this time we have applied the herbicide or the treatments in these three rows of cucumber at different timing. So these timings were pre-plant that like we prepared the field five days before the planting and then we applied the three rates of Tiafenacil, the 0.22 and then from 0.45 and 0.67. So those are the pre-plant application timing. And then we planted the crops and within two days of planting the crops we made the same herbicide application and that we calling as pre-emergence application. And in also we have the treatment, we have applied the herbicide pre-plant and then the second application was made as pre-emergence. So from this trial in terms of the crop injury, we did not see any injury from any of the herbicide treatment except from the high rate of Tiafenacil that was applied at pre-emergence. And the injury that we reported was a thin standup that was germinating of cucumber. And then also we have noted a good amount of the weed control when the Tiafenacil was applied as pre-emergence. That was two days after planting the crop as well as when we applied it at two timing pre-plant and pre-emergence. It has a approximate 60 to 70% control of the various weed species. And this time the weed species we have in the field is red root pigweed, wild mustard and common lambsquarters. I'm going to show you some of the screenshots from this trial. These are taken two weeks earlier than the harvesting. So you can see how our non-treated have a lot, mainly you see the wild carrot and maybe some pigweeds also here and there. And then this is the Gramoxone treatment. This is the low rate of Tiafenacil and then these are the increasing rate of Tiafenacil. And these treatments were applied at pre-plant, those were like five days before planting our cucumber. So we can see that we see a rate response when we are using Tiafenacil. At high rate we have high weed control and mostly because we have the good weed control, that's why our plant is also cucumber plant is also growing well as compared to in these four plots where weeds are competing heavily with the crop. These are the plots where we have Tiafenacil applied as pre, this was two days after planting the cucumber and we have really good weed control and plants are doing great. These are the treatments where we have applied Tiafenacil pre followed by pre-plant, followed by pre. And similarly here also we have a good control. So this Tiafenacil does not have any pre-emergence activity for controlling the weed. But the reason we are having or seen these good control in the pre-application timing because you know at the time when we made this pre-application, it was kind of seven to eight days since we prepared the field. So my hypothesis or you know, the reason behind this is that there might be those weed seeds started germinating and then when we applied the Tiafenacil, it killed those really small seedlings when they were like a really small stage. So that is the reason we have this good control from this Tiafenacil treatments. So in these two graphs I have the first graph on the top left is showing the cucumber yield and the bottom right one is showing the cucumber plant biomass. And on Y-axis I have these different rates. So similar to you know, the weed control because we have less weed control in our non-treated Gramoxone treated plots as well as in our pre-plant application of Tiafenacil plots we have lower yield as well as the lower plant biomass. Rest of the plots are having a really good yield because of the good weed control in those plants. So the trial from this, the results or summary from this trial or we find out that pre-plant application provided less weed control as compared to the pre-emergence application and Tiafenacil again has a potential to be used in pickling cucumber for pre-plant or pre-emergence application in similar way as we use the Gramoxone. Now just going to discuss the results of the last trial that we did in bell pepper and tomato in plasticculture system. So this trial we have conducted in East Lansing, Michigan and we have used one row, we have used the plasticculture system in this trial. So on the plasticculture we have one row of bell pepper and another row is the tomato. Those are Primo Red tomato ready. And in this trial we have applied Tiafenacil treatment at three different timing. So the timing are we applied pre-transplant and those were before laying out of the plastic. So one day before laying the plastic. And we have picked all these three different rates, those were applied at pre-transplant and then the same, these three rates were applied at post-transplant. Those rates were 0.022 lb ai/ac to 0.67 lb ai/ac. And those pre-transplant treatments were applied when we laid out the plastic and over the plastic those treatments were applied. And then we have the pre-plant treatment that we applied over the plastic and also we applied the irrigation 24 hours after that application so that if there is any residue of Tiafenacil on the plastic, that will wash away. Just to see that, do we need an irrigation after making the Tiafenacil application in those plastic to see if there is a need of irrigation or not? So from this trial, in terms of the crop injury, we did not take any weed control data. We just took only the crop injury data. So we have some amount of injury when we have used the like higher rate of this Tiafenacil applied over the plastic, pre-transplant over the plastic. And the one thing is that this is because the injury is higher because some plants got dead but the main reason for plant death was not clear like it is because of the transplanting shock or it's because of the herbicide. So you know, because that happened only in the bell pepper. In tomato, we did not see any plant reduction or like, you know, very low level of the injuries that we have seen here. And these injury ratings were taken 20 days after planting. So it was kind of both a combination of the herbicide as well as for the transplanting shocks as well. But after this rating, the plants were doing really great and we did not see any injury symptoms from any of the herbicide treatment. So similar to the previous graphs, in this graph also we have on Y-axis the pepper yield and on X-axis we have different Tiafenacil rate. Those were applied pre-transplant over the plastic. Over the plastic with irrigation and under the plastic. And from in terms of the yield, we did not see any significant difference in yield. Similarly with tomato also the yield were showing similar to non-treated there was no negative impact of either the application timing or application rate or tomato yield. So overall from this trial we find out or concluded that the Tiafenacil application under or over the plastic mulch regardless of with or without irrigation application for removing the herbicide residue does not impact tomato or bell pepper growth or yield as well. And the Tiafenacil rate has a potential to be used in both tomato as well as in bell pepper plasticculture system. So what we did from both of these year's trials that we submitted these data to IR-4 in the 2022 Food Use Workshop so that we can take these projects upper and then can set up a maximum residue limit for Tiafenacil in various vegetable crops and that will help us to potentially registration of this product to use in our vegetable production system for row-middle as well as in pre-plant burndown. So this project was selected in IR-4 Food Use Workshop for doing the residue studies in 2023 year, in growing season of 2023. So from there we'll see how the data will turn out and hopefully in near future we'll have the Tiafenacil to use in our vegetable production system for managing the row-middle as well as the pre-plant weed control. With that I would like to acknowledge all the funding sources for this work as well as all my helper or all my lab members who did a tremendous amount of the work for doing all these trials and I'm more than happy to have any questions. The fun part begins now. - You've had questions come in the whole time but you were on a roll so let's go back to the top. - Yeah. - First question you got was right at the beginning and it was about what differences do you see in Reviton which is Tiafenacil and Sharpen, which is Saflufenacil, they're both Group 14. Would they behave the same? Is there a, I don't know. - And if I need to describe Tiafenacil, it is very close to the Sharpen in terms of the activity as well as in terms of the chemical group from where they both belong. - Do you feel like one over the other is easier to get new label uses for? - Yeah, that's what we are hoping that with Tiafenacil. Okay, so let me take one, let me tell one more thing that in terms of the activity or in terms of their efficacy in the weeds, they both are similar. I am not familiar about the non-target effect on non-target organism, like how toxic is Tiafenacil or how toxic is, like which one is more toxic. So maybe that could be the difference that we are more going with the Tiafenacil, you know, it may be easier to register Tiafenacil as compared to the Saflufenacil. - Yeah. One of the other questions you got was from someone to ask if you were monitoring the impact on soil living organisms like microbes and beneficial insects. And my response to that was to link to the safety data sheet for Reviton. The actual chemical isn't new, so there's a lot of data on it, it's just it's use in vegetables is what Sushi is sort of figuring out right now. - Yeah. - So that safety data sheet has what they call ecological toxicity information and what they do is they set up trials basically to see what the effects are on things like, the species I see on it are rainbow trout, Daphnia magna, which is a really tiny microscopic water bug, algae, an aquatic plant named Lemna gibba, bobwhite quails, mallard ducks. And I think that's all I see on this one, but it's limited how much can be tested. But this product has been around a while and it's passed various tests and doesn't sound like what you were asked to do for this project, was it to look at that kind of thing? - No, I didn't look for that kind of things like, yeah. - Okay. Another question you had was from William. He asked, "Do you think there's a short period of residual effect on germinating weeds?" - I confirmed with the other people also and then everybody responded to me is like, "No, Tiafenacil does not have any pre-emergence or residual activity." So, and I just have only two years of experience with working this product, so maybe something we'll see this year, but based on my conversation or it says like, no, it is not. But I was very surprised to see the amount of the control that we have observed in our pickling cucumber trial with the pre-emergence application. And I'm just thinking maybe it is because at that time the weeds were already germinating and they were really small. - Oh. - Yeah. - I was looking at our weed guide to see, since Nick asked about the difference between Reviton and Sharpen, I wanted to see if Sharpen was labeled on vegetables and it is labeled for peas. - Peas, yeah. On some. - And I believe it's, oh, I gotta double check. I think it's labeled for pre-emergent use. So let's see here. Surface burndown pre-plant incorporated in Michigan, Illinois, Iowa and Minnesota only. So I guess in some states you can use a related product as a pre-emergent herbicide. So maybe, I don't know, it sounds like the people you talked to said no, it doesn't work that way. - Yeah, yeah. For Tiafenacil they have told me like, "No, it does not have a pre-emergence activity," so I'm just using their word. - Alrighty. - Yeah. - That might open a whole can of worms for them. - Yeah. - You got a couple of questions from Kristen Obeed, I believe Kristen's in Canada. First question from her was, "How soon after application did you transplant the tomatoes and the peppers?" - So we transplanted at least two days after application because over the plastic when we made the application. Then after 24 hours of that application we did the irrigation and then next in the following day we planted them. So it was two days of gap between the application and transplanting. - Okay. The other question that Kristen asked, it was more of a comment or a suggestion she said, "It would be nice to do some joint work with IR-4 and PMC in Canada, they do minor use trials in berries." - Mm-hmm. - So Kristen Obeed might be a person to work with in the future on some of this stuff. - Yeah, so this project has been selected in IR-4. So, and I don't know in which state they are going to do more trials, but I know that in 2023 there will be some efficacy trial as well as some residue trials will be conducted related to this use. - Okay. Another question from William. He said he noticed that Tiafenacil is labeled for grapes. - Yes. - Do you have any information on its use in grapes? - Yeah, so it is labeled in grape for, you know, to using as a burndown in summer application. And also they are planning to, I'm not sure if that label is already there or, but they are also applying for control of suckers by using Tiafenacil. So yeah, but I'm not sure if that is already out or that is in the process. So controlling both the emerged weed during the season, like as we use the Rely, you know, and then also controlling the suckers. Those are the two main users. - Okay. - And I think the product is Gamma, that's the name of the product that is labeled for using in grapes. The trade name is I think Gamma, G-A-M-M-A. - Okay. Another question came in from Herm. He wonders, was there compound residues left in plant tissue? He notes that many people don't want to eat stuff that has chemical residues in it. Maybe you could speak on the target of the spray and how it breaks down. That might be a way to answer that. - Yeah, so the thing is like for Tiafenacil, since it's a new herbicide, so there is no residue trial has been done. So when I'm saying that IR-4 is going to do, or this year the residue trial, the residue trial is mainly for evaluating that how much compound is there on the plant after making the application. So there will be a residue limit set and after that we can use this product. At this point, there is no residue limit set. Did I give the answer in the right way or? - Yeah, that makes sense. So basically if there's no residue limit set, what that means is if a crop gets sprayed with it on accident, the government would consider that an adultered crop. - Yep. - 'Cause there's no information on what is the safe level that can be in it. So as a part of opening up labels to be used on different crops, these kinds of studies do have to answer those questions. And Sushi is on one side of it, looking at plant damage and efficacy on weeds are you also gonna be looking at the residue stuff or is that another person's product? - Yeah, another person that trial is going to go to another part of the state. - Okay. And this is all under the IR-4 umbrella? - Yeah, all under IR-4 because IR-4, you know, is the entity who helps for registration of this product. So for any product registration, IR-4 need the efficacy and crop safety data as well as the residue data. - So that's still coming? - Yeah, that's still coming, yes. - Okay. So this isn't labeled for any of these uses yet? What you're looking at is early efficacy data on its effects on the plants and the weeds around those plants? - Yes, yes. Yeah. It's just like we are trying to, and this is the first time I, like we have done this trial or maybe anybody has done this, uses to evaluate to see if we can use these, you know, in vegetables or how can we potentially use or kind of like, I'm trying to bring another tool in the grower's toolkit that they can have, you know, for managing the weeds. So yeah. - Great. Fantastic.