▶ Managing Waterhemp in Spring Alfalfa Seedings

05.080 → 31.100
Thanks. So I’m going to talk about some options for controlling waterhemp in the spring alfalfa seedings. Dan did a really good job of emphasizing why we’re concerned about waterhemp, so I’m not going to really go through these issues. I will say that, you know, 90 plus percent of the concern really comes from corn and soybean crops is where the concern is.

31.120 → 51.120
And so I work in forages. So in Wisconsin, that means alfalfa. So the question I really have is “What’s the impact of waterhemp in alfalfa?” You know, alfalfa is a little bit of a unique crop where we have a seeding year and we have an established year that you can more or less think of as two different crops.

51.140 → 01:14.220
And we really don’t have nearly as much data on how impactful waterhemp is in alfalfa. Well, we have, as a group, done quite a bit of work in established alfalfa. And, we have summarized some of our reports, and I believe Anastasia is going to put a link in the chat about that. But what we found is in established alfalfa,

01:14.240 → 01:42.160
We really were effective at controlling waterhemp do, in combination of both the just competitive nature of alfalfa, where it grows really quickly in addition to the, rapid cutting in the dairy system. We just don’t get that plant to develop a lot of biomass and produces very few to no seeds. It’s still present in the corn grown next to it, but because of that alfalfa, we can really effectively control that.

01:42.180 → 02:06.230
So I’m not going to talk about in established alfalfa. We have pretty good results that suggest that it’s a good management option by itself. As long as an alfalfa stand has enough plants. But the big question we don’t have a lot of data about is what about in a new seed in the spring? How competitive is alfalfa and what are some effective management approaches?

02:07.000 → 02:30.120
So I think here, if technology will work, we’re going to have a yeah, it’s working a poll. We’d like you. We’d like to know from you guys how do you control waterhemp in a spring seeded alfalfa planting. You can pick, I believe, from any of those options. You either don’t control it. You use some type of a pre plant incorporated herbicide.

02:30.120 → 02:58.050
You use glyphosate post and Roundup Ready alfalfa, an ALS herbicide. You know, what do you use? And so I think while that goes that, that survey goes on, hopefully you guys can give that answer and we’ll summarize that and understand better. I think I know what people are using, but it’d be good to know those, those results from people online.

02:58.070 → 03:24.140
Okay. I think we’re going to just continue on. So what options do exist for controlling waterhemp in new seedings? So I pulled this out of A3646 that Dan mentioned. This is our rating system and our herbicides that we use for waterhemp. And as you can see, we’ve got a wide range of herbicides that are give us anywhere from a seven to a ten.

03:24.160 → 03:50.210
We can apply those pre plant incorporated to alfalfa such as Eptam and Treflan at alfalfa emergence, up to the, I believe this is the, fifth trifoliate leaf. Butyrac, after emergence, we can apply and then a lot of others that have other restrictions towards the timing with alfalfa. But the challenge in this isn’t really, only the alfalfa timing

03:50.210 → 04:11.100
When we apply these, the challenge is also timing it correctly with the weed stage of development. And a lot of times these are our have different recommendations and these aren’t lined up. So here’s some of that information for these different products. And I’m just going to go through some of these together just to emphasize some of the differences.

04:11.100 → 04:40.080
So for our pre-emergent our herbicides that work only before, only on yet to emerge waterhemp or weeds. We’ve got four options. The preplanned incorporated ones, we really don’t have an issue with because we’re incorporating those. Warrant, the encapsulated acetochlor, works really well. But we need it needs to be activated by precipitation, as Dan alluded to.

04:40.080 → 05:02.150
And many of you probably saw we had issues with that this year, where we waited several weeks for that activated rainfall. Prowl was a good option, but Prowl is where we have this mix up with when you can apply it, on the alfalfa and when you need to apply it for the weeds. It has only pre-emergent activity, but you can’t apply it till after two.

05:02.150 → 05:34.150
Trifoliate leaves on alfalfa. So by that time, that first flush you’ve already missed. And so that’s one of the challenges. For various reasons, most people are relying on some type of post emergent approach. Historically, we’ve got a range of options from glyphosate to, Butyrac, and Pursuit or Raptor, or Bromoxynil and remember, Dan mentioned that cola can size four and a half inch size, tall weeds.

05:34.210 → 06:02.130
So that is the case for glyphosate that that’s the timing. But the big issue that we want to emphasize for some of these other products, it’s much smaller than that four inches. It’s three inches or sometimes even two inches or less. So make sure you nail that timing or control will be limited. Then the biggest issue that we need to think about, particularly with waterhemp, is what is your status?

06:02.150 → 06:32.220
What is the status of your populations? Are they resistant to these herbicides? We feel that both Pursuit and Raptor, that Group 2 herbicides, and glyphosate, we have widespread resistance from by waterhemp. And so likely these aren’t an option for management. I will note that several of these have, a higher degree of alfalfa injury potential, but, we can talk about that in the Q&A later.

06:32.240 → 06:53.100
So what I want to talk to you all about is an alfalfa checkoff grant that we got to look at using alfalfa as a weed management tool. And it has to do with some of these issues that we talked about, that Dan talked about in that one on farm example, but I’m just going to pull up.

06:53.110 → 07:23.060
We just started this project. So I’m just going to show you some of the data, related to alfalfa productivity. How we did this experiment: We did this in three locations. I’m just going to talk to you about Wisconsin. The spring, we established plots in the spring. And I’m going to talk about three of the different treatments we used. Warrant, which we applied when the alfalfa emerged. Butyrac at the two inch tall weeds, 2 to 3 inch tall weeds.

07:23.060 → 07:50.080
And we had another treatment where we added Prowl H2O at that time as well. And we’re going to show you those results. And we did a bunch of measurements. We’re not going to talk about the seed bank. We’re going to really focus on the control and the resulting yield from the first cut. So we planted in Lancaster, Wisconsin 4/22. We got some time when rainfall alfalfa moves right around the end of April.

07:50.080 → 08:21.100
We applied that warrant on April 30th. And as you can see here, no rain for two weeks. So what that means is we had no active herbicide and we had a flush of waterhemp, two weeks early, that emerged before we got activation of that herbicide. That’s poor control, much poorer than we would typically receive. Then I want to just emphasize we applied the Butyrac treatments in late May at the 2 to 3 leaf stage.

08:21.100 → 08:44.240
That was this was the height that we saw of the water. And so we nailed that timing. So that was really good. And you’ll see that in the results. The bad news is, is they had an extremely high weed seed bank of waterhemp in this field. So literally carpets of waterhemp by the time we made this application.

08:45.010 → 09:12.050
So worst case scenario here. So what did it look like? So we came back middle of June, 25 days after post application. One of the things looked like where we had no control. We had a sea of waterhemp. It had topped over the alfalfa and was outcompeting the alfalfa. When we applied Warrant, we did get some control. You can still see the rows of alfalfa if you look close.

09:12.050 → 09:38.160
But we missed that first flush. So some of those weeds had emerged by the time it started to work. In contrast, the Butyrac treatments were looking great. We had suppressed the waterhemp. It wasn’t killing all of it, but the alfalfa was on top and really actively growing. So what does that turn into cover? What we see is in the non treated areas which are the hash, the dots, dotted line.

09:38.180 → 10:04.200
We have essentially 50 to 60% cover that last month before we harvested that alfalfa. The Warrants, although we missed that first flush we still had some suppression of the watehemp, and that cover remained around 35%. But those Butyrac treatments really are showing their benefit. We’re reducing that waterhemp cover down to 10% or so by the time we harvested.

10:04.220 → 10:35.170
How did that relate to alfalfa? Well, you can see those Butyrac treatments really look good. And we’re getting a doubling of that alfalfa cover over that one month time frame from 40% to 80%. In contrast, that Warrant treatment went from 40% to 60%. So 15% increase and only a 5 to 10% increase in the non treated controls. Let’s show some pictures because that’s really worth a thousand words.

10:35.190 → 10:58.040
So here we see the treatments. Here’s our non treated control. You can clearly see a sea of waterhemp. Really tough to see that alfalfa. In contrast the two Butyrac treatments look great. Where the alfalfa is on top of the waterhemp, and the waterhemp was suppressed. The Warrant treatment, again, lots of waterhemp. But we can still see the rows of alfalfa

10:58.040 → 11:17.000
When we’re harvesting. Much better than you see the non treated control in the distance where the waterhemp has come up tall. So we just have first cut yields. So we’re going to take a look at those. First off, the overall yield range from a little over a ton to a ton and a half of dry matter per acre.

11:17.020 → 11:36.240
Although you see some of the bars look different, there was no difference in yield among the treatments. But when we look at the alfalfa yield, we saw that the Butyrac treatments had around a ton of alfalfa that was produced. When we had Warrant, we were around, a ton and a half or, three quarters of a ton.

11:36.240 → 12:01.230
So had a slight reduction, although not statistically different. And the non treated control, we had half as much alfalfa — a half ton. And you could see correspondingly with the yellow bars. That’s the biomass of waterhemp. And we can see when we’re applying the Butyrac we’re keeping that biomass of weeds to around 10% or so in that first cut.

12:02.000 → 12:32.140
Whereas with the Warrant it’s around 50-50. And in the non-treated, we have more waterhemp than we have alfalfa in that first biomass. So that’s some of the results from the first cuts. You may be wondering, man, we’re probably getting a big hit on alfalfa sand density from these treatments. Our initial results are showing no significant difference in losses in stand and alfalfa plant density from any of the treatments, although you can see a trend with lower plants.

12:32.140 → 13:06.200
My guess is, with this frequent harvest, the alfalfa will, the stands will look great. So what can we conclude from this data? Well, the first conclusion that we can make from the first cut is that Butyrac, at two quarts per acre, worked well at effectively controlling waterhemp. Warrant gave partial control. I really feel that that’s due that lack of activating precip right after we sprayed and in combination we had that waterhemp for some reason emerge a week to two weeks earlier.

13:06.200 → 13:39.090
So that one two punch really gave us poor control that we haven’t seen before with Warrant. So the big question is, how does this these results, how are they going to impact nutritive value of the forage and milk production? Well, those non treated controls and Warrants were going to likely get an impact on that typically around 20% or more biomass of weeds in your in your yield is going to reduce your milk production.

13:39.110 → 13:59.120
But those Butyrac treatments, we’re probably not going to see a difference, particularly if we harvest those in a timely fashion because it’s it was around 10% and below that 20% level. So that’s the good news. We do have some future questions we want to answer with this research. We’re interested in how it’s going to control the future harvest.

13:59.130 → 14:26.050
And I’ll show you some pictures in a second. And obviously we added Prowl in that one. We’re curious if there’s any value in adding Prowl, or is that not giving us any improvement in long term control? Okay, let’s look at some pictures. So we went in two weeks after harvest and took some pictures on your right. This is what the non treated control look like in June. See a month later it looks great.

14:26.050 → 14:59.070
We have alfalfa way up above that waterhemp and mostly alfalfa. If you look in deep you’ll see lots of little waterhemp plants that are growing. Those are likely ones that were too low to be harvested. Those larger ones look to have been, senesced and controlled. The Warrant, similarly looks really good compared to the initial treatments, like the untreated control we are seeing significant seedlings that are present in there, at a slightly lower density, but similar to the control.

14:59.070 → 15:27.120
But alfalfa stands look really good. How about those Butyrac treatments? They look good in the middle of June and they’re continuing to look good in July. Not seeing a lot of seedlings that have emerged, I think we got really good control. I’m not seeing some of those later flushes. We do see an occasional waterhemp plant here or there, but much lower density and we’re seeing in the, in the Warrant and the non-treated control.

15:27.150 → 15:56.090
And same story with the Butyrac and Prowl. Again, they look very similar to, to the other ones as well. So the big question is, is what’s going to happen when we harvest this at the end of these months? And so here’s my, crystal ball of what I think’s going to happen. I believe that, and I’m basing this on some data where I’ve summarized seven trials where we’ve collected weed biomass in the first and second cutting.

15:56.110 → 16:24.170
This is averaged across these seven trials where I looked at the percent weed biomass in plots that were never treated with a herbicide and compared those to treatments that had the best treatment that was applied during that seedling phase. And what we saw in the second cut is if we didn’t do any management in that second cut, we had anywhere from 10 to 27% weed biomass in that second cut.

16:24.190 → 16:55.190
That’s in comparison to 50 to 80% in the first cut. So we still have an impact, but it’s much less than that. We see, whereas if we have really good weed control, it’s really a non-issue because, while we will get some weeds show up later, it’s in that 0 to 5% range. And the key point I’m trying to make here, what I think’s going to happen, is most of these are below this 20% threshold of percent weeds in the biomass.

16:55.200 → 17:16.010
If we can keep that those weeds below 20%, we’re likely to not see a difference. So as you can see in the non treated ones, we may in some cases see a reduction. In some cases we won’t, but we’re in pretty good shape with the other ones where we do we likely will not see a difference in nutritive value.

17:16.030 → 17:38.060
So to kind of finish up alternatives to glyphosate, ALS herbicides are effective at controlling waterhemp in new seeded alfalfa. Timing is critical for these post applications. If you’re going to use Bromoxynil or Butyrac, we can talk about in the Q&A, the differences between the two. So small weeds is really what’s needed.

17:38.080 → 17:58.110
If you’re going to use Warrant, you need to have that activity and rainfall, and we don’t get it, our control fails. I think some of these pre plant incorporated herbicides work can work well in moderate to low density situations. We did have some trials with Eptam and Treflan just next to this trial. And we got around 30 days of control of waterhemp.

17:58.130 → 18:21.150
But that was weed populations. That seed bank was so high that those populations reared back and were really competitive. So may work in moderate to low density. In these high densities, it really wasn’t giving us effective control. The last thing I’ll point out is that the injury potential is higher in many of these products. And so we really need to also think about that, particularly Butyrac.

18:21.150 → 18:45.010
And Bromoxynil. These are older chemistries. There’s a reason why we got away from them. It’s because of the higher injury potential. And the in some cases reduce efficacy if we miss some of the timings. What are we going to be doing with this one? We’re going to be turning our gears and focusing on this waterhemp seed bank and see if alfalfa is going to reduce that seed bank.

18:45.070 → 19:10.020
And the importance of this first year, weed management. Waterhemp seeds last 4 to 6 years in the field. If we can keep those fields from producing any viable seeds, other studies have shown, you know, 95 to 96% reductions in seed banks. So we’re really optimistic we’re going to see a large scale reduction. We’re going to be tracking this.

19:10.020 → 19:37.000
We expect very low seed production in alfalfa in the seeding year and subsequent years, even if we don’t manage it. So we’re really interested to track some of that information. My colleague who’s the head P.I. on this, Sarah, Doctor Sarah Kezar are also looking at using low rates of Pursuit when that waterhemp is flowering to prevent viable pollen formation and further reduce seed production.

19:37.000 → 19:59.120
So more news on that probably next this winter or next spring when we put out those treatments. So with that, I’d like to again thank the alfalfa checkoff for funding this. This is a picture of Doctor Sarah Kezar, who was the lead P.I. on this project and others that are helping us. And if we have time, I would love to answer questions or hear comments.

19:59.120 → 20:23.120
And I believe we’re going to try and do this survey again and see now that you’ve seen some of these initial results, are you going to how do you plan to control water in spring and spring seeded alfalfa. We have this exact same question. Kind of interested in seeing if you’re going to change your answer at all. So feel free to answer that question.

20:23.140 → 47:00.110
And thank you for your time, and amazingly, Dan and I did not go over. So we’ve got a good 15 minutes for questions.