LISTEN: “New” Herbicides Could Soon Be An Option for Blackberry Growers

[00:00] Intro/Outro
Welcome to the Arkansas Food, Farms & Forests Podcast. The podcast bringing you the latest on food, fiber and forestry research from the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas System Division of Agriculture.

[00:17] Jenifer
Welcome to Food, Farms & Forests. I’m your host, Jenifer Fouch. Today we are talking about testing “new” herbicides in blackberry production that could give growers more options for weed management. Joining us to explore this topic, is Dr. Matt Bertucci, an assistant professor in the horticulture department. Matt, thanks for being here with us.

[00:37] Matt
Yeah, thanks for having me.

[00:39] Jenifer
So, can you give us a summary of this report and the key findings?

[00:43] Matt
Sure. So, in this study, we were looking at testing different herbicides to control weeds and blackberry production. And we were kind of assessing while we put quotes on “new,’” we were looking at using herbicides that have been long used in row crop systems like rice, corn, soybeans, but that might have utility in blackberry systems. So, the two products that we were looking at were 2,4-D choline and glufosinate. And just assessing whether they can be safe for use in blackberries and whether it can be effective for controlling the weeds.

[01:17] Jenifer
So, they’re not new herbicides, but they’re just new in blackberry.

[01:21] Matt
Yeah. In fact, 2,4-D is one of the first synthetic herbicides that were used in agricultural production. I think there was a 1940 paper about using that in sugar cane. And then in some other row crops. It tends to be really good at controlling broadleaf weeds, as opposed to grasses. And, it has some utility in this system because we needed something that can kill broad leaves in our blackberry plantings.

[01:48] Jenifer
How did this idea first come about? Of using something that is not new, but that has been used in other crops in blackberry?

[01:55] Matt
Sure. This is a common thing that is done, that we … The industry pursues registration for pesticides, and insecticides, and herbicides in major row crop systems. They’re the largest acreage. Therefore, they’re the biggest market. But the USDA is aware of the importance, the market importance, of specialty crops that are smaller acreage but still have large economic value.

And so, what we have is a thing called the USDA IR-4 program. And the IR-4 program works with chemical companies and says rather than going through all the trouble of registering, registering a chemistry, we will, facilitate that registration, and the USDA will support that activity financially and, recruit scientists.

So, the IR-4 program exists to support specialty crops and pursue registrations of different agrochemicals, things that can help us grow these crops better where the market doesn’t justify that, as far as a chemical company goes.

They can sell a lot more chemicals if they get a registration for something like soybeans, that’s on millions and millions of acres, as opposed to something like blackberries, that’s thousands and thousands of acres.

And in this case, the USDA facilitates the registration not by making it any less safe for use, but by lifting some of the expenses and some of the logistical barriers. And instead, working directly with scientists who are also advocating for that, because we want to make sure that our specialty crop growers are supported as well.
[03:37] Jenifer
I also read in the report that there are not a lot of options when it comes to herbicide products for weed control in blackberry. Why are there so few?

[03:49] Matt
That is true. There are limited options for herbicides for use in blackberries for two reasons. One is the industry, you know, can’t make as much money by selling those products. So there tends to be less discovery and investigation in pursuing materials that are suited for these types of crops. But also the crop is very sensitive.

And so, if you can think about some of the, you know, the most widely used herbicide, is glufosinate Roundup, that would be one of the trade names, is used because we have Roundup ready or Roundup-tolerant soybeans, and corn, and cotton. And so, we don’t have this genetically modified traits. We don’t have glufosinate tolerant, or, you know, other materials like that in our blackberries.

And so, the fact that we don’t utilize genetically modified organisms in these specialty crop systems, and then the fact that the blackberries are just sensitive to a lot of the chemicals that are commonly used.

[04:46] Jenifer
So, in this report, you talked about specifically 2,4-D choline and glufosinate. What were the findings? They were conducted separately, different conditions. Can you talk about the how and what were the findings on those two different ones?

[05:04] Matt
Sure. So, I’ll start with 2,4-D choline. As I mentioned, 2,4-D is one of the, you know, most historically utilized synthetic herbicides. It actually mimics a plant hormone, oxen. And so, it just disregulates the expression of these hormones or the, you know, the plant growth pathway.

So, the plants, there’s a very characteristic symptom where the plants start to curl up, they start growing in a peculiar way, and that will kill the weeds that you’re trying to kill. And, of course, we don’t want our blackberries to get all curled up and twisty and kill those blackberries. So, with the 2,4-D trial, we were assessing the performance of 2,4-D choline in established blackberries. And that’s important because this is a perennial crop; something that’s been in the ground for 3 to 4 years is a lot more tolerant of exposure to certain herbicides than something that might have been newly planted.

So, we were working with established blackberries, and what we did was we came out with an application of this material before the plant broke dormancy. And that’s a lot of times the plant’s safe from exposure because it’s not actively growing. And then we had another application, once the plant has broken buds and it is now actively growing. And then we had one after harvest as well. And we did that over two years and monitored, you know, against a plot that did not receive any of the 2,4-D choline.

And, you know, the good news for our growers, the good news for the industry stakeholders is that, you know, we saw comparable yields, where we saw injury or, or symptoms of that 2,4-D choline product, they were ephemeral, which is to say, they only showed up in a short period of time. And it was only a very small portion of the foliage.

So, we were testing was crop safety. Previous work and lab work is done for residue testing, to make sure that it’s safe and it doesn’t cause any harm for consumption or things of that nature. But we were able to assess and say, you know, it has a green light with regard to crop safety.

So, the glufosinate worked out very well. That was very different because glufosinate, we were testing on newly planted blackberries. So, then we took these really sensitive plants, you know, small little plugs that were between 6 and 8in tall, that we planted into the ground. And then we sprayed those herbicides. And I will say if we had sprayed that herbicide directly on those plants, that would have caused some big problems. Glufosinate is not selective. It will cause injury to the blackberries if it’s applied improperly.

So, what we did in this study was simulated shielding the sprayers. So, we used what a grower can use, and it’s sold in an orchard supply store, wax cartons, just milk cartons that we put around those small plants. And then we were able to apply that herbicide around the plant to make sure weeds aren’t growing, you know, in that immediate space around the plant and then observe. Was the plant injured? And unfortunately, that barrier worked very well. After a short period, you remove those wax cartons and we reapplied again 30 days later as the plant had grown up.

And blackberries grow really fast in Arkansas. So, we were already trellising them up and we were doing what was called a directed spray. So, we sprayed it to the soil, you know, targeting weeds that are going to be beneath that vertical canopy of a blackberry. And what we did see, we saw symptoms, glufosinate did cause a little bit of leaf burning.

But it’s a contact herbicide, which means it touches the plant and it causes symptoms where the herbicide touched, but it doesn’t move throughout the plant. So in the case of a five foot tall, you know, 5.5ft tall blackberry plant, symptoms in the bottom six inches really aren’t very concerning. And, we did this over two years too. And in the first year, we were able to see a little bit of symptoms on the lower canopy. In the second year. We did see some symptoms in the lower canopy again.

But what was interesting is blackberries like to make new primocanes. So ,they keep pushing out new little runners and shoots in the area between plants. And so those would get smoked and in one sense you’d think, oh, you know, that’s not good. Are you harming the blackberry? But in fact, that’s actually giving us a benefit because growers have to go out there and prune those back anyway.

And because this is a contact herbicide and it’s only killing where they’re emerging as opposed to killing the whole plant, it was actually serving an additional purpose. So that was a, you know, a side observation. As far as the weed control, this is true for both of the studies.

The reason we were excited about glyphosate and excited at about 2,4-D choline is current registered products for post emergence application in blackberries only control grassy weeds and two for the choline and glufosinate will give us some broader activity and let us go after a different set of species that really can cause fits for our growers. So, we’re excited about the opportunity to kind of broaden the spectrum of control with these products.

[10:28] Jenifer
Yeah. So, let’s talk a little bit about that. So, where do you hope these results will take the industry? What do you hope that will be accomplished with what you have found, what it could mean for scientists and for growers?

[10:41] Matt
So as a scientist, we want to say that not only was it injured or not injured, like I just said in this interview, we can say to what degree and where they are statistically different and all those things. So that goes into a report that’s not terribly exciting for the public to look at, but it is of great value to the industry.

And so, this was a partnership with the USDA IR-4 program. And we give our data, you know, multiple researchers worked on this project. People in North Carolina, people in Oregon, myself here in Arkansas that way were testing multiple soil types, multiple species, multiple rainfall patterns and ensuring if this herbicide is registered for use in blackberries, is it going to cause problems for people on the West Coast? Is it going to cause problems for people in the southeast?

So, we have a national assessment, not just one individual researcher. And so all of that is compiled. And then the chemical company, the industry partner, will look at the data and say, okay, given the support and, you know, the reduced, you know, paperwork and frustrations that registering a chemical product takes with the support of the IR-4, we’re going to support registration of this product for blackberry growers, you know, across the country for raspberry growers because there was a raspberry trial as well, but for these growers across the country.

So, we’ve got support of the industry partners. We have compiled data and now we’re hoping to, you know, ensure that that registration is actually publicly released because at this point, it’s, you know, in the pipeline.

[12:17] Jenifer
Okay. So we’re on the way there.

[12:19] Matt
On the way. We are towards the tail end of it, I would say, right. Because we’ve demonstrated the safety. I’ve shown growers., right, look, we have all the reason to believe that this is safe. That doesn’t mean you can go do it yet. Right? We need to legally be protected because, the USDA and the EPA are going to ensure, okay, if you use this, you have to use it at this rate, and you can’t use it after this date or, you know, near this body of water, because there’s environmental concerns as well. But that’s a lot of the support that the IR-4 program provides because it’s a lot of difficult… it costs a lot of money, and it takes a lot of resources to do these environmental assessments. The good news is we know the environmental behavior of these products. It’s well known how it behaves in the environment. So we don’t need to generate new data for that. But we did need to generate new data about crop safety. And so we’ve done all that. It’s all put together. And now it’s just a matter of, you know, the government working at its pace, of of getting that federal registration of that product so that all growers can use the material.

[13:23] Jenifer
Did you encounter any challenges for either of these herbicides or the entirety of conducting this trial?

[13:30] Matt
Sure. So, you know, what would be a challenge is if anyone knew I was spraying 2,4-D near grapes, they their jaw would drop. And now, you know, some people might not be familiar with that, but grapes are extremely, extremely sensitive to 2,4-D. Tomatoes, as well. A lot of times, these specialty crop plants are more sensitive than our most sensitive analytical devices. So, we can test down to, you know, parts per billion, but the plant can be even more sensitive than that. They’re very, very symptomatic, if they’re nearby any applications of this material.

So, I made this 2,4-D application on the Fruit Research Station in Clarksville, where there are historical vineyards and there are plenty of high value blackberry plants all around the, you know, application site. So, I had some anxiety thinking, you know, Dr. Lee is not going to be happy with me, Dr. Worthington is not going to be happy with me if their grapes get all curly because somebody load loaded up 2,4-D in a spray tank and sprayed 2,4-D on their farm. But the good news is this is actually a formulation of 2,4-D that is less volatile, that is less likely to move off target.

2,4-D choline, I made sure to say that a couple of times is different than 2,4-D amine or 2,4-D ester. Those were, you know, it’s the same herbicide in terms of the same material that’s killing the weeds. But it’s formulated in a different way. And this formulation stabilizes a little bit more so that it stays where you put it, and it just goes to the weeds, as opposed to maybe hitting the ground and then evaporating, vaporizing and moving to, you know, nearby, crops. And so we were very pleased that we didn’t have any complaints.

Like I said, as a weed scientist, I had some anxiety. I thought, I don’t want to take 2,4-D near a vineyard. But sure enough, this 2,4-D choline product, not only was it safe for blackberries, but we didn’t see any of the common, off-target consequences that you may see with some of the other 2,4-D products. So that was exciting and nerve racking.

[15:43] Jenifer
And you’ve mentioned a few here and there. Were there any anything that was surprising to you that you were not expecting?

[15:49] Matt
Sure. So, a pleasant surprise, probably, like I said, was the fact that, you know, I was in the clear with those grapes. I was, I was surprised. So we, I mentioned previously that glufosinate is a contact herbicide. I felt pretty confident if we sprayed that at the base of a, you know, five-foot-tall blackberry, you’re probably just going to see a couple, you know, injured leaves on the bottom of the plant. 2,4-D choline and the other 2,4-D products are systemic. That means that if it touches anywhere on the plant, it will move throughout the plant and can cause symptoms down to the crown up to the new meristem.

So, you know it can move throughout the plant from the top to the bottom to the roots. And so, I had a little bit more anxiety that if I spray this and we have those, you know, we talked about how blackberries kind of push up in the row middles. Well, what if one of those little, you know, new primocanes intercepts this herbicide that I spray? Am I going to start to see bad symptoms there, even though it wasn’t contacting the blackberry canopy. And I was pleased that that did not happen, right? There were some symptoms. I said, you know, there was a degree of, really, really mild symptoms and for brief periods.

But the overall canopy looked very healthy. And of course, the weed control was excellent. You know, you know, it’s a, it’s not a surprise, but it was pleasant because we had to compare it to a plot that we weeded by hand. And my staff were the ones who would say they were pleased by the performance of the chemistries because that’s just less time that they’re spending, you know, hoeing weeds as opposed to, you know, just using the chemistries.

[17:24] Jenifer
And for these two trials, you also mentioned this earlier, but who were your collaborators on this trial, in this research?

[17:31] Matt
You know, this research was supported by the IR-4 program. Roger Batts is the director of the I-R4 program based out of North Carolina State. Wayne Mitchum, also in North Carolina. He’s a scientist, a grower. He is very, very familiar with blackberry production. And then the industry tends to lump blackberries and raspberries into one category called cane berries because of their growing behavior. So, the raspberries were investigated in Oregon State by Doctor Marcello Moretti. He was also doing complementary work with these materials.

[18:08] Jenifer
Very good. Is there anything else about this research you’d like to mention that I didn’t ask?

[18:13] Matt
I will say this is some of my favorite and most exciting research. I get calls about this all the time because people saw the results. We did this at Blackberry Field Day, and they said, “It looks great. When can we use it? When can we use it?” And so, I’m very excited to do this type of work that growers are excited about, you know, implementing and using on their farms. It makes me frustrated as I wait for that federal registration to be secured. I wish our government would move along a little bit quicker, but I understand that there’s a whole number of people up the pipeline doing different processes. But, it’s very promising because I know that I have good news to deliver, so that’s always exciting. I had, you know, a good discovery and I’m just waiting to tell people, you know, go forth and spray.

[18:59] Jenifer
Do you have any idea when you might get that green light or just based on other research in the past, how long this process typically takes?

[19:10] Matt
So, we finished up this trial in 2023 and compiled it. You know, I was hopeful to have it ready for the 2024 growing season. I’ve not, you know, I check pretty regularly. I’ve not seen any movement on that. So, I would anticipate by the time it’s needed in the 2025 growing season, I’ve got my fingers crossed. I can start telling people, because I want to update all of our statewide recommendations to tell people, if you’re a blackberry grower, you know, here’s the product that is listed 2,4-D, and you can use it at this rate at this timing. And if you want to glufosinate, here’s how to safely use it. Because we’re ready to put those recommendations out there. We have data to tell people how to use it safely. It’s just a matter of can they do it legally.

[19:54] Jenifer
You’re just waiting for that approval. You’ve got the data to prove that it works and it’s safe. That’s right. Yeah. That is some good news for the industry. Matt, thank you so much for being here with us.

[20:03] Matt
Sure. Yeah. Thanks for having me.

[20:06] Jenifer
That was Dr. Matt Bertucci, assistant professor in the horticulture department, talking to us about one of his recent reports on different “new” herbicide use for weed management in blackberry. Thanks for listening. I’m Jenifer Fouch. Don’t forget to subscribe.

[20:24] Intro/Outro
The Arkansas Food, Farms & Forest Podcast is produced by the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas System Division of Agriculture. Visit aaes.uada.edu for more information.