CropLife chatted with Ryan Wolf, Western Agronomy Services Manager with WinField United, on field testing he conducted that showed less is definitely not more when it comes to the gallons of water per acre to use with dicamba products. He also shared some interesting findings about why you should avoid certain drift reduction agents (DRAs).
CL: What were your trainings like over the winter?
I’ve been giving presentations all over on what we learned from 2017 going into 2018. WinField United does spray clinics. We either did it in conjunction with BASF or Monsanto training, or we did it by ourselves at retail accounts and dealers. We’ve been talking about dicamba specifically, but also talking about things we’ve learned going into 2018 that you’re not going to hear at some of these trainings.
CL: What wouldn’t we hear at the other trainings?
The XtendiMax label went from 10 gallons minimum coverage per acre to 15 gallons this year, and Engenia is still at 10 gallons per acre. But we’re telling our dealers (to apply) 20 gallons per acre, and guys who did that got better coverage on small carpet weeds like kochia, and waterhemp if you have a dense population. It’s way better coverage at 20 gallons per acre. We learned that early last season going into the burndown season. If we were at 10 gallons and we had some dense weeds, we had a lot of escapes.
The labels don’t have a maximum for gallons of coverage per acre. How we are spraying these dicamba products is just (comprised of) big droplets. We did a lot of in-field training last year (with the minimum gallons) with red dyes and spray booms showing holes in the spray pattern. You could literally look at an inch between spray droplets.
CL: What should the spray pattern look like?
When you’ve got small weeds, the better coverage you get means the more weeds you’re going to get. That’s why going from 10 to 20 gallons per acre doesn’t double your coverage, but it increases your coverage enough that it decreases the gaps between spray droplets.
CL: Is it common to use the minimum gallons per acre?
Yes. WinField United’s recommendation this year is to use 20 gallons per acre. The minimums are there, but use more gallons per acre, especially if you’ve got a lot of dense weed populations.
The label last year said 10 gallons minimum, so everyone went to the 10-gallon mark right off the bat, which is common on a systemic herbicide. But with the nozzle selection we’re using with that ultra- and extreme-coarse spray nozzle, we’re just not getting the coverage we’re used to.
CL: Bob Wolf was talking about how important it is to use high pressure.
That’s in our second learning (at our trainings). On the nozzle recommendation, not all nozzles perform well with the DRAs that are mandatory with a lot of the tank mixes. Choosing the right nozzle is critical with a higher-labeled pressure. A TTI nozzle goes up to 63 pounds of pressure. We would like everyone to be at 50 psi.
There are some nozzles that do not work well at all with the DRAs. We put out a tech bulletin on what are the right nozzles to be using with some of these. The TTI nozzle has probably been the best one that we’d recommend.
CL: Is there anything you saw in your training experience over the winter that made it clearer for you about what happened last year?
There are a lot of little different things. We’re actually publishing a paper this summer on pump shear.
CL: What is pump shear?
Shear pulls the product apart. It’s caused by non-uniform flow within spray lines and spray pumps.
A lot of these DRA products that got labeled are based on old polyacrylamide technology. The problem with that old technology was that it made big droplets and reduced drift – that’s great – but if you run them through the pump enough times, that product actually breaks down and makes smaller droplets. After 30 to 50 times circulation through a pump, we found out it’s just like not spraying with a DRA.
CL: Do you think this was a common cause of drift last year?
This could be some of the problem. There are multiple problems out there, and we’re all learning, but this is one problem that might have happened. With some of these polyacrylamide technologies, we had some pump shear and created fines that we didn’t know we were creating.
There are some DRAs that are polysaccharides, which are not subject to pump shear. So there is a differentiation in the industry on DRAs.
CL: Are those polyacrylamide-based DRAs still labeled this year, and is the issue not widely known?
They are still labeled, yes, and I’m sure there are more people looking into that. Most people probably don’t know about the issue. We’re trying to get the word out – like I said, we’re going to be publishing a paper on the testing we did with these DRAs.
CL: How did you guys discover this problem that could be one of the causes of drift?
We’re pretty basic in adjuvant work, especially drift control. Through our research facility and through the knowledge we’ve had in the past with polyacrylamides – I mean, this is 20- to 30-year-old technology that we’ve been using. We suspected there was pump shear involved. Now, we actually measured it and have the technology to measure it and prove it.
CL: What options are you recommending for DRAs then?
You’ve got to use a DRA, but you’ve got to be aware of the make-up of different DRAs, and you can find that information on the labels of active ingredients. If you want to learn more about it, see our tech bulletin.
Read more on the label requirements here:
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