By Brian Hefty

I have been an agronomist for over 25 years, and I’ve never seen anything like what we’ve experienced this summer in terms of leaf cupping on soybeans. I have cupped beans, too. While this is an emotional issue, it’s always best to take the emotion out and look at it from a business perspective. Here are some of my current thoughts on this issue.

On the plus side, Xtend soybeans look great. On average last year, our Xtend beans beat our Roundup 2s by 1 to 2 bushels in multi-location, multi-state trials. The burndown for no-till and strip-till guys was great. Marestail and all other weeds died at that time. It has also been nice to have a post-emerge weed control option for kochia, marestail, waterhemp, and other tough, Roundup-resistant broadleaves. From all the thousands and thousands of acres of cupped beans I’ve looked at, in my opinion, most of those fields won’t suffer yield loss. Certainly, a bunch of them will, but even if there was zero yield loss on any field, we can’t have millions of acres of soybeans cupped next year. This has been ridiculous. By the way, from what I’ve seen, almost no other plants have been cupped in most areas. I used to think sugarbeets, sunflowers, and tomatoes were as sensitive or more sensitive than soybeans, but they apparently aren’t. I’ve seen those crops look perfect right next to cupped soybeans.

So what’s the real cause of the problem? Certainly, there are cases of incorrect usage, improper spray tank clean out, and spraying when it has been way too windy with no downwind buffer. I’ve also heard a lot of excuses. It’s too hot. It’s unlabeled product. The spray droplets are too small, etc.
In my opinion, and at this point, this is just my opinion, so please don’t think we have made our final conclusions on this, but I don’t think any of the “excuses” are correct. Here’s what I believe is happening – we’ve made the droplet size too big AND put so much stuff with it, that dicamba isn’t getting absorbed into leaf foliage as quickly as it used to. Because of that, it has more time to volatilize and move off-target many hours later. This problem is greatly accentuated with evening and night spraying, due to temperature inversions.

What should be done going forward? First of all, Xtend beans are going to be here in 2018. How the chemistry is used and labeled is the only question. Keep in mind, too, that stacks are coming, possibly as early as next year. In other words, by the 2019 growing season, you may be able to have a Roundup/Liberty/Xtend bean on your farm. That would eliminate most of the issues, because you could use dicamba for burndown and very early season followed by a late shot of Liberty. Keep in mind that right now, Liberty is labeled up to R2, while dicamba is only labeled to R1 in their respective crops.

If my theory is correct, and we’ve made leaf absorption take far longer than it should, it seems only logical that there are 3 possible solutions. One, ban post-emerge usage or have a cutoff date of say June 15 – before any soybeans are flowering. For all the farmers with major weed issues, they’re not too excited about that. We don’t believe there are even half as many Liberty beans available as needed if the entire country switched to LibertyLink.

Two, allow dicamba spraying only between 4 hours after sunrise and 4 hours before sunset (or some variation of that). From what I’ve seen, most of the off-target movement has happened overnight or the next day when the wind shifts. By spraying mid-day, when it is hot and sunny, you get much faster absorption. Even if the product moves, you know what direction it will move because you know what direction the wind is blowing when spraying.

Three, increase leaf absorption. If we go back to smaller droplets and no drift retardant, there will be faster leaf absorption, meaning there will be less time for volatility and off-target movement. Yes, this means I would suggest increasing the downwind buffer, but I’ll happily trade away the current volatility problems we’re seeing for drift. As a farmer, I feel I can manage drift, but I have no control over volatility. By the way, I’ve also had it suggested to me that we’re not seeing volatility. It may just be that the droplet is landing on the leaf, not getting absorbed, and then blowing away with the wind. I don’t believe that, but even if it was true, leaf absorption is still the problem. By the way, if we increase leaf absorption, that will mean better weed control, too. This year, weed control with dicamba was sub-par, primarily because the droplet size was gargantuan.

I have been around dicamba my whole life. I wasn’t too worried about issues this summer, because I’d had virtually no volatility issues in my entire career, after personally recommending tens of millions of acres of dicamba applications. We’ve somehow screwed up dicamba. It’s not as bad as it looks this summer, but if we can’t get the problem figured out, and quickly, summer spraying of dicamba is going to get banned. In my opinion, we need dicamba as a post-emerge weed control option, and I think we’ll get it figured out.

Regardless of what happens next year with labeling, I would encourage you to talk to your neighbors so you know whether or not they have Xtend beans. If they do, great. If they don’t, be extremely cautious, because even if you don’t hurt yield with leaf cupping, no one likes to see that.

If you had a volatility issue this summer, please do not think I’m taking this issue lightly. I had an issue, too, and I’m not happy about it. Something needs to be done, and I’m confident something will be done. In the meantime, let’s see how yields turn out this fall. While I have had to deal with almost no volatility issues with dicamba like we’re experiencing this summer, I’ve dealt with lots of dicamba physical drift issues. In my experience, shortening the beans with dicamba usually leads to some amount of yield loss, but leaf cupping only rarely does. We will see how it turns out this fall, and I’m anxious to find out about label changes that should be coming this winter.