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Farmers need to approach 2017 crop spraying season very carefully

Conventional wisdom says that if EPA will approve registrations for the new dicamba formulations that are planned for use on Roundup Ready Xtend Crop Systems in 2017 most of the problems with off-target applications will go away.

Kevin Bradley – along with other university weed scientists – isn’t so sure about that, as Bradley, a University of Missouri Extension specialist, explained to farmers attending the 55th Annual Fisher Delta Research Center Field Day in Portageville, Mo.

“I’ve come out publicly numerous times against all the advertising and the marketing that says you won’t have these problems in the future because we have these new formulations,” he said. “I don’t know that that’s true. We’ll see. Maybe I’m totally wrong, but we’ll see.”

Dr. Bradley says the Missouri Department of Agriculture currently is investigating off-target application complaints on 40,000 acres of soybeans, most of them in southeast Missouri where Portageville is located. “Realistically, the number is twice that if not more. A lot of farmers don’t want to turn it in, and I completely understand that.”

Although Bradley is based on the University of Missouri-Columbia campus, he said he’s probably spent two or three days per week in southeast Missouri (the Missouri Bootheel) since the complaints began to surface about six weeks ago.

‘Almost everything y’all grow’

“Just about everything y’all grow down here has been injured in some areas,” he said. “There’s 700 acres of peaches y’all have probably read about. It’s a bad deal, and it’s given us a black eye. It’s not just the Bootheel, but there is another area where this sort of things has happened in north central Missouri that I’m also working with.”

Dr. Bradley said he’s heard and read numerous reports the new formulations that are awaiting EPA approval will solve most of the off-target issues.

“I don’t have the confidence to be able to make that statement,” he said.

USDA has approved the Xtend trait – which confers resistance to dicamba herbicide – in both cotton and soybeans so both could be planted in 2016. EPA has not approved any formulation of dicamba for application on Roundup Ready Xtend Crop Systems.

“The problem is EPA approves the herbicide, and the EPA til this day still has not approved any dicamba product for use in Xtend crops,” said Dr. Bradley. “That is a big part of the problem, though it is not the only part of the problem.

“If we’ve learned anything, in the future, I hope we never go again with some trait without having the corresponding herbicide to go with it at the same time. It’s not the only reason for the problem, but it’s a big part of the reason.”

New formulations under EPA review

The basic manufacturers have developed two new formulations of dicamba that promise to be less volatile than Banvel, the oldest formulation of the herbicide. But neither formulation, by itself, will eliminate the problem of drift, according to weed scientists.

“So what can we do?” Bradley asked. “Assuming everything gets approved, and next year you want to grow Xtend soybeans, and you don’t want to hurt any of your neighbors, you don’t want to drift on anybody or have any movement. So what can you do?”

The first step, he says, is to “understand that even extremely low, low doses of dicamba will cause injury to surrounding crops that are sensitive to it, mainly soybeans. If I can summarize what has happened this year, it is a misunderstanding of how very, very low doses of dicamba will cause injury. One two-thousandth of the normal use rate if it gets on other people’s soybeans will cause yield loss.”

Many farmers would go out on a day like the day the Delta Center Field Day was held (a day which was unusually cool because of a northerly breeze) and spray glyphosate without injury to other crops, Dr. Bradley noted.

“That ‘s not going to be the case with dicamba. So we’ve got to get used to that change. Second to that is we have to apply with the right nozzles that will produce coarse droplets. We have to keep our spray booms down – there are so many booms that are way up in the air. We have to be aware of the potential for drift on days like this. We have to be aware of what volatility is and what temperature inversions are.”

Temperature inversions can cause movement

Bradley says he believes some of this summer’s complaints were due to farmers spraying into temperature inversions, which caused dicamba to move miles away from the intended targets of the applications.

Temperature inversions can occur when a warmer, less dense air mass moves over a cooler, denser air mass, creating a situation in which the air is colder rather than warmer nearer the surface of the earth.

“Condition for a temperature inversion are not what we’re seeing today,” said Dr. Bradley, referring to the winds pummeling the tent where he was speaking. “But they are what a lot of us would think of as a good time to spray.

“For example, later towards the evening the winds die down. There’s hardly any wind at all. No cumulus clouds showing up. Those are all signs we’re likely entering into a temperature inversion. They typically occur later in the afternoon, throughout the night into the morning. We generally don’t see a lot of them between the 10 a.m. to 3 p.m. timeframe.”

What does happen between the 10 to 3 time frame is the peak wind gusts, which can lead to drift problems for spray applications.

“When there is no wind, that’s a bad time to be spraying,” he said. “It doesn’t sound right, but almost certainly if it’s a completely calm situation toward the end of the day, you’re probably experiencing a temperature inversion. All that means is there’s no mixing of air; there’s cool air trapped beneath some warm air.

“You have this stagnant air mass, and we spray into that and many of those particles get suspended and never reach their intended target, And what happens is they fall or settle out, and it can be miles away when that occurs. I believe several of the fields I’ve looked at in this area this year had off-target movement as a result of that happening.”

For more information on the field day, visit

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