Expect to plant dicamba- or 2,4-D-resistant crops this year? Make sure you use the correct spray nozzles. From now on, not just any nozzle will do.







The label for a new dicamba formulation for the Xtend weed control system has only one approved nozzle for use in 2017, an air induction nozzle from TeeJet, although more nozzles are expected to be added prior to the 2017 season. In fact, the label for over-the-top applications of a new formulation of 2,4-D in the Enlist weed control system lists nearly two dozen nozzles from six companies.

What do all these nozzles have in common?

All are designed to create larger spray droplets to mitigate drift. The focus on nozzles comes from concern that new formulations of dicamba and 2,4-D can cause significant damage if they do drift.

“The new formulations are much better on reducing volatility, where products may turn into a gas and leave the field hours after an application in certain environmental conditions,” said Larry Steckel, Extension weed scientist at the West Tennessee AgResearch and Education Center in Jackson, Tenn.

“But the new formulations can still physically drift. That’s the reason for the regulations on sprayer speed, the nozzles, the wind and the boom height. If you produce small fines (droplets) of dicamba, and it gets on somebody’s garden, they’re going to see (damage) at ultra-low rates, which we never saw when we were spraying glyphosate.”

Steckel says a drift rate of one-eighth of a quart of glyphosate “will cause 20 percent damage to susceptible vegetation, but you get 20 percent damage at one-fifteen-hundredth of a pint of dicamba. That’s a game changing difference.”

This is also why the label prohibits spraying of dicamba (XtendiMax) and 2,4-D (Enlist Duo), in conditions favoring volatility, even though the new formulations reduce it.

“That one-fifteen-hundredth of a rate of dicamba can sure hurt a soybean variety that is not tolerant,” Steckel said.

With this in mind, Steckel and WTREC post-doctorate research associate Garret Montgomery offer these ten tips on nozzle selection and use this year. More complete information can be found on the XtendiMax and Enlist Duo herbicide labels.

#1. Different herbicides, different nozzles.

Steckel and Montgomery have been running tests over the last few years comparing various nozzles for use with contact herbicides like Liberty, Gramoxone and Flexstar and with systemic herbicides like dicamba and 2,4-D.

So far, the research shows that TTI air induction nozzles, including the one approved for Xtend systems, do not perform satisfactorily with contact herbicides. For many producers, this means the end to a “one-size-fits all” approach to nozzle selection.

#2. Approved nozzles are a requirement, not a suggestion.

For the dicamba-brand called XtendiMax, only the TTI 11004 (air induction) nozzle with a maximum operating pressure of 63 pounds per square inch is approved as of this writing (mid January, 2017). As more nozzles are approved, they can be found here.

The label for Enlist Duo, which contains glyphosate and 2,4-D, lists 23 approved nozzles at time of publication. Not all of the nozzles listed on the label are air induction types. Brands include ABJ Agri, Greenleaf, Hypro, Lechler, TeeJet and Wilger.

Nozzles not listed cannot be used.

#3. Don’t procrastinate. Buy nozzles if you need them.

Steckel recently asked a group of producers how many of them had purchased TTI nozzles for the coming year and nobody raised their hand. That’s unsettling to Steckel.

“If there are going to be 40 million acres of Xtend crops, will we have enough TTI nozzles? I don’t know,” he says. “But I’d rather producers get them sooner than later.”

Tim Stuenkel, marketing manager for TeeJet Technologies, agrees. The company is putting additional tooling in place to accommodate what could be significantly increased demand for its TTI 11004 nozzle, but Stuenkel adds, “We do encourage producers to get their orders in early.”

The nozzle package for Enlist Duo application is a little different, noted Steckel. “There are more nozzles to choose from and you don’t have to have the TTIs. The AIXR nozzles, which many producers are using today, are on that label.”

#4. Droplet size matters.

The approved nozzle for Xtend systems produces a droplet size of around 650 microns. Enlist Duo allows for a smaller droplet. A 650-micron spray droplet is between the thickness of a common staple and a paper clip.

The smallest micron size particle seen by the human eye is around 40 microns. The eye of a needle is around 1,200 microns.

#5. Don’t get too hung up on coverage.

Dicamba and 2,4-D are systemic herbicides, so you don’t need to cover the entire weed with small droplets to kill it. “You need just a few droplets to get the herbicide into the plant and it’s going to move once it gets in there,” Steckel said.

#6. Watch your speed.

Droplet size is affected by operating pressure, so it’s important to keep the spray rig at the proper speed. “A rate control system will push the pressure up as you go faster,” Montgomery said. “The more pressure you have, the smaller the droplet size.”







Slower speeds generally result in better spray coverage and deposition on the target, as well.

#7. Consider a turret system for your sprayer.

Legal applications will mean that you will likely change nozzles more frequently during the season. Steckel and Montgomery suggest a turret system for nozzles, which could save time.

#8. Consider dual nozzles.

“Anytime you have nozzles spraying in different directions over the same row, the spray is going to hit more places,” Montgomery said. “The only way you can lose some control with a TTI nozzle is if weeds are so small you’re not hitting them.”

With dual nozzles, each nozzle can run on less pressure, Montgomery says, which is good for maintaining an optimum droplet size.

#9. Don’t use a pulse width modulation system on your sprayer when using an air induction nozzle.

“An air induction nozzle like the TTI works best when there is

constant pressure,” Montgomery said. “There are companies working on nozzles that work with pulse width modulation systems that put out the same droplet size as the nozzles that are approved, but nothing has been developed yet.”

#10. Practice stewardship.

“We definitely had our mulligan last year,” Steckel said in reference to illegal dicamba applications made in parts of the Midsouth in 2016, which led to numerous drift complaints and investigations. “We have to follow all the rules and use formulations that are going to stay put after the spray. It’s not going to be a low-maintenance application.