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Cupped soybeans Bill Johnson, Purdue University Extension weed specialist

BASF: Nozzle choice led to dicamba drift

BASF researchers talk about what it takes to make applications successful without off-target movement.

Reports of dicamba drift across the country led Farm Progress editors to seek out information from companies who make new herbicides. BASF accepted the invitation.

Dan Westburg, BASF technical service manager for the Crop Protection Division in the Delta, and Gary Schmitz, BASF technical service manager for the Crop Protection Division in the Corn Belt, provided insights about what they’ve seen and learned so far during the inaugural season of use of their dicamba product, Engenia, on dicamba-tolerant soybeans. 

Broad scope
Here is information provided by Westburg and Schmitz as it relates to Engenia on dicamba-tolerant soybeans, with an emphasis on the Midwestern states.

  • Observations in the field. Both Westburg and Schmitz say that someone follows up on every call from a grower with a problem. Both have spent considerable time walking fields and talking to farmers, custom applicators and herbicide retailers.

The calls tend to fall into two broad categories, they note. In some cases it’s easy to determine that the problem was caused by physical drift, Westburg says. Wind speed and direction were often involved. The second general category consists of situations where whole fields are affected uniformly, but where the cause is not readily apparent. It’s often classified as “undetermined” until more investigation is possible. 

The second category seems to break itself into two more categories. In some cases the spray equipment wasn’t cleaned properly, resulting in contamination. But in other cases, especially where the application was made at night, temperature inversions seem to be the culprit, Westburg says. He notes that both spraying at night and the tendency toward temperature inversions are more frequent in the Midsouth. However, Schmitz says temperature inversions are also proving to be an issue in the Midwest.

  • Temperature inversions. “It’s likely the least understood of weather phenomena, but it definitely plays a role,” Schmitz says. “It occurs when there is cooler, denser air near the ground. When fine spray particles become suspended in the inversion, they can move. It’s impossible to predict exactly how they will move.”

Schmitz offers these practical ways to detect when a temperature inversion can occur.

First, there will be little or no wind. The air is calm. Second, late in the evening you may notice fog developing, especially in low-lying areas. Third, if you live along dirt or gravel roads, dust from the road tends to hang in midair. Fourth, if you’re in hilly terrain and you drop down into a valley in the evening, it will seem cooler.

The Engenia label specifically prohibits spraying when a temperature inversion occurs. But what if you spray during the day and an inversion happens that evening? Are you still at risk for movement?

“By evening, spray particles from the daytime application should have already hit the ground,” Schmitz says. “Once they hit the ground, there shouldn’t be an issue even if an inversion develops that evening.”

  • Nozzle selection. “This is absolutely critical,” Schmitz emphasizes. “Outside of wind speed and environmental conditions, it’s the No. 1 factor that determines if you’re likely to see off-target movement.”

Why is it so critical? Because conventional nozzles like flat-fan nozzles create droplets with a wide range of particle size. “With some of the older nozzles, 30% to 40% of the particles might be fines,” Schmitz says. “Those are the ones subject to drift if it’s too windy, or likely to be caught up in a temperature inversion.”

Newer nozzle technology typically provides much more consistent droplet size. For example, with Turbo Tee Injection nozzles, one of the types approved for Engenia application, droplets tend to be large to medium-sized. Some call these ultra-coarse droplets. The amount of fines drops to about 1%.

“But 1% isn’t zero,” Schmitz acknowledges. “So we still need to pay attention to wind speed and other environmental conditions.”

  • Nozzle give-away program. BASF felt so strongly about the need to use the right nozzles, that it offers nozzles suited for Engenia application free to growers. “We’ve given away about 600,000 nozzles so far,” Schmitz says.

So if the nozzles are free, why is anyone spraying with nozzles not approved for dicamba application? “We’ve found that some farmers are worried about getting adequate weed coverage,” Westburg says. “They’re concerned that the droplets are too coarse to get good coverage, so they go back to nozzles with smaller droplets. That can lead to problems.

The truth is that since Engenia is absorbed by the plant, you don’t need the coverage you need for a contact herbicide, he explains. “It’s part of the education process that we’re doing, and still need to do,” he says. 

  • Drift vs. volatility. Engenia uses a unique dicamba salt that is much less prone to volatilize, Westburg says. “Part of the confusion this season is that when growers can’t figure out why an entire field was affected, they think it must be because the product volatized and moved,” Westburg says. “We’re confident after being on many of these calls, that what’s really happening is that fine spray particles are caught up in a temperature inversion. That’s still drift, not volatilization. The catch is, as noted earlier, there is no way to predict exactly where those particles will wind up.”
  • Education programs. About 15,000 applicators so far have completed BASF’s On-Target Application Academy. It’s a one- to two-hour program of face-to-face training, which prepares growers to apply Engenia according to the label. “We’re hoping to expand OTTA training later this year and into the winter,” Schmitz says. “There is also a web version, but we recommend growers do face-to-face training if at all possible.” Check the BASF website for information about how to find when this training will be held in your area.
  • Look to the future. “Growers need these products,” Westburg says. “In the South, we battle glyphosate-resistant Palmer amaranth, and some is now PPO-resistant as well.

“Liberty is the only other alternative right now. If growers continue to rely on Liberty to get these resistant weeds, it won’t last very long. Engenia is another tool in the toolbox that growers desperately need.”

Both Westburg and Schmitz note that they will take what they learned this season and adjust training programs and recommendations for next season. The learning process is still going on right now. Applications are still happening, and calls about issues are still being investigated.

“We’re going to do all we can to make sure growers use it properly and see good results going forward,” Westburg concludes.


TAGS: Soybeans
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