Research work evaluates various herbicide applications

SEYMOUR, Ill. — The first herbicide application in a field impacts the crops throughout the growing season.

“It could be the difference between getting off on a good start or having to come in and clean up a mess that could derail the program for the rest of the year,” said Mike Probst, BASF technical service representative.

“We know a vertical tillage tool pass is not going to control weeds,” said Probst during a presentation at a BASF Field Day, held at the BASF Midwest Research Farm in Seymour in east-central Illinois.

“So, that grower may need to make a burn down herbicide application to start off with his field clean,” he said. “We recommend you do your burndown herbicide application and wait a day or two before making your tillage pass.”

Probst often gets questions about incorporating residual herbicides. He talked about the difference between two plots.

One was sprayed with Zidua SC at a full rate and then worked with a field cultivator four to five inches deep. For the second plot, he made a tillage pass and then sprayed it with Zidua SC.

“When we make tillage passes and incorporate the herbicide into the soil, it breaks up the layer of herbicide concentration we ideally want to keep in the top layer of the soil,” he explained. “Waterhemp emerges in the top one-quarter to half inch of the soil.”

“When we distribute the herbicide across a five-inch layer in the soil, we’re taking a lot of that herbicide below the germination zone where it won’t have as much impact,” he said. “That’s why we like to see the residual left undisturbed on top of the soil versus being incorporated in with tillage.”

When a farmer has a poor stand of corn and wants to replant it, Probst has been asked if the corn can be killed with an application of Sharpen.

“We sprayed three ounces of Sharpen with AMS and MSO and the corn looks bad, but Sharpen is a contact herbicide so it has a hard time killing the growing point,” he said.

The corn was sprayed at V4.

“This corn plant is looking pretty rough, but you can see new growth starting to emerge,” Probst said. “This plot has about one to two days of looking really bad and after that it’s probably going to start to look better.”

A lot of spraying recommendations are determined by whether the herbicide is a contact or systemic herbicide.

“A contact herbicide is going to kill what it comes in contact with,” Probst said. “Nozzles will drive the coverage.”

Systemic herbicides move throughout the weed to do their job.

“They don’t rely as much on coverage to get their control,” the BASF representative said.

Probst discussed a plot where he looked at right versus wrong combinations of nozzles and carrier volume.

“Here we have TTI nozzles and we sprayed at 10 gallons per acre,” he said. “The TTI nozzles are extra course to ultra course droplet sizes and that is mainly focused on keeping the herbicide on the field where it is sprayed and not towards getting the maximum coverage.”

“When we combine that with half of the carrier volume we recommend for Liberty ULTRA, we’re starting out with a couple strikes against us,” he admitted. “This combination got us 25.8% coverage which is not very good for a contact herbicide.”

When Probst doubled the carrier volume, that almost doubled the coverage, as well.

“We went from 25% to about 46%, but this still is not what we’re striving for,” he said. “You can see with these very large droplets, our droplet distribution is not where we want it to be.”

There is a lot of product where the droplets hit.

“But we’ve got a lot of misses here so you could have small waterhemp seedling fit in a lot of these gaps,” Probst said. “You can’t do just one of the things right — we need both of them done correctly if we want to give ourselves the best chance for control.”

“When we switch to the correct nozzles like these TT nozzles that give you a medium to course droplet size, things look pretty good,” he said. “We got about 43% coverage, but we’re still not maximizing our control.”

With the ideal scenario of 20 gallons per acre and Turbo Teejet nozzles, the coverage was over 50%.

“We don’t have large spots next to small spots where a waterhemp seedling can make it through,” Probst said. “This is a much more uniform distribution.”

The time of day is another important consideration for herbicide applications.

“Our data clearly shows the level of control goes in a bell curve,” Probst explained. “In those early morning applications, we’re not getting the control we want, as we wrap up towards the middle of the afternoon the control starts to peak and as we go into the evening hours of 7 or 8 p.m., the control starts to drop off again.”

“Try to avoid those early morning and late evening applications for Liberty spraying,” he stressed.

“Probably once a year I get the question from a farmer who sprayed Zidua PRO because he was going to plant beans and now he wants to plant corn, so can he plant corn?” Probst said.

“The answer is no, because Zidua PRO is not labeled pre-emergence for corn,” he said. “Stunting is usually the big concern, and since corn loves consistency, it needs to grow at the same pace to reach its maximum potential.”