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Dicamba challenges and opportunities

Article cover photo
A 90-foot 645 Redball --- Hooded Sprayer in-use recently in a Minnesota soybean field. (Submitted photo)

By Matthew Wilde, ISA senior writer


The Iowa Department of Agriculture and Land Stewardship (IDALS) urged pesticide applicators this week to take necessary steps to prevent drift as dicamba injury reports trickle into the agency.

Plastic spray hoods, widely-used for decades in southern cotton fields but not in Iowa, may help increase the odds of on-target application. While hoods won’t stop drift due to volatilization (herbicide turns to gas after application), manufacturers say they do help prevent physical drift from wind and bolster uniform coverage.

New low-volatile formulations of dicamba, which can be sprayed over-the-top of soybeans engineered to tolerate the herbicide, debuted commercially last year. Farmers nationwide reported excellent weed control, but varying levels of damage to millions of acres of nontolerant soybeans and other sensitive off-target plants occurred. Drift, volatility and applicators not following label instructions were the primary culprits, according to industry and government officials.

IDALS has received two dicamba injury complaints as of June 22. However, agency spokesperson Dustin Vande Hoef expects the number to increase as the spraying season continues.

To minimize potential damage, Iowa Secretary of Agriculture Mike Naig encourages farmers and applicators to follow chemical label requirements. Evaluating wind speed and direction, temperature, humidity, spray pressure, nozzle height and following setback requirements are essential before spaying, he said.

“The recent wet weather has created some challenges as farmers and applicators look to spray for weeds and pests, but it is important they wait until conditions are right and that they carefully follow all the product label requirements,” Naig said in a statement. “Pesticides are important tools that help keep our crops healthy and it is important that they are used appropriately and do not impact neighbors.”

Records indicate IDALS conducted 110 dicamba-injury investigations last year. More than 100,000 acres, mostly soybeans, were affected, according to Iowa State University (ISU) estimates. Nationwide, more than 2,700 dicamba-injury investigations were conducted covering 3.6 million acres of cropland, according to published reports.

Bob Hartzler, ISU Extension and Outreach weed scientist, estimates 1,200 acres of non-tolerant crops statewide have sustained damage from dicamba so far. He reported the number to Kevin Bradley, a University of Missouri weed scientist, last week.

Bradley compiles nationwide dicamba-injury statistics every two weeks for the U.S. Environmental Protection Agency (EPA). It will determine whether to allow over-the-top use of dicamba beyond the 2018 growing season.

“Most Iowa complaints so far are in the southeast, where soybeans were planted earlier and herbicide applications have wrapped up or are wrapping up,” Hartzler said. “But some beans were planted late (especially in northern Iowa) and applications could continue through mid-July.

“We have no clue how things will go this year — hopefully well,” he continued.

In Iowa, dicamba can be sprayed up to and including the R1 development stage (beginning bloom) per label instructions. Four percent of Iowa’s soybean crop is blooming as of June 24, according to the U.S. Department of Agriculture Iowa Crop Progress and Condition Report.

If Iowans have a concern about a specific pesticide misuse incident, they can file an “incident report” with the IDAL’s Pesticide Bureau by calling (515) 281-8591 or by emailing the information to

Reports must be filed within 60 days after the alleged date that damages occur.

A farmer uses a 40-foot 642E Redball --- Hooded Sprayer to apply herbicides to a soybean field adjacent to corn recently in Minnesota. (Submitted photo)

Hooded sprayers

BASF and Monsanto teamed up with Willmar Fabrication to offer incentives, including thousands of dollars in rebates and discounts, on the purchase of qualifying Redball — Hooded™ Sprayers with their respective dicamba herbicides. The central Minnesota company — — makes hooded three-point-hitch sprayers and hoods for self-propelled sprayers.

The poly structures, with attached flexible wind curtains, brush the soybean canopy during spraying. Hoods protect the spray pattern and help prevent droplets from escaping into the atmosphere.

“I can’t guarantee no drift, but you can all but eliminate drift caused by the wind,” said Steve Claussen, Willmar Fabrication owner.

That doesn’t mean farmers can ignore herbicide labels. Dicamba can only be sprayed when the wind is between 3 to 10 mph.

Redball hoods — ranging from 10 to 100 feet depending on the sprayer — increase the chances of on-target applications and provide better coverage than open booms, Claussen said. However, hood length is a limitation if a farmer has a 120-foot sprayer and extra clean-out time may be required.

Claussen believes his products can benefit farmers who are worried about damaging neighboring crops and sensitive areas while spraying any chemical.

“We need to control movement to preserve the use of chemistries,” Claussen said. “Hoods are like an insurance policy.”

The company is working with regulators to allow certain herbicides to be applied at higher wind speeds if Redball hoods are used to increase spraying windows. It conducted field trials at the University of Nebraska and Mississippi State University studying drift at different wind speeds comparing open and hooded booms.

Claussen believes sales will soar as applicators learn about Redball hood effectiveness.

“We have something we know that works,” he said.

Reball — Hooded Sprayers and hood attachments for self-propelled sprayers range from $4,000 to $60,000. Claussen plans to showcase products at the Farm Progress Show in Boone, Aug. 28-30.

Ed Anderson, Ph.D., Iowa Soybean Association senior director of research, said weed management is critically important to soybean production. This is especially true as farmers continue to adopt improved cropping systems and agronomic practices like reduced tillage and no-till, he said.

Herbicide-resistant weeds present ongoing challenges. Farmers must have as many tools as possible to develop integrated weed management programs for their cropping systems, Anderson said. 

“For herbicides that demonstrate a drift concern, farmers may wish to consider evaluating sprayer hoods as another potential safeguard against drift to off-target plants,” he continued.

The opportunity for testing hoods on specific on-farm trials may benefit farmers going forward, Anderson said.

Contact Matthew Wilde at

For media inquiries, permission to republish articles or to request high-res photos, please contact Katie James, ISA Public Relations Manager at © 2020 Iowa Soybean Association. All rights reserved.

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