3 Reasons Iowa Farmers are Seeing More Dicamba Damage

Farmers and applicators are seeing more dicamba damage in Iowa this year. ( Lindsey Pound )

Pressure is mounting for dicamba products. Manufacturers are seeking 2021 and beyond registration, meanwhile off-target damage is reaching high levels. According to experts at Iowa State University Extension, the state is seeing the most extensive damage since the 1960s when the herbicide was first introduced.

“This is not the type of injury we have observed in the past: it’s at a landscape level,” says Bob Hartzler, Iowa State University Extension weed scientist in a recent blog post. “Field agronomists and commercial agronomist in several areas of the state report nearly all non-dicamba resistant soybean are showing symptoms characteristic of dicamba, and in many fields the injury is fence row to fence row.”

The issues relating to this off-target movement can’t be blamed on one single application method or error, Hartzler adds. It’s a variety of things that have contributed to 2020’s problems.

  1. An untimely court decision. June 3, 2020 the U.S. Court of Appeals for the Ninth Circuit vacated the registration of three of the four over-the-top dicamba products. This was prime time for post applications for many farmers and applicators, who were left in limbo until EPA issued a ruling. “It is likely that some applicators made poor decisions regarding appropriate application conditions based on fears dicamba would be made unavailable for use in 2020,” Hartzler says.
  2. Environmental conditions. Because Iowa had stellar planting conditions, corn and soybeans were both ready for post-herbicide applications at the same time, creating overlap in dicamba applications to corn and soybeans. In addition, weather conditions and wind did not cooperate with applicators to make for easy dicamba applications. “Weather conditions limited opportunities to get fields sprayed, resulting in large quantities of dicamba being applied in a small time period,” Hartzler adds. “Limited rainfall during this period left dicamba on soil and foliar surfaces for extended times where it is prone to volatilization during hot periods.”
  3. Use on corn. Farmers and applicators have increased dicamba’s use on corn to combat problem weeds such as waterhemp, which confer a high level of resistance. “Nearly all of the dicamba products used in corn are formulation higher in volatility than the formulations registered for use in dicamba resistant soybeans,” Hartzler says. “Dicamba use in corn also have a lot of flexibility in terms of drift reduction practices compared to the unprecedented restrictions placed on dicamba use in soybean.”

Regardless of the court’s decision, Hartzler says damage would have still been a huge problem with the way this season turned out because of other conditions. Widespread damage is problematic for not only the farmers who received damage, but potentially the future of the product, too.

“Continuing down this path will only result in more restrictive rules for dicamba and other pesticides,” he says. “Herbicides will continue to be the backbone of agricultural weed management for the foreseeable future, but they need to be used as part of an integrated management program in order to protect their effectiveness and reduce negative impacts to the environment.”

BASF provided the following statement to AgWeb (7/9 11:00 a.m.) in response to these claims of increased off-target damage:

Herbicide application season is still underway in many of the Midwest’s most productive soybean producing states, including Iowa. Our Field Team continues to work directly with growers and commercial applicators to support on-target applications of Engenia herbicide as allowed by the EPA’s cancellation order and we will investigate any incidents submitted to BASF. So far in 2020, BASF has only received two off-target incident reports for dicamba containing products. At this time last year, we had no such reports. We never compromise on safety and provide tools that allow for the responsible use of our products. When Engenia herbicide is applied in accordance with the label, it has been found to produce safe, effective and on-target applications.

Read more about recent lawsuits:

Dicamba’s Future is Shaky—Is Enlist Next on the Chopping Block?

BREAKING: Court Removes Three Out of Four Dicamba Registrations