WEST LAFAYETTE, Ind. — The policy board at the Office of Indiana State Chemist (OISC) last week took the first step to declare the broadleaf herbicide dicamba a restricted-use pesticide (RUP).

 

Unanimously passing a notice of intent to adopt a rule, the board wants to limit who can sell the herbicide and who can apply it on fields. This is the beginning of a rulemaking process that can take 6-12 months, said Dave Scott, pesticide administrator for the OISC, based at Purdue University.

 

If the rule is adopted during that period, it would apply to the 2018 growing season. As for 2017, Hoosier farmers and pesticide dealers are still under the federal law, which does not label dicamba as a RUP.

 

However, the labels for the new formulation approved this year have specific requirements for how to use the herbicide, including nozzle height, wind speed and weed height. RUPs can be sold only by dealers who are certified to do so, and they can be applied on fields only by commercial applicators and certified farmers who have taken a competency exam.

 

In Indiana, the OISC has the authority  to make rules regarding chemicals, and the rules are not subject to a legislative process, but the public still has the opportunity to comment on the rules.

 

Scott explained the policy board has studied dicamba for the past seven years. This new move by the state comes on the heels of the U.S. EPA’s approval of a new formulation for dicamba for tolerant soybeans, cotton and other crops.

 

Each state has the authority to adopt the EPA’s standard as is or add to it. He said the board is concerned about the possible misuse of dicamba this year before the state rule takes effect.

 

“We are all in agreement that it is necessary to protect the product from being misused and from neighbors and non-target clients,” Scott said. “It is very effective at low levels. If it moves off target, it can devastate high-value crops like grapes, tomatoes, vegetables, trees and shrubs.”

 

Dicamba is prone to drift in winds less than 3 mph and has high volatility, which indicates potential to move from the surface of a plant even after it has been applied. He said the board has “major concerns” that growers will use older formulations of dicamba on new resistant crops. The older formulations are labeled with fewer restrictions, which could cause problems.

 

“This is not a new herbicide, but we believe there is potential for much more widespread use and during a later growing season, when plants are at sensitive stages. Farmers need to control weeds, but we are hopeful they will use dicamba  safely.”

 

State boards and growers potentially at risk from dicamba are not the only ones raising concerns about its use. Aaron Hager, associate professor of weed science at the University of Illinois, said dicamba is not a “silver bullet technique” for controlling weeds.

 

“If dicamba is the only weed control used, its lifespan will be greatly curtailed. It all depends on how it is used.

 

It should be used within an integrated system of weed control,” he said. “Keep the fields free of weeds to maximize your yield and use an integrated system that considers row spacing and plant canopy, plant population, good agronomic practices and timing based on the biology of the plants.”

 

In addition, farmers should not cut the rates of application, which will result in a faster evolution of resistant weeds. Walking the fields and taking a hoe to weeds can be an effective technique. “I’ve never seen resistance to a hoe.”

 

The future of dicamba is up to farmers, Hager said. Using the chemical incorrectly can result in dicamba-resistant weeds and further restrictions.

 

“We’d better do it right. Once a plant is resistant to herbicides, that resistance doesn’t go away. We have a weed population that is resistant to herbicides in five classes in Illinois. We can’t assume we won’t find six or seven,” he said. “Fields are biological systems that are dynamic and changing.”

 

“The important thing is how applications are made. If they result in off-target movement, there will be increased scrutiny and further restrictions on the technology.”

 

Hager said there is a difference between a precaution and a restriction. On the label those restrictions are spelled out, and if they are not followed, a farmer can be criminally charged.

 

Dicamba, having been approved for use on soybeans, will be used later in the season this year and so the warmer temperatures, varying wind speeds and volatility mean those using the herbicide need to show extra caution, Hager said. ICIA offers soybean seed tests Meanwhile, seed dealers are anticipating an interest in dicamba-tolerant soybeans.

 

Because of this, the Indiana Crop Improvement Assoc. (ICIA) recently announced it has developed a test for the effectiveness of the seeds.

 

“We’ve gotten a lot of calls from the East Coast because they can’t find a lab that will run tests on dicamba resistance,” said Jeanne Storey, ICIA marketing director. “They are excited about this new product.”

 

ICIA Herbicide Department Head Justin Milcarek said, “Being a testing leader on the newest seed industry trait offerings is our commitment to our customer-focused mission.”

 

ICIA is an independent nonprofit, non-governmental organization that tests for ag quality assurance on new genetics and molecular technology, such as germination rates, native seed, non-GMO and GMO traits.

 

To see a complete list of testing services, visit www.indianacrop.org or call 866-899-2518.