By Christina Rice

Kevin Bradley, a weed scientist from the University of Missouri Extension, spoke to agriculturists on March 2 in the Nodaway County administration building about the extensive damage to Missouri crops in 2016 caused by farmers and spray applicators illegally spraying dicamba formulations on soybeans.

Kevin Bradley, a weed scientist from the University of Missouri Extension, addressed citizens of Nodaway County on the proper use of dicamba herbicide.

Several weeds including water hemp and pig weed are becoming resistant to current herbicides on the market. Companies created new genetically-engineered seeds that would withstand harsher herbicides in order to keep the weeds under control.

In 2015, Monsanto’s Roundup Ready Xtend soybeans were released on the market. However, the Environmental Protection Agency (EPA) had not yet approved the herbicide dicamba that was intended for use on the Xtend crops leaving farmers no legal herbicide they could use on the crops they had planted.

Some farmers in the state decided to spray the crops with dicamba anyway even though it was not legally approved for use.


The drift killed more than 45,000 acres of reported non-Xtend crops, several miles away from the original sprayed source. Crops such as other types of soybeans, tomatoes, peaches, raspberries and all organic crops were highly affected.

Other genetically-altered crops that are resistant to the dicamba herbicide include corn and cotton.

There are currently some dicamba formulas that can be legally sprayed on corn. These formulas have not resulted in the magnitude of cross-field contamination that resulted from the sprayed beans. Bradley and other researchers conducted several experiments to determine what caused the excessive drift on bean cropland.

Dicamba is more potent than any other herbicide on the market, according to Bradley. Their studies showed that 1/20,000 of the approved amount is enough to negatively affect non-resistant crops. Those impacted after the flowering stage will not recover and germination for the following year will be reduced by up to 50 percent.

Some farmers also sprayed twice as much per acre than the EPA approved for 2017’s label, among other inaccurate application factors.

The team discovered that temperature inversions played a role in the major drift issues. The herbicide was sprayed and trapped in the cool air layer that stays under the warm air layer. As the wind moved horizontally across the land, it carried the trapped herbicide miles away, damaging crops.

When corn is sprayed with formulations containing dicamba, it is sprayed earlier in the season before other crops are flowering. Soybeans are sprayed later in the summer months when other crops are in bloom, causing the researchers to suspect timing plays a role in crop damage.

Legal applications

In 2017, farmers may legally spray XtendiMax with VaporGrip, Engenia and FeXapan plus VaporGrip as long as they follow the federal and supplemental label regulations.

Some of the regulations are:

•Applicators must have checked company websites for changes seven days prior to spraying.

•Spray can not stay in the boom overnight.

•There must be a 110- to 220-foot buffer between fields that are being sprayed and other fields.

•Only certain nozzles are allowed.

•Wind must be between three and 10 mph and up to 15 mph in certain circumstances.

•Fields can not be sprayed if rain is predicted within 24 hours.

•Spray droplets must be the approved size.

•Boom height must be 24 inches above ground, making this difficult in terraced areas.

•AMS can not be added to the spray tank.

•Tanks must be washed with water, ammonia and water, in that order.

Read the label

Wayne Flanary, University of Missouri Extension regional agronomist, stressed that the label states that the responsibility falls on the applicator. He also wanted people to understand that if they only follow the federal label and not the supplemental label, they will be out of compliance. The labels state that the supplemental label trumps the federal label on any inconsistencies.

Bradley stated that dicamba still may not be the best choice for weed control. It’s good for killing water hemp that is less than four inches tall and will not kill the weed if it is above 12 inches tall. He stated that by the time the farmer notices the weed and waits for the right conditions to spray, the weeds could have grown too tall making the herbicide ineffective.