Steven Knezevic

Dr. Steven Knezevic talks during a UNL Extension field day in Concord, Neb., July 24.

Dicamba products, regardless of brand, are all equally harming soybeans and other crops, according to Dr. Steven Knezevic.

Knezevic, who is a professor with the University of Nebraska-Lincoln (UNL), studied herbicides and other chemicals in Nebraska for more 20 years when he was was tasked with finding out the volatility in dicamba products. The project came up two years ago when the first major round of dicamba damage occurred throughout the U.S. He was on hand to discuss his findings at the UNL Science and Ag Family Field Day July 24 in Concord, Nebraska.

“There has been no other time where there has been a greater division in opinions on dicamba between chemical companies and university educators,” he said.

Over the last two years, Knezevic his fellow educators have been trying to explain that dicamba is not the silver bullet that everyone wants it to be for weed control. He said he’s gotten pushback from chemical companies. And now, he said, many educators don’t even agree on how valuable dicamba really is to the market.

His tests pitted several of the top dicamba products – including Xtendimax and Engenia – and found that all products equally treated weeds and equally damaged soybeans that weren’t genetically modified to tolerate the chemical.

His test looked at how 1/100th of the label rate of dicamba products would affect non-tolerant soybeans, grapes and tomatoes.

Knezevic found that each plot’s growth period and yield were damaged by dicamba and each product damaged them relatively the same with only a one- or two-bushel yield difference between products.

With these results, Knezevic found something that he had already concluded many years ago – dicamba is not the answer.

When glyphosate came out and was deemed the silver bullet, he warned people not to overuse the product, he said. Now that weeds are resistant to glyphosate, dicamba has become big again and he worries the same will happen. By his calculations, seven weeds are resistant to dicamba products so far.

Even more concerning, many people don’t understand how much more dangerous dicamba is than glyphosate to neighboring fields. He stressed that producers, should they use the product, read the label and make sure everything is absolutely correct.

“With glyphosate-based products, I don’t think many people knew that the label existed,” he said.

Dicamba fully destroyed the grapes and tomatoes in Knezevic’s test.

There are studies underway to test how much dicamba drifts, but Knezevic said he believes even 1/500th of the label rate is enough to damage crops. Because of this, Knezevic said he was upset to learn that chemical companies are trying to say that some dicamba drift could actually be helpful.

“It’s a myth,” he stated plainly.

A colleague from another university did a study and found that there is no evidence dicamba would help non-tolerant crops, it could only hurt.

Knezevic said he doesn’t expect there to be a silver bullet to weed control, rather it is about managing risk with glyphosate and dicamba alike.

The only hope he shared came from his optimism for the new Enlist product, 2,4-D. With his limited tests, Knezevic found Enlist is a safer version of dicamba for the open market.

Correction: In a previous version, it was implied that Liberty was an dicamba product. It was meant to say Xtendimax and Engenia and has been fixed. 

Reach Reporter Jager Robinson at 605-335-7300, email or follow on Twitter @Jager_Robinson.


Jager is a repoter for Tri-State Neighbor, covering South Dakota, southwestern Minnsota, northwestern Iowa and northeastern Nebraska.