GRAND FORKS, N.D. - U.S. soybean growers and the people who work with them are "on probation" with their use of the herbicide dicamba, a North Dakota State University extension weed specialist said.

"The bottom line is, we're on probation. We have to demonstrate to the (Environmental Protection) Agency that we can successfully apply these products," Tom Peters said.

Peters spoke Feb. 23 at the International Crop Expo in Grand Forks.

Dicamba has been used for many years in wheat and corn. It helps to control weeds by causing them to grow abnormally and often to die. More recently, dicamba-tolerant soybeans were developed because of growing weed resistance to glyphosate, a widely used herbicide. Monsanto, BASF and duPont are all selling versions of it.

But dicamba also can hurt some other crops, including non-dicamba-tolerant soybeans, sugar beets and potatoes unless label restrictions are followed very carefully. Spray drift to surrounding fields is a particular concern.

Late last year, the EPA approved short-term registration for a new dicamba formulation that can be used on dicamba-tolerant soybeans. The registration - effective in 38 states, including North Dakota, South Dakota and Minnesota - will expire on Nov. 9, 2018, two years after it was first approved, if EPA decides there have been too many problems with its use.

Under the Obama administration, EPA was looking for "more balance between weed control efficacy and balance with the environment - in this case, protecting endangered species. In my mind, that's what this is all about," Peters said.

Dicamba will be especially tricky to use properly in soybeans, Peters said.

Area farmers have been using dicamba since the 1960s in wheat and corn fields. But in 2017, for the first time, dicamba will be used on resistant soybeans later in the growing season, and in larger dosages, than in the previous wheat and corn applications, he said.

Successful use of dicamba will require following the pesticide label, learning best management practices and developing awareness for sensitive crops, he said.

But reading the label directions alone won't suffice. Proper use of dicamba also requires careful and regular study of websites that offer more and updated information of the product, Peters said.

"You have to use both (label and website.) If you don't want to do the reading and the homework, maybe you shouldn't use this technology, because there's a lot of rules associated with it," Peters said.

His overall assessment:

"We have a really useful tool, but we'll have to use it carefully and correctly to be successful in 2017," Peters said.