Minnesota will ban spraying dicamba-based herbicides after June 20, according to the state agriculture department. Dicamba spraying will also not be allowed if temperatures are over 85 degrees, since research has shown that high temps increase the herbicide's volatility.
Arkansas had proposed an April 15 deadline for spraying dicamba, but a legislative panel advised a state plant board to review the proposal in light of scientific-based evidence and other factors. Monsanto has sued the state to prevent the state from implementing the April 15 deadline, saying that it would hurt Arkansas farmers. Missouri, Tennessee and North Dakota have also announced statewide deadlines for spraying dicamba.
Dicamba has been used for more than 50 years, on fields only before crops sprouted. With the recent introduction of soybeans and cotton genetically modified to withstand dicamba, farmers now spray it on sprouting crops. That became a problem because dicamba tends to vaporize into a powder and blow into other farmers' fields, damaging crops that aren't resistant to it.