The Office of the Indiana State Chemist will assess how state-specific restrictions on dicamba could affect the use of the herbicide in the state.

The OISC’s Pesticide Review Board voted to review the ramifications of declaring dicamba a “highly volatile herbicide,” a move that could allow the state to better regulate the use of the controversial chemical in Indiana. Dicamba has been associated with crop destruction caused by drifting of the chemical from the original application site.

The decision comes after the U.S. Environmental Protection Agency approved five-year registrations of Monsanto Co./Bayer AG’s XtendiMax with VaporGrip Technology and BASF’s Engenia Herbicide and extended the registration for Syngenta’s Tavium Plus VaporGrip for use on dicamba-tolerant cotton and soybeans until 2025.

The registrations come with new federal requirements for pesticide applicators, some of which the OISC says may not be the best fit for Indiana and may require state-specific restrictions.

Declaring dicamba a “highly volatile herbicide” would give the state chemist authority to set state restrictions on the chemical that would differ from the federal registration.

The registration allows the sale and use of the products as long as several control measures are followed, including the mandatory addition of a pH-buffering agent to tanks when the products are used, mandatory downwind buffer areas where some listed species are located, the simplification of labels and use directions and strict application deadlines for soybeans and cotton.

The EPA set a universal June 30 cutoff date for dicamba application on soybeans and July 30 for cotton, deadlines that run counter to the OISC’s need determinations for Indiana.

“Realistically, if we were trying to normalize dicamba applications and the resulting off target movement incidents with every other active ingredient we know, we’d probably pick June 5 or June 10. But dicamba today is not like everything else because it will control some of those weeds that the other herbicides won’t. So that’s part of the calculation, but our opinion is that June 20 was helpful as a cutoff date and we would recommend it again,” said OISC Pesticide Program administrator David Scott during a meeting of the Pesticide Review Board.

The OISC, which regulates agricultural laws involving pesticides, fertilizers, animal feed and seeds in the state, mostly depends on federal mandates to regulate dicamba and other pesticides, but within the last year and a half the OISC began to set its own restrictions to address dicamba issues.

When dicamba was introduced for soybeans, Indiana had no specific state restrictions or requirements until 2018, when the state mandated training for applicators. That mandate was removed in 2019.

To address a growing number of drift complaints in the state, the OISC in late 2019 set an application deadline of June 20 for the 2020 growing season.

The new deadline of June 30 could negatively affect farmers in the state.

“Without a doubt the benefit to the use of these products is that there are weeds you can’t control without them. We think the cost starts getting a little high, unacceptably high, after June 20,” said Scott.

The OISC investigates complaints about drift and other situations involving pesticides. Since 2017, dicamba products have been the subject of most of the OISC’s drift investigations.

The OISC’s June 20 deadline reduced the number of dicamba complaints by more than 55% in a single year.

The OISC found that the June 20 deadline for dicamba application reduced 66% of the year’s dicamba complaints. A June 30 cutoff date would only reduce 52% of incidents.

Scott said the EPA made its registration decision without input from the state of Indiana, despite states offering to comment on label language and restrictions.

“One solution does not fit every geographic location, and I think this is an example of that. We suggested options of how they might address that. They elected to not take our advice, and they picked a date and made it universal,” he said.

The OISC will review what could happen if dicamba is declared a “highly volatile herbicide.” The findings will be presented at the next Pesticide Review Board meeting in mid-February.