Suppose you’re preparing to spray dicamba herbicide over dicamba-tolerant soybeans. There are woods along one side of the field. The label website says you must leave a buffer next to areas of “desirable vegetation.” However, you own the woods, so there won’t be risk of damage to a neighbor’s property. You decide not to leave a buffer.

Did you make the right call?

“No. You must leave a buffer,” says Scott Gabbard, Purdue University Extension ag educator in Shelby County, Ind. “It doesn’t matter if you own the woods. It’s an area where off-target movement could damage desirable vegetation. This comes from the negotiated agreement between EPA and manufacturers. The same also applies to grassy ditches between fields and roads.”

Several of these “tough call” situations could arise while spraying dicamba this season. Labels are complex. Applying properly without violating the label is like “threading a needle,” Gabbard says.

Other tough calls
Here are more examples of tricky situations, based on Gabbard’s presentation at a required dicamba training session in Johnson County. Anyone who intends to apply new dicamba products must attend training. Gabbard’s explanations are backed up by the Office of Indiana State Chemist.

Rain in the forecast. New labels say you can’t spray if there’s a 51% chance or greater of rain within 24 hours. “What if there’s a 30% chance and I spray, but it rains within the 24-hour window?” one farmer asked. “Am I in violation?”

No, Gabbard said. “It rains in Indiana, and sometimes when there’s a 30% chance, you may get the shower.

“However, I highly recommend you use the National Weather Service as your source of forecast. Record and keep a copy of the forecast to prove that when you made the decision, there was only a 30% chance of rain,” he added.

CRP land located next door. You don’t have to leave a buffer if you’re spraying a new dicamba product next to Conservation Reserve Program land, Gabbard said. It’s considered land that’s not currently used in ag production.

Buffer on more than one side. “If there are non-dicamba-tolerant soybeans on two sides and the wind is blowing at an angle, does that mean I must leave a buffer on both sides?” another farmer asked.

There are situations where you will need buffers on two sides, not just one, Gabbard confirmed. For example, if the wind direction is at a 45-degree angle, you would need a buffer on two downwind sides. OISC recommends recording wind direction in degrees on your official records, not just by direction.

Determining temperature inversion. “Do I need an air balloon to determine if there’s a temperature inversion?” one farmer quipped. While that may seem far-fetched, using a smoke bomb safely to see where smoke goes might be realistic, Gabbard said. If it goes sideways instead of straight up, there may be a temperature inversion underway.

“If you live close enough to a factory or utility to see smoke from a smokestack, if it’s going sideways and not up, check for a temperature inversion,” Gabbard recommended.

For more tips and information gleaned from this training session, read Part 1 and Part 2 of this three-part series.