Iowa weed scientist says damage from dicamba is most extensive he's ever seen

Iowa State University Extension weed scientist Bob Hartzler says dicamba injury this summer is the most extensive he's ever seen.

Hartzler says reports from agronomists across the state indicate nearly all non-dicamba-tolerant soybeans are showing symptoms characteristic of dicamba.

"And it's from fence-row to fence-row in those fields," Hartzler says. "So you can't see where the source came from as the injury dissipates as you move across the field-and that's the type of injury we've never seen before."

Hartzler thinks several factors contributed to the increase in dicamba damage, including confusion over the Ninth Circuit court decision, this summer's environmental conditions, and increased dicamba use on corn.

"The two big things I think happened is that because we got the corn and beans planted so quickly, that both corn and soybean fields were being sprayed with dicamba at the same time. That normally doesn't happen-and so, collectively, we had more dicamba being applied in a very narrow timeframe than we've ever seen in the past."

Hartzler says it still hard to say if yields in injured fields will be impacted.

"In a lot of fields, probably the majority of the fields, the yield is not going to be impacted," he says. "But, in my mind, that's still not a reason to say, 'this is okay.'"

Hartzler says it's hard to predict what will happen with re-registration of the dicamba products later this year. But he says new formulations of dicamba with lower volatility than current products are being evaluated and are projected to be in the marketplace in the future, pending regulatory approvals.

"Those need to be carefully evaluated and see if they really do solve this problem with volatility-and if they are, then let's get them on the market and replace what we're doing there."

Hartzler says significant reductions in volatility and better drift management practices could greatly reduce risks associated with dicamba. And he says the new formulations should also be mandated for use on corn.