With growers reporting dicamba damage to 3.1 million acres of soybeans, the harvest-time question for farmers is how much their yields will suffer from the weedkiller. University of Tennessee weed specialist Larry Steckel says the earlier that soybeans were hit in their lifecycle, the less likely yields will be reduced.
“There have been a few reports of yield loss in the 5 to 10 percent range for fields that were drifted on when the soybeans were in the early reproductive period in late June or early July,” Steckel wrote on a university blog. “The reported yield loss has been considerably higher for fields drifted on multiple times. These of course are estimates. It is very hard to get a precise figure as often there are no areas in these fields that did not suffer dicamba injury to check against.”
In a few cases, soybeans are not maturing properly or noticeably lack pods on the top half of the plant. “This has typically been on later-planted soybeans that were apparently exposed to dicamba at a very susceptible soybean growth stage/stages,” wrote Steckel. He said overall yields in Tennessee “will be very good again this year. We have been very fortunate with the weather helping mitigate all the dicamba drift damage on the soybeans in 2016 and 2017.”
Health Canada will not change its guidelines for dicamba although the EPA announced additional restrictions on how and when the herbicide in used on cotton and soybeans, reported Grainews. “There appeared to be a much lower level of damage in Canada, where there was a campaign to encourage farmers to only use the system with pre-plant and pre-emergent timing and where there are fewer herbicide-resistant weed challenges.” The Canadian rules already contain some of the provisions adopted by EPA, such as ban on spraying when winds exceed 10 mph. Like EPA, Canada sets specific instructions on cleaning sprayer tanks to prevent contamination.