The EPA is reviewing dicamba use to see if the herbicide can be used safely to avoid damaging non-target crops.
The agency reported Tuesday about the number of instances where dicamba drifted onto plants other than those targeted by the widely used herbicide. The report includes a 73-page memo authored by agency biologists, advisors, economists, and agronomists.
An update about the report on the EPA website also says the agency is committed to a public hearing process before making regulatory changes. Without a voluntary request to cancel the registration of dicamba, “it is unlikely that this process could occur and be fully implemented before the 2022 growing season.”
Dicamba-resistant crops account for about 75% of cotton acres and 66% of soybean acres planted nationwide.
The agency received 3,461 reports of off-target dicamba damage in 2021. The herbicide impacted more than 1 million acres of non-dicamba-tolerant soybeans alone.
Agency scientists believe those figures are underreported.
A survey found that only 6% of growers reported every single event.
“The most common reasons for not reporting included: concerned with creating bad neighbor relations, saw no benefit in reporting, consequences to the offender were not meaningful, and unable to identify the source of the drift,” the report reads.
Arkansas, Illinois, Indiana, Iowa, Kansas, Minnesota, Missouri, Nebraska and South Dakota each reported more than 100 incidents of off-target dicamba damage. Kentucky, North Dakota, Ohio, Tennessee, and Wisconsin reported between 10 and 100 incidents. Delaware, Florida, Georgia, Louisiana, Maryland, Michigan, Mississippi, New Jersey, New York, the Carolinas, Oklahoma, Pennsylvania and Virginia each reported less than ten incidents.
While soybeans that can’t withstand dicamba were the most common victims, other incidents involved tree or shrub nurseries, potatoes, sugarbeets, sweet potatoes, pepper, pumpkin, squash and tomatoes.
Some crops are far more sensitive to dicamba than others. For example, snap beans are 1.5-3.2 times more sensitive than soybeans.
The off-target effects aren’t simply a matter of wind, state researchers found.
“The majority of states reported that while some incidents may be due to spray drift, the majority are likely due to volatility,” the memo reads in part.
The cutoff date for dicamba use is June 30 for soybean, in order to prevent high temperatures from evaporating dicamba and allowing it to spread further.
In some cases, dicamba damage was observed more than a mile away from the nearest application. In one instance in Arkansas, dicamba damage was reported more than 20 miles away from the nearest application.
Beyond crops, damage was observed outside of croplands. Researchers in Arkansas — which also reported the largest acreage of possible dicamba exposure — recorded more than 200 instances of non-crop species damaged by dicamba, including sycamore trees in the Dale Bumpers White River National Wildlife Refuge. Other impacted areas included university research farms, cemeteries, churchyards, state wildlife properties and natural areas, city parks and national wildlife refuges.
Regulators in the various states disagree on how to address the problem. Some regulators in states with low incidents want to preserve and increase the use of over-the-top dicamba. Other regulators “see this technology causing widespread landscape-level damage ,” according to the memo.
The review was reported as researchers in Tennessee, Illinois, and Indiana each reported dicamba-resistant strains of waterhemp, and as dicamba resistance is showing up in Palmer’s amaranth. Both weeds are species of pigweed.
A Ninth Circuit Court of Appeals order vacated registrations for three dicamba products in June 2020. The agency subsequently reinstated the registrations of several products and approved two new products for use on dicamba tolerant cotton and soybeans.
Dicamba is one herbicide used in no-till and other conservation practices.