While problems experienced with off-target movement and injury in states like Missouri, Arkansas and Tennessee have been well covered in the media, an Iowa State weed specialist says that doesn’t mean all is well in his state.
Bob Hartzler says that while he doesn’t know the percentage of Xtend soybean fields experiencing problems with off-target movement of dicamba, “in my mind the number is too high.”
Hartzler says the majority of off-target injury has been to soybeans in the vicinity of Xtend soybean fields. This is due to soybean responding to much lower concentrations of dicamba than most other plants.
“I recently visited a site where soybeans in at least three fields, managed by two different farmers, showed dicamba symptoms. The only dicamba used in the area was applied to an Xtend field upwind of the injured fields,” Hartzler wrote. “I am not aware of any fields where the damage would be described as severe. However, in most fields, I don't think it’s possible to know whether the injury will limit yields. In many cases the entire field shows damage, making it difficult to document yield effects.”
Meanwhile, Monsanto isn’t backing down from the position that its herbicide — the Roundup Ready Xtend dicamba-tolerant system for soybeans and cotton — isn’t inherently flawed.
Robb Fraley, Monsanto Executive Vice President and Chief Technology Officer, told media on a conference call that on the vast majority of farms he has visited over the past 3 weeks where drift has been a problem, it was likely due to “not having adequate buffer separation differences and spraying in wind conditions.”
Fraley pointed out several instances in Arkansas and Missouri where he saw cupping that could not have been from drift because of the pattern of impact.
“Most agronomists will tell you that uniform, corner-to-corner leaf cupping across an entire field is not consistent with drift; it’s symptomatic of another problem,” he says. “Are those uniform problems with cupping because of a problem with a contaminated sprayer unit? Are they due to improper spraying of older dicamba formulations that have a propensity to vaporize?”
Not only is user error assumed to be at the root of snowballing drift cases this season, according to Monsanto officials, but Fraley also speculated illegal use of older, generic dicamba formulations could approach 25% of applications.
Back in Iowa, Hartzler says the Iowa Department of Agriculture and Land Stewardship (IDALS) received eight drift/off-target herbicide complaints attributed to dicamba. The relatively low number of 'official' complaints could be taken as a good sign, he says, but most farmers/applicators try to solve the problem without involving the state.
The EPA requires companies with dicamba formulations registered for use on Xtend soybeans (BASF, DuPont and Monsanto) to report all cases of non-performance and off-target injury. When these data are available, they will provide a better estimate of the frequency of problems than the IDALS numbers. Hartzler adds he doesn’t know how frequently the company is notified in these situations, especially when the injury level is low.
“While growing pains are often experienced when new products are introduced, the frequency and size of area affected by off-target dicamba movement is much greater than with other new products,” Hartzler says. “Many other plants on the landscape are sensitive to dicamba, including fruits, vegetables, trees and other ornamentals.
“My concern is that as the acres of Xtend soybean treated with dicamba increases, the injury will become more widespread and not be limited to soybeans.”
