The damage in northeast Arkansas and across the Midwest — sickly soybeans, trees and other crops — has become emblematic of a deepening crisis in American agriculture, reports the Washington Post. Farmers are locked in an arms race between ever-stronger weeds and ever-stronger weed killers.
Manufactured by Monsanto and German chemical company BASF, dicamba was supposed guarantee weed control in soybeans and cotton. The herbicide — used in combination with a genetically modified dicamba-resistant soybean — promises better control of unwanted plants such as pigweed, which has become resistant to common weed killers.
The problem, farmers and weed scientists say, is that dicamba has drifted from the fields where it was sprayed, damaging millions of acres of unprotected soybeans and other crops in what some are calling a man-made disaster. Critics say that the herbicide was approved by federal officials without enough data, particularly on the critical question of whether it could drift off target.
The backlash against dicamba has spurred lawsuits, state and federal investigations, and one argument that ended in a farmer’s shooting death and related murder charges.
“This should be a wake-up call,” said David Mortensen, a weed scientist at Pennsylvania State University.
According to a 2004 assessment, dicamba is 75 to 400 times more dangerous to off-target plants than the common weed killer glyphosate, even at very low doses.
Kevin Bradley, a University of Missouri researcher, estimates that more than 3.1 million acres of soybeans have been damaged by dicamba in at least 16 states, including major producers such as Iowa, Illinois and Minnesota.
“It’s really hard to get a handle on how widespread the damage is,” said Bob Hartzler, a professor of agronomy at Iowa State University. “But I’ve come to the conclusion that [dicamba] is not manageable.”
During a July 29 call with EPA officials, a dozen state weed scientists expressed unanimous concern that dicamba is more volatile than manufacturers have indicated, according to several scientists on the call. Field tests by researchers at the Universities of Missouri, Tennessee and Arkansas have since found that the new dicamba herbicides can volatilize and float to other fields as long as 72 hours after application.
Although pesticide-makers often supply new products to university researchers to conduct field tests in varied environments, Monsanto acknowledged it did not allow that testing on its commercialized dicamba because it did not want to delay registration.