Farmers may have had dicamba in their weed arsenal for more than 50 years, but the agronomic tool took a divisive turn in 2017.
Unprecedented complaints of injury to sensitive crops were recorded across the U.S. during the first full year of the Roundup Ready Xtend Crop System, despite new, lower-volatility dicamba formulations and education campaigns on how to reduce spray drift.
In October, a survey of Extension weed specialists estimated off-site movement of dicamba had injured 3.6 million acres of soybeans. Officially, there were 2,708 dicamba-related injury cases under investigation by various state departments of agriculture. Included in those cases were complaints that dicamba injured vegetable and fruit crops, trees and homeowner landscapes.
Many had hoped the long list of complex restrictions the Environmental Protection Agency (EPA) placed on the Engenia, FeXapan and XtendiMax labels would help applicators keep the herbicide on-target. At the same time, the weed science community voiced stern warnings that those labels did nothing to address the inherently volatile nature of dicamba.
As complaints of cupped and puckered leaves characteristic of dicamba injury started to mount in June and July, states such as Arkansas, Missouri and Tennessee, took action to temporarily restrict or ban applications.
Farmer-to-farmer accusations flew, too. Many of those seeking to curb herbicide-resistant weeds were thrilled with the new control measures, but less happy were neighbors who suffered chemical trespass. Fortunately, good growing conditions helped reduce some dicamba-injury yield losses in 2017. “Drought conditions wouldn’t have been as kind,” noted University of Tennessee weed scientist Larry Steckel.
The fact that soybean yields rebounded from damage did nothing to reduce the issue of chemical trespass. EPA responded by classifying the three herbicides as restricted use pesticides and tightening spray requirements further for 2018. Slower sprayer speeds, higher water volume requirements, restricted spray hours, nozzle limitations, temperature maximums, lower wind speed limitations and mandated applicator training were put in place.
Weed scientists again warned that the new EPA practices designed to reduce misapplication do not address volatility concerns. Meanwhile, Monsanto and BASF have denied product volatility claims and pinned most of the 2017 injury on a mixed bag of applicator error, tank contamination, errant tank mix partners, use of older formulations — factors the companies claim can be addressed with more education.
Who is liable for the loss associated with injury is also adding to the drama — both from the farmer and retailer applicator perspective. Recent issues with dicamba spray drift have highlighted the need for producers to understand third-party liability associated with all herbicide applications, said University of Missouri Extension economist Ray Massey.
Product labels for 2018 labels also are so restrictive that the window for making legal applications could be very narrow. A Purdue University report during the December North Central Weed Science Society meeting calculated an applicator had 184 hours to spray XtendiMax or FeXapan during June 2017. Using the new 2018 label restrictions, and identical weather patterns, applicators will have only 44 hours to spray next June.
Some individual states were also taking additional measures beyond federal labels as farmers were headed into seed selection season. In Arkansas, where the dialogue has been most heated, Monsanto and some farmers have been legally pushing for broader market access to dicamba. Legislators agreed in December and kicked a proposal to ban most in-season use back to the Arkansas State Plant Board for further consideration.
With one spray season left on a conditional EPA label, several Midwest weed scientists are now urging farmers to consider applying dicamba only preplant, preemergence or very early postemergence. “Over 90% of the offsite movement complaints resulted from postemergence applications,” stated a November bulletin issued from the Ohio State, Purdue University and the University of Illinois. http://bulletin.ipm.illinois.edu/wp-content/uploads/2017/11/Dicamba-Precautions.pdf
Meanwhile Monsanto projects the Xtend acreage will grow to 40 million acres in 2018. Article via Pamela Smith at DTN Progressive Farmer.