Editor's Note: Dicamba herbicide use on soybeans and cotton is expected to expand dramatically in 2017. Stewardship will be critical to avoid drift and other movement onto sensitive crops and plants. This Dicamba Decisions series examines important application issues and the tough new federal label requirements of the new dicamba herbicides.
ROCKVILLE, Md. (DTN) -- Applicators face complex and sometimes ambiguous buffer requirements for the newly labeled dicamba herbicides this year.
The labels for Monsanto's XtendiMax, BASF's Engenia and DuPont Pioneer's FeXapan put all the responsibility for following buffer requirements and avoiding off-target drift on the applicator. That is a heavy burden for commercial applicators, in particular, who juggle multiple jobs in a day and spray fields they may not know.
That means conversations about what is surrounding a field of Xtend soybeans and cotton need to happen now, and they need to involve the grower and retailer as well as the applicator, said Purdue University weed scientist Bryan Young.
"Applicators have got to do their homework before they get to the field," he said. "The requirements on this label that are up to applicator -- knowing the proximity of sensitive crops, susceptible crops and endangered species -- they can't do that from the cab." Growers will also need to pick the fields where they plant Xtend cotton or soybeans with great care, he added.
Growers and applicators should become comfortable with three key phrases in the new labels: "Sensitive areas," which require a downwind buffer at all times and "non-target susceptible crops" and "specialty crops," which vary in spray restrictions among companies.
When spraying the new dicamba herbicides, applicators must leave a 110-foot downwind buffer (or 220 feet, if using the higher rate of XtendiMax and FeXapan) between the edge of the field and neighboring "sensitive areas."
The EPA declined to define "sensitive areas" on the herbicide labels, which means companies, scientists and applicators have been forced to come up with their own interpretations. In its 24(c) labeling for Engenia, North Carolina made a point to define "sensitive areas" as "residential areas, bodies of water, known habitat for threatened and endangered species or dicamba-sensitive crop plants," a broad definition that most experts accept.
The buffer requirement for these areas aims to minimize dicamba exposure to non-target organisms, particularly threatened and endangered species, Monsanto Crop Protection Systems Lead Ty Witten noted. Chad Asmus, BASF technical marketing manager, recommends growers and applicators reach out to their local and state Extension offices or agriculture departments for clarification on which threatened or endangered species might be in their area.
A number of things can count as part of that buffer, including paved or gravel roads, unplanted agricultural fields, buildings or certain crops that tolerate dicamba, such as Xtend soybeans, Xtend cotton, corn, sorghum, millet, small grains and sugarcane.
The label includes stricter and more complex restrictions to protect "non-target susceptible crops" or "desirable plants" -- that is, crops and plants that could be killed or rendered less commercially valuable by dicamba drift, Young noted.
In this section, the labels specifically forbid spraying when the wind is blowing -- at any speed -- in the direction of "specialty crops." For XtendiMax, this includes non-dicamba-tolerant soybeans. "Soybeans are one of most sensitive species" to dicamba, Witten said. "If that adjacent field is non-Xtend soybeans and the wind is blowing toward it, you should not apply XtendiMax at that time."
For Engenia, however, BASF is not considering non-dicamba-tolerant soybeans to be among the specialty crops, but rather part of the "sensitive areas," Asmus said. That means growers can spray Engenia in fields where the wind is blowing (from zero to 10 mph, provided there is no inversion) toward a non-Xtend soybean field, but only with a 110-foot buffer. For help with the Engenia buffer requirements, see this BASF chart: http://bit.ly/….
Other specialty crops that are specifically identified on the labels are commercially grown tomatoes, fruiting vegetables (EPA Crop Group 8), cucurbits (EPA Crop Group 9) grapes, peas, potatoes, tobacco, flowers, fruit trees and ornamentals. (See the EPA Crop Groups here: http://bit.ly/…).
The labels also include blanket bans on spraying when drift could occur to "food, forage, or other plantings that might be damaged or the crops thereof rendered unfit for sale, use or consumption" or "foliage, green stems, exposed non-woody roots of crops and desirable plants."
How close do these specialty crops and desirable plants need to be to trigger these restrictions? That's not clear from the labels and companies are telling applicators to use their best judgment, Young noted.
"The lack of direction there is concerning," he said. "Personally, I would want to make sure that something very sensitive to dicamba, like tomatoes, is at least a quarter mile away." At least one tomato processor -- Red Gold Inc. -- has released letters asking growers to leave at least a half-mile between their Xtend fields and tomato fields.
Remember to use any available specialty crop registries, such as Field Watch (https://driftwatch.org), and consider contacting local specialty crop commodity groups for more information on crops in your area.
BUFFER WEED CONTROL
Growers have limited options for weed control within downwind buffers. One option is to wait until the wind stops blowing in that direction, and try to make a dicamba pass then, time permitting, Witten said. Otherwise, they will have to use alternative herbicides or target those areas for other weed management strategies, such as hand weeding.
To be safe, growers should be especially diligent with pre-emergence residual herbicides this spring with their Xtend fields, Asmus added.
Young recommends "framing" Xtend fields with the highest labeled rate of a residual herbicide to reduce the chance of weed issues in the field borders later in the season. Planting a cover crop, such as cereal rye, in field borders could also help supplement weed management efforts there, he added.
To add to the complexity of these restrictions, at least one state -- Arkansas -- has passed a rule with more restrictive buffer requirements for applicators spraying dicamba within that state. The rule requires a default 100-foot buffer zone in every direction, as well as a quarter-mile downwind buffer for any "susceptible crops."
The rule applies only to Engenia, as Arkansas has banned the use of DGA-based dicamba herbicides (including XtendiMax and FeXapan) between April 15 and Sept. 15, and Monsanto will not be selling XtendiMax in that state this year. See the Arkansas rule here: http://bit.ly/….
A number of other states are still working on rules regarding the new dicamba herbicides, so all applicators should check with their respective state Plant Board or Extension weed specialists to get state-specific information before spraying.
FIELD SELECTION AND COMMUNICATION
Amid these tough and confusing new buffer restrictions, one clear lesson emerges: Choose your Xtend crop fields carefully, Young said.
"Some fields just aren't going to be good candidates for Xtend crops and dicamba applications," he said.
He recommends Xtend growers have early and ongoing conversations with neighbors to choose fields that are going to be surrounded by other Xtend crops, corn, sorghum or other non-dicamba-sensitive crops.
The labels and herbicide companies have made it clear that the final responsibility for correctly maintaining buffers and avoiding spray drift falls squarely on the shoulders of the applicator. That's a heavy burden -- and one that farmers and retailers should help lighten, Young said.
"You have to have conversations now, because time is short when it comes to spraying," he said. "The applicator needs help getting this information. I'm urging them to work with the retailer who gives them the spray ticket as well as the growers."
Emily Unglesbee can be reached at Emily.firstname.lastname@example.org
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