Editor's Note: DTN is running a series of stories called Dicamba Rules Update, which explores the new dicamba labels. In the third story of the series, DTN explores the new buffer requirements applicators will have to navigate in 2021.
ROCKVILLE, Md. (DTN) -- Buffer requirements for dicamba applications are both larger and more complex this year.
When EPA released its new five-year registrations for XtendiMax, Engenia and Tavium in the fall of 2020, the agency expanded the size of downwind buffer requirements and buffers for counties with endangered species. Weed control in these areas will need attention, weed scientists told DTN.
EPA has also updated its list of counties with endangered species, so applicators will need to check carefully for new additions or changes in their state. The agency also offered growers a chance to shrink these buffers -- but only if they use very specific hooded sprayer equipment, and only for soybean fields, not cotton.
The new labels now require a downwind buffer of 240 feet between the last treated row of a field and the nearest downwind field edge. Remember that NO dicamba applications are permitted if the wind is blowing -- at any speed -- toward a sensitive crop or plant.
The labels also list a second buffer requirement -- a 57-foot omnidirectional buffer as well as a 310-foot downwind buffer to protect endangered species. These buffers are only required for fields in counties that have been listed on EPA's Bulletins Live! Two website, because they house federally recognized endangered species.
Do not assume that if a county didn't surface on this website last year, it won't be on it this year.
The EPA has adjusted its list of counties with endangered species in several states, and dicamba applicators are required to document that they checked this website before spraying.
For example, Indiana applicators now have six counties listed with endangered species, up from just two last year, noted Purdue University weed scientist Bill Johnson. In Illinois, counties with endangered species shrank from 27 in 2019 to just 18 this year -- but five of them are newly listed, University of Illinois weed scientist Aaron Hager cautioned in this blog post: https://farmdoc.illinois.edu/….
Applicators can find the Bulletins Live! Two website here: https://www.epa.gov/….
WHAT COUNTS AS A BUFFER?
For the downwind buffers, applicators can use the following areas as part of their 240-foot buffer:
-- Roads, paved or gravel surfaces, mowed grassy areas, and areas of bare ground from recent plowing or grading that are contiguous with (touching) the treated field.
-- Certain crops that are proven to tolerate post-emergent dicamba exposure, such as corn, dicamba-tolerant cotton, dicamba-tolerant soybeans, sorghum, proso millet, small grains and sugarcane.
-- Agricultural fields that have been prepared for planting.
-- Areas covered by the footprint of a building, silo, or other man-made structure with walls and/or a roof.
However, for counties with listed endangered species, this changes. For those required 57-foot and 310-foot buffers, applicators must follow the buffer options listed on EPA's Bulletin Live! Two website, which are not as numerous:
-- Roads, paved or gravel surfaces, mowed grassy areas adjacent to field, and areas of bare ground from recent plowing or grading that are contiguous with the treated field.
-- Planted agricultural fields of dicamba-tolerant cotton or soybeans.
-- Areas covered by the footprint of a building, silo, or other man-made structure with walls and or roof.
Note that, for endangered species buffers, unplanted agricultural fields and dicamba-friendly crops like corn, sorghum, millet, small grains or sugarcane CANNOT be used as part of the buffer. Applicators can only use planted dicamba-tolerant soybeans or cotton fields.
HOODED SPRAYER OPTION
This year, the new dicamba labels offer applicators the option of reducing the downwind buffer to 110 feet and the endangered species buffer to 240 feet if they use a hooded sprayer.
Because the EPA only reviewed a limited dataset on using hooded sprayers to reduce dicamba drift, this label option is very narrow; it is ONLY available for Xtend soybean fields, not cotton, and applicators must pick from a short list of qualified hooded sprayers.
You can see the list of hooded sprayer options here:
-- XtendiMax: https://www.xtendimaxapplicationrequirements.com/….
-- Engenia: https://www.engeniaherbicide.com/….
-- Tavium: https://www.syngenta-us.com/….
See a DTN story on the use of hooded sprayers here: https://www.dtnpf.com/….
BE READY TO CONTROL WEEDS IN BUFFERS
For many growers, particularly in counties with endangered species, growers may have to leave substantial portions of their field unsprayed due to these new buffer requirements. Growers will need a plan for weed control on those field edges, Johnson advised.
That could mean spring tillage to control early flushes, or even in-row cultivators if row spacing permits, he said. Narrow row spacing can help smother out weeds, as can high biomass cover crops planted in the fall, such as cereal rye. But most growers will probably have to finesse their herbicide program to keep those buffers clean.
"Use a full rate of a broad-spectrum residual herbicide that has two to three sites of action, particularly with activity on waterhemp, marestail, lambsquarter and giant ragweed," Johnson said. "After soybeans and weeds emerge two to three weeks after planting, scout and use post-emergent herbicide treatments on small weeds, 4 inches or less, most likely with Roundup or Liberty plus other herbicides depending on what weeds are present."
For a handy chart that breaks down the changes in the new dicamba labels, see this DTN story here: https://www.dtnpf.com/….
If you missed the other Dicamba Rules Update series stories, go here:
Dicamba Rules Update - 1
Dicamba Rules Update - 2
Emily Unglesbee can be reached at Emily.firstname.lastname@example.org
Follow her on Twitter @Emily_Unglesbee
(c) Copyright 2021 DTN, LLC. All rights reserved.