Dicamba Rule Changes and Recommendations
May 3, 2021
By: Tommy Butts, Tom Barber, and Jason Norsworthy
On May 3rd, 2021, the Arkansas State Plant Board (ASPB) met and voted to alter the 2021 rules for over-the-top use of dicamba in soybean and cotton. In addition to federal label requirements, the specific Arkansas rules (available here: Arkansas Dicamba Emergency Rules) are as follows:
- Cut-off date for over-the-top use of reduced volatility formulations of dicamba for both soybean and cotton is June 30th,
- 1-mile buffer, in all directions, from University and USDA research stations,
- ½ mile buffer, in all directions, from all certified organic crops and commercially grown specialty crops (defined as a minimum of 1,000 plants or the average annual crop sales for the previous 3 years exceeding $25,000),
- ¼ mile buffer, in all directions, from non-dicamba-tolerant crops, and
- Glyphosate is still prohibited from being tank-mixed with dicamba after April 15th.
These changes were passed by the ASPB as an emergency rule, meaning they went into effect immediately following approval by the Arkansas legislature and governor which occurred on Saturday, May 8th.
In addition, make sure to follow all federal label requirements such as using approved nozzles, tank-mix partners, and other application factors (available on product-specific websites), and add the required volatility reduction agent (VRA) in tank-mix (Sentris or Vaporgrip Xtra). Also, if no Arkansas specific buffers apply, the federal label still requires a 240-foot downwind buffer in all application situations. Refer to product specific labels for more information on this buffer requirement.
On May 6th, 2021, the Arkansas Supreme Court ruled the current appointment process for the ASPB was unconstitutional and declared that the 9 individuals not appointed by the governor must be immediately removed from the board. It appears that this ruling does not impact the change in dicamba rules accepted by the ASPB on May 3rd, but will change the process in which ASPB members are selected to board positions moving forward.
As far as our weed control recommendations for dicamba-resistant soybean and cotton, they have remained relatively unchanged.
It is important to start clean and use a robust PRE program with multiple, effective modes-of-action, 2 is always better than 1. Metribuzin should be a base tank-mix partner in soybean PRE programs, and some combination of Brake, Caparol, and Cotoran should be used in cotton PRE programs. Overlap residuals 14 to 21 days following the PRE; make sure to never let pigweed get out of the ground. Spray dicamba early in the growing season to avoid hot temperatures and take advantage of its residual activity. In XtendFlex systems, the best weed control has been achieved when dicamba was applied early followed by glufosinate (Liberty) 14 days later.
For the most up-to-date Arkansas weed science information, please make sure to:
- See the MP44 Recommended Chemicals for Weed and Brush Control,
- Listen to our Weeds AR Wild podcast series on Arkansas Row Crops Radio,
- Visit the UADA weed science website (https://www.uaex.uada.edu/weeds), and
- Subscribe to our text service by texting “weeds” to (501) 300-8883.