Wet and cold with more rain in the forecast. Ugg! That sums up our spring planting season to date. Hopefully, next week, we will get our break and can get a good bit done in the field. When that time comes, please remember to use best management practices applying all herbicides but particularly dicamba containing products!
A deadline that is coming up quickly is the Tennessee State rule that prohibits the use of older generic formulations of dicamba in soybean or cotton from May 15 to October 1. The dicamba formulations prohibited would include Banvel, Clarity, Sterling Blue, Strut, etc. after May 15.
This rule is designed to stop the use of the older more volatile dicamba formulations used as a burndown before planting soybean or cotton later in the growing season. Rather, after May 15 only the dicamba formulations Engenia, FexaPan, Tavium and XtendiMax can be used for burndown. Also, they are still legal to use PRE and POST in Xtend soybean and cotton varieties.
Just as a reminder some of the best management practices (BMPs) for dicamba stewardship can be found here at the Tennessee Department of Agriculture’s Dicamba Resources page.
The 2020 Weed Control Manual for Tennessee Field Crops, Forage Crops, Pastures, Farm Ponds and Harvest Aids is on in print and posted online. BMPs can also be found in this publication as well in the comment section for Engenia/XtendiMax/FeXaPan/Tavium.
In that section one can see some additional BMPs (below) over and above what can be found on the label. These recommendations were formulated from the University of Tennessee weed manual committee. The reason for these additional recommendations was to help avoid the off-target dicamba issues we have been plagued with over the past four years.
The weed manual committee consists of Drs. Neil Rhodes, Bob Hayes, Scott Senseman, Blake Brown, Angela McClure, Tom Mueller, Barry Sims and myself. Collectively, we have well over 250 years of weed management experience. Two of the members, Dr. Tom Mueller and Dr. Scott Senseman, have between them conducted herbicide fate research for over 50 years.
The recommendations below are based on this collective experience, considerable dicamba off-target research by Dr. Mueller, and finally well over 400 field visits we have made in the last 4 years on drift issues related to these herbicides.
The UT BMPs for stewardship in the comment section for Engenia, Fexapan, Tavium, XtendiMax states:
UT research suggests that dicamba-based herbicides are more prone to off-target movement as air temperature increases. Therefore, best management practices to minimize drift are to only apply if the expected high temperature of the day is less than 85°F or before June 15, whichever is more restrictive.
UT research also indicates that tankmixing glyphosate with these low-volatile dicamba formulations will lower the tank solution pH which can result in increased dicamba emissions. Despite many applicators’ best efforts with applications, off-target movement has apparently occurred with these products in multiple directions from treated fields independent of wind direction. Do not apply if sensitive crops or plants are in adjacent fields.