The 2019 Weed Control Manual for Tennessee Field Crops, Forage Crops, Pastures, Farm Ponds and Harvest Aids is now posted online. The major change to the 2019 manual is the addition of Engenia, XtendiMax and Fexapan in Xtend crops. The weed manual committee last year voted to not add this new use pattern of dicamba to the recommendations in the 2018 Weed Control Manual. However, with the widespread planting of these varieties in Tennessee, the committee has elected to add it in the 2019 version. One reason for this addition was to recommend best management practices (BMPs) to help avoid the off-target dicamba issues we have been plagued with over the past three years.
The recommendations on BMPs to steward these products are over and above what the labels for the respective herbicides state. 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 3 years on drift issues related to these herbicides.
The BMPs for stewardship in the comment section for Engenia, XtendiMax and Fexapan will state:
Applicators must take dicamba-specific training and be a certified applicator. The federal labeled cutoff for dicamba applications in Xtend soybean is R1 or 45 days after planting (whichever comes first) and 60 days after Xtend cotton planting. In addition to label requirements, the following best management practices are recommended by UT to minimize off-target movement. 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. Also, labels must be followed with great attention to detail. Spraying at night, wrong nozzles, off-label wind speed, excessive boom height, the addition of AMS to spray mixture, etc. could increase chances for off-target movement. Refer to the label or websites for more restrictions and information: