Pratap Devkota, Weed Scientist, UF/IFAS West Florida Research and Education Center
Enlist crop technology (2,4-D-tolerant) allows for the application of 2,4-D choline herbicide products on Enlist Cotton, Enlist Corn, and Enlist E3 Soybean. The newer 2,4-D choline formulation has very low volatility compared to the traditional 2,4-D formulations (such as amine, esters, etc.). Still, the concern with off-target injury to sensitive crops remains. In Florida, numerous crops are grown (such as soybean, cotton, snap bean, peanut, watermelon, cantaloupe, tomato, pepper, blueberry, pecans, etc.) which are sensitive to 2,4-D so proper measures should be taken before applying these herbicides. A good understanding of product selection, application rates, application timing, approved tank-mix partners, approved nozzle and pressure combinations, wind speed and spray application parameters, and sprayer cleanout procedures are all critical for safe use of Enlist herbicide products.
Herbicide Product Selection and Application
Currently, there are 2 products containing 2,4-D choline which can be applied on 2,4-D-tolerant crops (Enlist Crops). Enlist One only contains 2,4-D choline, while Enlist Duo contains a premix of 2,4-D choline plus glyphosate. The product selection can be made according to the individual field situation and weed problems. Enlist One does not provide any level of grass weed control, while Enlist Duo does provide grass weed control because it contains glyphosate. Due to endangered species concerns and new label restrictions, growers within Jackson and Santa Rosa counties cannot use Enlist Duo. These growers still have the ability to use Enlist One and can also legally add glyphosate to the tank, they just cannot use the pre-mix Enlist Duo. Other products containing 2,4-D (2,4-D Amine, LV4, 2,4-D Ester, etc.) cannot be applied on 2,4-D tolerant crops (Enlist Crops). There is crop specific information for Enlist One and Enlist Duo application, therefore, the herbicide label should be followed carefully, and proper precautions needs to be in place before applying these herbicides.
There are various herbicides or pesticide products which are compatible with Enlist One or Enlist Duo herbicides. Only products recommended in the Enlist One or Enlist Duo label can be safely tank-mixed. Ammonium sulfate (AMS) is a recommended product for Enlist One or Enlist Duo application, so appropriate AMS products can be used as a water conditioning agent. If incompatible products are tank-mixed, it can result in a significant increase of 2,4-D volatility and potential off-target crop/plant injury. The list of recommended tank-mix products for Enlist One and Enlist Duo herbicides can be found using the links below.
A 30-feet downwind buffer to sensitive area/crops is required for Enlist One and Enlist Duo applications. Application swath cannot be initiated within 30 feet of any downwind sensitive areas. Even with the appropriate buffer distance in place, the safe practice to prevent off-target injury is not to spray when wind is blowing towards a sensitive crop.
Like with newer dicamba products, only qualified nozzles should be used with the corresponding pressure ranges for Enlist One or Enlist Duo herbicide applications. The use of unqualified nozzles can result in a higher percentage of driftable particles and cause significant off-target injury. The details regarding allowed nozzles and pressure combinations for Enlist One and Enlist Duo herbicides can be found using the links provided below. Note that use of any nozzle not specifically approved and listed on these websites would be considered a misuse.
In the presence of wind, increased boom height increases the travel distance for a spray droplet. So, the higher boom height the greater the potential for drift. With appropriate boom height, the droplet is less likely to travel longer distances, thus reducing drift potential. A maximum boom height of 24 inches above the target weed/crop canopy is recommended for applying Enlist One or Enlist Duo herbicides.
Wind Speed and Direction
Even though the Enlist One and Enlist Duo herbicide labels include a maximum wind speed of 15 mph, it is essential to pay close attention to wind speed and direction requirements for Florida Organo-Auxin Rule. The Florida Organo-Auxin Rule prohibits application of synthetic organo-auxin herbicides (such as 2,4-D, dicamba, etc.) if wind is blowing towards sensitive crops at the speed/gusts above 10 mph (FDACS 2021). At higher wind speeds, spray droplets will move farther and increase drift potential.
Temperature Inversion Condition
Enlist One and Enlist Duo herbicides should never be sprayed if conditions near the soil surface are favorable for a temperature inversion. If sprayed during temperature inversion conditions, there is significant risk for off-target herbicide movement and crop injury. Cool conditions near the ground, low laying layer of fog, or presence of dew represent temperature inversion conditions. The temperature inversion condition is usually common during early morning or late part of the day but can also occur during the afternoon.
After applying Enlist One or Enlist Duo herbicide, the sprayer should be thoroughly cleaned following the Triple-Rinse procedure as outlined in the Label or Enlist Product Use Guide. The entire sprayer including tank, boom, hoses, connections, nozzles/screens, etc. should be cleaned properly to avoid the chance of spray contamination. If another tank-mixed product has a more stringent sprayer cleanout requirement, then follow that procedure. Do not let herbicide solution sit in the sprayer overnight or for extended hours.
According to the FDACS Organo-Auxin Rule, record keeping is mandatory for 2 years for synthetic organo-auxin herbicides if applied to more than 5 acres in a 24-hour window (this is a common scenario for crop field applications). The record keeping should contain the information as outlined on the rule which can be found with link below.