1. Consult Product Labels
Labels for the new dicamba formulations are similar but not the same. Read them closely before you head to the field.
2. Choose Your Nozzle Wisely
The new dicamba formulation labels specify nozzles that you can use for applications, and they do for good reason. Despite manufacturers’ best efforts, dicamba still has the potential to drift or volatilize and put sensitive crops in fields nearby at risk.
Until a few weeks ago, only one spray nozzle, the Tee Jet TTI11004, had been approved for applications. Now, depending on the formulation, you have at least 20 nozzles from five different companies from which to choose.
These nozzles were approved with drift reduction in mind. They produce a small amount of driftable fines (some have shown to produce less than 2%), and they create coarse to ultra-coarse droplets for good weed coverage.
Nozzle selection is important, but you still need to calibrate sprayers to optimize herbicide performance and minimize drift potential. Be sure to maintain routine inspections during application season as well. Be diligent, and replace any nozzles that show wear or damage.
3. Beware of Wind
Wind is not Your Friend
Being aware of your local weather conditions is critical before and during the application of any dicamba product, according to Robert Wolf, On Target Application Academy (OTAA) trainer for BASF and professor emeritus at Kansas State University.
“Wind is the No. 1 concern the industry has for off-target movement,” he says.
Portable wind speed indicators are the best tool for determining wind speed, Wolf notes. He recommends measuring it often, based on the size of the job, and checking wind direction. He says it’s best to use the wind speed indicator at boom height, so you’re measuring wind speed at the product release height from the nozzles. Placing small colored flags in the field can help you to determine wind direction.
For added safety, Wolf says, “I also recommend using a compass, so applicators can properly record the degrees on it; that indicates the direction the wind is coming from, so applicators can be well-protected in their recordkeeping process.”
Buffers between dicamba-sprayed fields and surrounding crops are also an important consideration, says Alan York, North Carolina State University Extension weed specialist emeritus. His specific concern: “The labels do not mention a ‘safe’ distance between application site and sensitive crops.”
Wolf encourages applicators to consult sensitive crop registries for their areas prior to spraying.
4. Consider Application Timing
A warm, sunny, late afternoon might seem like prime time to apply one of the new dicamba formulations, but that wouldn’t necessarily be the case.
An application then could result in damaging, long-distance movement caused by a temperature inversion.
A temperature inversion occurs when warm air, which is light, rises upward into the atmosphere, and cool air, which is heavy, settles near the ground. When warm air hangs above cool air, the two won’t mix. So if you’ve made a dicamba application (some other pesticides are also affected), spray droplets are unlikely to disperse. Instead, they’ll stay bunched in a concentrated mass, and even slight airflow could move them off-target.
Temperature inversions often occur between 5 p.m. and 7 p.m. Tell-tale signs are dust or fog hanging over a road or field. They typically break up at sunrise with increased wind (above 3 mph) or as surface air warms (3°F increase from the morning low).
By Rhonda Brooks, Editor, AgPro
rbrooks@farmjournal.com
