What are the NEW label restrictions and guidelines for Dicamba in soybeans?
Sandra Wick, Crop Production Agent
How can you tell in the field if an inversion is present? More often than not, there is no simple way to determine the presence of an inversion. You absolutely must take temperature measurements at two different heights to determine the change in temperature with height. Occasionally, there are some visual indicators of an inversion. A few indicators might be low lying fog in valleys, low points, and over different ground cover along with frost or dew on the ground.
Well, I’m sure some of your soybean fields might have been affected this last growing season with the chemical dicamba. Several reports of non-Xtend soybeans expressed some kind of damage. Most producers have probably already heard that EPA, and the companies selling dicamba products registered for use on Xtend soybeans and other crops, have reached an agreement on label modifications and application requirements to try and further minimize the potential for off-target damage to susceptible crops. Below is a brief summary of the key changes to the Xtendimax, Fexapan, and Engenia product labels according to KSU weed specialists:
- All products will be classified as “restricted use”, permitting only certified applicators to purchase and apply or supervise the application of the products.
- Supplemental labeling will be incorporated into the regular labels, and application guidelines will be the same for all uses, including dicamba and non-dicamba tolerant crops.
- Applicators must complete dicamba or auxin-specific training prior to application.
- Requires more specific record keeping of applications, including checking for the presence of sensitive crops in the area.
- Do not spray when wind is blowing in the direction of neighboring sensitive crops, including non-Xtend crops. The label more clearly states that this restriction includes non-Xtend soybeans.
- Restricts applications to wind speeds between 3 and 10 mph. Reduced maximum wind speed from 15 mph in 2017 and prohibits all applications at less than 3 mph when temperature inversions are more likely to occur.
- Prohibits applications between sundown and sunrise. All applications prohibited during temperature inversions regardless of time of day.
- Restricts the maximum application ground speed to less than 15 mph, with 5 mph recommended on field edges.
- Thoroughly clean spray equipment before and after application. Must be documented.
- Use an approved buffering agent if the water source or tank mix components result in an acidic spray solution less than pH 5.
In addition, remember that AMS is not allowed with any of these products because it greatly increases the volatility of dicamba. Approved tank-mixes, adjuvants, spray tips, and maximum pressures are still presented at the corresponding websites for each respective product as listed below:
Xtendimax: www.xtendimaxapplicationrequirements.com
Engenia: www.engeniatankmix.com
There is still a great deal of debate in the scientific community about the degree of vapor drift that might be occurring from dicamba applications. Most of the new application guidelines are directed more towards minimizing physical spray drift vs vapor drift. The time-of-day restrictions are intended to help reduce applications during temperature inversions which could result in greater off-target movement from both fine droplets and vapor. Be aware that the majority of problems seemed to occur from post-emergence applications made after soybeans were emerged and during warmer conditions. Applications earlier in the season may help minimize off-target issues.
So what are temperature inversions? In the troposphere, the lowest layer of the atmosphere that reaches the earth’s surface, temperature typically declines as altitude increases. This rough estimation of temperature with height doesn’t always fit the situation due to weather, terrain, and solar radiation. Anomalies in the lowest layer of the atmosphere occur when temperatures increase with height due to these factors. These anomalies are called inversions. When cooler, higher density air, is in place under warm, less dense air the atmosphere can behave much differently than expected. These differences include poor air dispersion, light winds, and fog.
How can you tell in the field if an inversion is present? More often than not, there is no simple way to determine the presence of an inversion. You absolutely must take temperature measurements at two different heights to determine the change in temperature with height. Occasionally, there are some visual indicators of an inversion. A few indicators might be low lying fog in valleys, low points, and over different ground cover along with frost or dew on the ground.
The KSU Weather Data Library does have stations around the state of Kansas that NOW provides these different height temperatures on the “Mesonet.” Our Post Rock Extension District stations are in Jewell, Mitchell and Osborne counties. The KSU Mesonet “inversion” data website is http://mesonet.k-state.edu/agriculture/inversion/.
KSU weed specialists stress to keep in mind that additional restrictions may be implemented by state regulatory agencies. If you have further questions on chemical restrictions, contact me at any Post Rock Extension District Office in Beloit, Lincoln, Mankato, Osborne or Smith Center.
Post Rock Extension District of K-State Research and Extension serves Jewell, Lincoln, Mitchell, Osborne, and Smith counties. Sandra may be contacted at swick@ksu.edu or by calling Smith Center, 282-6823, Beloit 738-3597, Lincoln 524-4432, Mankato 378-3174, or Osborne 346-2521. Join us on Facebook at “Post Rock Extension” along with our blog site at “postrockextension.blogspot.com. Also remember our website is www.postrock.ksu.edu and my twitter account is @PRDcrops.
