Aerial
Herbicide Applications
I received a call asking about the
potential for aerial herbicide applications as we battle the wet
field conditions. While it is true that some herbicide labels
have aerial application directions, I generally would not
recommend aerial herbicide application because of the increased
risk of off-target herbicide movement. The off-target movement
could either result from drift or accidental over-spray.
Unfortunately, I suspect that aerial applications may cause
neighbors to scrutinize the application more closely, looking
for damage from perceived or actual drift.
The only time that I would
consider aerial herbicide application in Wisconsin is if the
weather conditions (wind speed and direction, inversion
conditions), sensitive sites (who owns adjacent property, what
are the adjacent crops and other plants), herbicide, and
applicator’s skills are fully assessed and you are fully
confident that there is no risk. In this case, thinking that an
aerial application "should be okay" is not good
enough. Remember that aerial applications are releasing
herbicide droplets at a height measured in feet compared to
ground applications where that height is inches. The increased
height increases the potential for lateral movement before the
droplets land on a plant. In addition, the vortices at the wing
tips can pull droplets even higher into the air.
As a quick summary of some of the
postemergence corn herbicides, the labels of Accent, Aim, Basis
Gold, Clarity, Northstar, Steadfast, Roundup UltraMax, and
Touchdown actually have use directions for aerial applications
on their labels. However, I don’t think these aerial
application directions were necessarily written anticipating
Wisconsin conditions. I expect the large fields in states like
Kansas or Nebraska were the reason for including aerial
applications on these labels. I would never recommend aerial
applications of some herbicides in Wisconsin. The first one I
would avoid is dicamba because of the low concentrations that
can cause symptoms. Note that Clarity and Northstar both contain
dicamba. I would also be extremely reluctant to aerially apply
glyphosate products.
Accent Gold, Celebrity Plus,
Distinct, Liberty are examples of some corn labels that do not
have directions for aerial application, but aerial applications
are not specifically prohibited. Hornet is prohibited from being
applied aerially. I did not make a comprehensive list of
herbicides that can and cannot be applied aerially because I
want you to check the specific label for all of the directions
if you proceed with an aerial application. These herbicides were
mentioned just to give a sense of what may exist on the labels.
Bottom line: Although some labels
have directions for aerial application, I would be extremely
reluctant to recommend aerial applications in Wisconsin
considering our field sizes and the number of sensitive sites
and crops adjacent to sprayed fields. Considering drift problems
that occasionally happen with ground applications, imagine the
risk with aerial herbicide applications, especially with their
excellent postemergence activity.
June 2001 |
