NAAA’s Dr. Scott Bretthauer spoke on January 31 at a special
symposium at the 2018 Annual meeting of the Weed Science Society of America in
Arlington, Virginia. The symposium was entitled “Fostering Sustainable Programs
to Improve Pesticide Applications and Promote Resistance Management”, and the
goal of the symposium was to foster cooperation among academics, industry,
growers, and the U.S. EPA for managing off-target pesticide movement and
managing herbicide resistance. NAAA was invited by session organizer Rick
Keigwin, director of EPA’s Office of Pesticide Programs to discuss the benefits
of agricultural aviation and some of the technologies and techniques used by
agricultural aviators to make on-target aerial applications.
Dr. Bretthauer began by discussing the many benefits aerial
applications offer for making pesticide applications, including timeliness of
applications and the ability to treat a crop when the ground is wet. One issue
often discussed by weed scientists is the importance of spraying weeds when
they are small, which is often not accomplished for a variety of reasons. These
reasons include the need to treat many acres in a small amount of time and poor
weather conditions that keep ground rigs out of fields. He stressed that aerial
applicators have the ability to get far more acres treated in a given period of
time than ground rigs and should be used more often to make certain herbicide
applications are made when weeds are smaller and easier to control.
Next, he discussed how aerial applicators select nozzles and
set them up to create the desired droplet size. He provided examples of the
variables that determine droplet size including nozzle type, orifice size, operating
pressure, and deflection angle. The USDA-ARS Aerial Application Technology Research
Unit’s spray droplet models were used to highlight key points for aerial nozzle
selection and show how certain factors can be used to make droplets appropriate
for herbicide applications. He emphasized that agricultural aircraft can be set
up to create coarse or larger droplet spectrums, and provided an example of a
setup that would provide a coarse droplet at 160 mph.
NAAA’s Dr. Scott Bretthauer
speaking at the 2018 Annual meeting of the
Weed Science Society of America in Arlington, Virginia.
The impact of reducing boom length relative to wingspan and
rotor diameter on reducing the potential for drift was discussed next. Results
from pattern testing, the AgDISP model, and drift research highlighted how
shortening the boom can mitigate drift while only making a slight reduction in
productivity. It was pointed out that using a shortened boom was a topic of the
PAASS program in 2017-2018 and that the audience response polling indicated a
strong interest in this concept. Use of a right-hand boom shut-offs as a drift
mitigation tool was also covered. Dr. Bretthauer finished up discussing two
other advantages aerial applicators have over ground rigs – the ability to
monitor weather conditions on site and the ability to make multiple applications
in order to use wind direction to avoid drift on sensitive areas.
