Do more
with less, using Reduced Agent and Area Treatments (RAATs)
Aerial-Applied Strategies
by Dr. Jeffrey A
Lockwood and Dr. Alexandre Latchininsky, University of Wyoming
Download the PDF Version of
the 2004 Aerial RAATs brochure
Download the PDF Version of the 2004
ATV-RAATs brochure
• What is RAATs?
• Why Use RAATs?
• What to expect from RAATs
• How to use RAATs
• The Future of RAATs
Research and Development
• Exceptions to the "Rules"
What are RAATs?
RAATs are a method of integrated pest
management (IPM) for rangeland grasshoppers in which the rate of
insecticide is reduced from levels recommended by the label and
untreated swaths (refuges) are alternated with treated swaths.
RAATs work through chemical control,
meaning grasshoppers are killed in treated swaths and as they move
out of untreated swaths, and conservation biological control, which
allows predators and parasites preserved in untreated swaths to
suppress grasshoppers. This IPM approach can reduce the cost of
control and the amount of insecticide used by more than 50 percent.
Why
Use RAATs?
Economics
Inflation and the restructuring of the USDA cost-share program
have tripled the cost of rangeland grasshopper management for
ranchers compared with the control cost during the last major
outbreak in the late 1980s. Most states no longer subsidize
grasshopper programs; therefore, the cost of traditional control
tactics will usually exceed the benefits. Even though certain
federal or state subsidies for grasshopper control are becoming
available in some states, the expenses of a management program
remain largely a producer’s burden because of high insecticide and
treatment costs.
Environment
Less insecticide in the environment lowers the risk to native
plant and animal species (including fish and wildlife), water
quality, and humans. The untreated swaths provide a refuge for
organisms with lower mobility than grasshoppers, and even those
organisms that move into the treated swaths will be largely
unaffected unless they feed on the foliage. RAATs are the preferred
option in the USDA-APHIS EIS if grasshopper control is required.
What
to expect from RAATs
Efficacy
This method will normally result in 80 to 95% control, which is
approximately a 5 to 15% lower mortality than with a conventional
(higher rate, blanket coverage) treatment. Leaving low, residual
densities of grasshoppers after RAATs does not necessarily result in
a subsequent outbreak (see Environment below).
Economics
Using RAATs will greatly reduce the cost of control programs,
depending on the agent and swath width. In some cases, costs are
reduced by two-thirds. It should be noted that the greatest economic
benefits derive from increased swath spacing since this effectively
decreases both the cost of insecticide and application.
Environment
RAATs mean 50 to 75% less insecticide is applied to our rangelands
for grasshopper control. The untreated swaths harbor species
essential to rangeland ecosystems including biocontrol agents of
grasshoppers and weeds. Low densities of surviving grasshoppers
allow predators and parasites in the untreated refuges to recognize
and thereby reestablish natural regulation of grasshopper
populations. For these reasons, RAAT programs may also allow for
higher densities of birds than blanket applications.
How
to use RAATs
Aerial-Applied Reduced Agent and Area Treatment (RAAT) Strategies
Download PDF version (PDF) of
2004 Aerial RAATs brochure
Research conducted from 1995 to 2003
by University of Wyoming and USDA scientists, in cooperation with
state departments of agriculture and weed and pest districts, has
involved 260 experimental plots of 40 acres each and 19 operational
trials on 640-acre areas at densities of 7 to 70 grasshoppers per
square yard. Successful operational RAAT programs have been
conducted in 10 western states. The following tactics most often
optimize economic returns and are recommended by the National
Grasshopper Management Board:
1. Apply carbaryl (Sevin® XLR Plus) at
a rate of 8 fluid ounces (=113 grams of active ingredient) per acre
with an equal volume of water1,2 at pH#7 in 100-foot swaths3,
alternating with 100-foot untreated swaths (compared with the
conventional approach of using 16 fluid ounces per acre in a blanket
coverage).
2. Apply4 diflubenzuron (Dimilin® 2L)
at a rate of 0.75 fluid ounce (=5.3 grams of active ingredient) per
acre with 8 fluid ounces of water and 4 fluid ounces of oil adjuvant
in 100-foot swaths3, alternating with 100-foot untreated swaths, OR
apply at a rate of 1 ounce per acre with 16 ounces of water and 8
ounces of canola or corn oil5 in 100-foot swaths3, alternating with
200-foot untreated swaths (compared with the conventional approach
of using 1 fluid ounce per acre in a blanket coverage).
3. Apply malathion (Fyfanon® ULV) at a
rate of 4 fluid ounces (=138 grams of active ingredient) per acre in
100-foot swaths3, alternating with 25-foot untreated swaths6
(compared with the conventional approach of using 8 fluid ounces per
acre in a blanket coverage).
1 Apply carbaryl (Sevin® XLR Plus) at
a rate of 8 fluid ounces (=113 grams of active ingredient) per acre
with an equal volume of water1,2 at pH#7 in 100-foot swaths3,
alternating with 100-foot untreated swaths (compared with the conven-
1 This low volume (16 fluid oz. total) method has been adopted on
the product label for RAATs.
2 Increasing the volume of water above
the 1:1 ratio with carbaryl will not improve and may reduce efficacy
and washoff resistance. Alkaline water should be buffered to neutral
to prevent chemical degradation of carbaryl.
3 Wider treated swaths (>100 foot) may
be used depending on the spraying equipment. While it may be
possible to proportionately expand untreated swaths, this approach
has not been tested. Therefore, the most prudent tactic at this time
would be to maintain the fixed widths of the recommended untreated
swaths, which should never exceed 200 feet in any case.
4 Experimental applications have
demonstrated that Dimilin-RAATs provide more than 90 percent
mortality when ground temperatures exceed air temperatures by as
much as 15°F. Extensive research in Australia has demonstrated
that when ground temperatures exceed air temperatures, thermal
updrafts can limit insecticide deposition of aerial applications
unless there are winds of 2 to 10 miles per hour (ideally,
perpendicular to the swaths). Oil adjuvants in the insecticide
carrier will ensure that evaporation will not cause application
failure.
5 Using canola or corn oil rather
than crop oil as a carrier may significantly improve the
effectiveness of RAAT applications. Canola and corn oils are
effective attractants and feeding stimulants for many rangeland
grasshopper species. To emulsify the oil with water use a
minimum of one part crop oil concentrate to seven parts canola
or corn oil.
6 Small-scale trials under optimal
conditions indicate that 80 to 85% grasshopper control can be
achieved using 100-foot swaths with the following rates and
coverages: 5 fluid ounces per acre with 33-foot untreated
swaths, 6 ounces with 50-foot untreated swaths, and 7 ounces
with 100-foot untreated swaths. It is also possible to use 4
ounces of canola oil combined with 4 ounces of malathion with
100-foot treated and untreated swaths.
The
Future of RAATs
Research and Development
1. Enhancing the efficacy of RAATs using vegetable oils as carriers
of carbaryl and diflubenzuron (several oils are attractants and
feeding stimulants for rangeland grasshopper species)
2. Refining the parameters of a Dimilin-RAAT program, including
minimizing total volume, optimizing the oil:water ratio, and identifying
the best oil to use as a carrier
3. Accelerating the optimization of RAATs programs through ecological
modeling of the complex biological and physical factors that determine
efficacy
Exceptions to the "Rules"
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A schematic of an
aerial RAAT application
with 50 percent coverage.
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Higher
rates and/or coverages may be needed if:
1.
treatments are applied to late instar nymphs (especially if using
Dimilin® 2L)
2. ground temperatures exceed air temperatures (especially if using
malathion)
3. grasshopper densities are extreme (e.g., >40 per square yard)
4. forage cover is tall and/or dense, and
5. terrain is rough.
In all
cases, grasshopper management software (CARMA¹ or HOPPER²) should be
used to assess program options. Always apply insecticides in
accordance with label directions and established guidelines for
buffers around water, bees, and human habitations.
¹For more information on RAATs or to download CARMA, visit:
www.wygisc.uwyo.edu/grasshopper/
²Available from the USDA-ARS Northern Plains Agricultural Research
Laboratory at:
www.sidney.ars.usda.gov/grasshopper/Support/Hopper.htm
For more information and updates, visit our Web Site at
www.sdvc.uwyo.edu/grasshopper/raats.htm or contact
Assistant Professor Alexandre
Latchininsky, Association for Applied Acridology International
and Department of Renewable Resources, College of Agriculture,
University of Wyoming, P.O. Box 3354, 1000 E. University Ave.,
Laramie, WY 82071-3354, phone (307)766-4260, and fax (307)766-5025.
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