Exceptions to the “Rules” A schematic of an aerial RAAT ...wci.colostate.edu/Assets/pdf/aerial.pdf · Grasshopper Management Board: tional approach of using 16 fluid ounces per

ReducedAgent

and

AreaTreatments

(RAATs)

A schematic of an aerial RAAT applicationwith 50% coverage.

Untreated - 100 ft.

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Untreated - 100 ft. ! !

100 ft. - Treated

Do morewith less

using

A E R I A L - R A A T S T R A T E G Y

An IPM strategy for rangelandgrasshopper infestations -

an economical and environmentalwin-win approach to pest

management

4 Experimental applications have demonstratedthat Dimilin-RAATs provide more than 90percent mortality when ground temperaturesexceed air temperatures by as much as 15°F.Extensive research in Australia has demonstratedthat when ground temperatures exceed airtemperatures, thermal updrafts can limit insecti-cide deposition of aerial applications unless thereare winds of 2 to 10 miles per hour (ideally,perpendicular to the swaths). Oil adjuvants inthe insecticide carrier will ensure that evapora-tion will not cause application failure.

5 Using canola or corn oil rather than crop oil asa carrier may significantly improve the effective-ness of RAAT applications. Canola and corn oilsare effective attractants and feeding stimulantsfor many rangeland grasshopper species. Toemulsify the oil with water use a minimum ofone part crop oil concentrate to seven partscanola or corn oil.

6 Small-scale trials under optimal conditionsindicate that 80 to 85% grasshopper control canbe achieved using 100-foot swaths with thefollowing rates and coverages: 5 fluid ounces peracre with 33-foot untreated swaths, 6 ounceswith 50-foot untreated swaths, and 7 ounceswith 100-foot untreated swaths. It is alsopossible to use 4 ounces of canola oil combinedwith 4 ounces of malathion with 100-foottreated and untreated swaths.

Exceptions to the “Rules”Higher rates and/or coverages may be needed if:

1. treatments are applied to late instarnymphs (especially if using Dimilin® 2L),

2. ground temperatures exceed air tempera-tures (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 toassess program options. Always apply insecti-cides in accordance with label directions andestablished guidelines for buffers aroundwater, bees, and human habitations.

¹For more information on RAATs or to down-load CARMA, visit: www.wygisc.uwyo.edu/grasshopper/

²Available from the USDA-ARS Northern PlainsAgricultural Research Laboratory at:

www.sidney.ars.usda.gov/grasshopper/Support/Hopper.htm

or contact:

Assistant Professor Alexandre LatchininskyAssociation for Applied Acridology International

andRenewable Resources - EntomologyDept. 3354, University of Wyoming

1000 E. University Ave.Laramie, WY 82071

Phone (307) 766-2298; Fax (307) 766-5025;e-mail [email protected]

MP-952004

Funding for RAAT research has been providedby the state of Wyoming (legislature, depart-ment of agriculture, weed and pest districts,University of Wyoming), U.S. Department ofAgriculture (Western Regional IPM Project,APHIS, and CSREES), and cooperatingindustries.

The information given herein is for educationalpurposes only. References to commercial products ortrade names are made with the understanding thatno discrimination is intended and no endorsementby the Cooperative Extension Service is implied.

Persons seeking admission, employment, or access toprograms of the University of Wyoming shall beconsidered without regard to race, color, nationalorigin, sex, age, religion, political belief, disability,veteran status, and marital or familial status.

100 ft. - Treated

100 ft. - Treated

3

2

1

What are RAATs?RAATs are a method of integrated pestmanagement (IPM) for rangeland grasshop-pers in which the rate of insecticide is reducedfrom levels recommended by the label anduntreated swaths (refuges) are alternated withtreated swaths.

RAATs work through chemical control,meaning grasshoppers are killed in treatedswaths and as they move out of untreatedswaths, and conservation biological control,which allows predators and parasites preservedin untreated swaths to suppress grasshoppers.This IPM approach can reduce the cost ofcontrol and the amount of insecticide used bymore than 50 percent.

Why use RAATs?EconomicsInflation and the restructuring of the USDAcost-share program have tripled the cost ofrangeland grasshopper management forranchers compared with the control cost duringthe last major outbreak in the late 1980s. Moststates no longer subsidize grasshopper pro-grams; therefore, the cost of traditional controltactics will usually exceed the benefits. Eventhough certain federal or state subsidies for

grasshopper control are becoming available insome states, the expenses of a managementprogram remain largely a producer’s burdenbecause of high insecticide and treatment costs.

EnvironmentLess insecticide in the environment lowers therisk to native plant and animal species (includ-ing fish and wildlife), water quality, andhumans. The untreated swaths provide arefuge for organisms with lower mobility thangrasshoppers, and even those organisms thatmove into the treated swaths will be largelyunaffected 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 Aerial-RAATsEfficacyThis method will normally result in 80 to 95%control, which is approximately a 5 to 15% lowermortality than with a conventional (higher rate,blanket coverage) treatment. Leaving low,residual densities of grasshoppers after RAATsdoes not necessarily result in a subsequentoutbreak (see Environment below).

EconomicsUsing RAATs will greatly reduce the cost ofcontrol programs, depending on the agent and

swath width. In some cases, costs are reducedby two-thirds. It should be noted that thegreatest economic benefits derive from increasedswath spacing since this effectively decreasesboth the cost of insecticide and application.

EnvironmentRAATs mean 50 to 75% less insecticide isapplied to our rangelands for grasshoppercontrol. The untreated swaths harbor speciesessential to rangeland ecosystems includingbiocontrol agents of grasshoppers and weeds.Low densities of surviving grasshoppers allowpredators and parasites in the untreatedrefuges to recolonize and thereby reestablishnatural regulation of grasshopper populations.For these reasons, RAAT programs may alsoallow for higher densities of birds than blanketapplications.

How to use RAATsResearch conducted from 1995 to 2003 byUniversity of Wyoming and USDA scientists, incooperation with state departments of agricul-ture and weed and pest districts, has involved260 experimental plots of 40 acres each and 19operational trials on 640-acre areas at densitiesof 7 to 70 grasshoppers per square yard.Successful operational RAAT programs havebeen conducted in 10 western states. Thefollowing tactics most often optimize economicreturns and are recommended by the NationalGrasshopper Management Board:

tional approach of using 16 fluid ouncesper acre in a blanket coverage).

2. Apply4 diflubenzuron (Dimilin® 2L) at arate of 0.75 fluid ounce (=5.3 grams ofactive ingredient) per acre with 8 fluidounces of water and 4 fluid ounces of oiladjuvant in 100-foot swaths3, alternatingwith 100-foot untreated swaths, OR applyat a rate of 1 ounce per acre with 16ounces of water and 8 ounces of canola orcorn oil5 in 100-foot swaths3, alternatingwith 200-foot untreated swaths (comparedwith the conventional approach of using 1fluid ounce per acre in a blanket coverage).

3. Apply malathion (Fyfanon® ULV) at arate of 4 fluid ounces (=138 grams ofactive ingredient) per acre in 100-footswaths3, alternating with 25-foot un-treated swaths6 (compared with theconventional approach of using 8 fluidounces per acre in a blanket coverage).

1. Apply carbaryl (Sevin® XLR Plus) at arate of 8 fluid ounces (=113 grams ofactive ingredient) per acre with an equalvolume of water1,2 at pH#7 in 100-footswaths3, alternating with 100-foot un-treated swaths (compared with the conven-

1 This low volume (16 fluid oz. total) method hasbeen adopted on the product label for RAATs.

2 Increasing the volume of water above the 1:1ratio with carbaryl will not improve and mayreduce efficacy and washoff resistance. Alkalinewater should be buffered to neutral to preventchemical degradation of carbaryl.

3 Wider treated swaths (>100 foot) may be useddepending on the spraying equipment. While itmay be possible to proportionately expanduntreated swaths, this approach has not beentested. Therefore, the most prudent tactic atthis time would be to maintain the fixed widthsof the recommended untreated swaths, whichshould never exceed 200 feet in any case.