The scientific community has examined the risks and benefits of Bt plants more than any other novel agricultural technology developed over the past two decades, as demonstrated by the vast body of literature, scientific discussions, and numerous public meetings facilitated by the EPA, the US Department of Agriculture, and the US Food and Drug Administration on this subject.We find the evidence to date supports the appropriate use of Bt corn as one component in the economically and ecologically sound management of lepidopteran corn pests.This article is from BioScience 51 (2001): 900, doi:10.1641/0006-3568(2001)051[0900:TICTAA]2.0.C. Posted with permission.</p

Barry, B. Dean

Buschman, Lawrent

Calvin, Dennis

Carpenter, Janet

Dively, Galen

Foster, John

Fuller, Billy

Hellmich, Richard

Higgins, Randall

Hunt, Thomas

Munkvold, Gary

Ortman, Eldon

Ostlie, Kenneth

Rice, Marlin

Roush, Richard

Sears, Mark

Shelton, Anthony

Siegfried, Blair

Sloderbeck, Phillip

Steffey, Kevin

Turpin, F. Tom

Wedberg, John

Digital Repository @ Iowa State University (ISU)

900 BioScience  •  November 2001/ Vol. 51 No. 11LettersWe agree with Obrycki et al. (2001) thata broad-based ecological approach fornew pest management technologies isdesirable, but we unanimously andstrongly disagree with some of their as-sumptions and conclusions about Btcorn.Bt corn is corn that has been geneticallyengineered to produce insecticidal pro-teins from the bacterium Bacillusthuringiensis. Because Bt corn is impor-tant for effective and ecologically soundmanagement of lepidopteran pests ofcorn, we provide here relevant data, someof which is new, to help clarify the issuesraised by Obrycki et al. (2001).Obrycki et al. (2001), citing Barry andDarrah (1991), claim that traditionalplant breeding has developed corn plantsthat adequately protect against Europeancorn borer. However, Barry and Darrah(1991) reported only “some resistance towhorl leaf feeding...[or] some resistanceto sheath and sheath collar feeding,”which is not comparable with the nearlycomplete protection provided by Bt corn.Carpenter and Gianessi (2001) estimatedthat, nationally, during “10 of the 13 yearsbetween 1986 and 1998, European cornborer infestations...were such that corngrowers would have realized a gain fromplanting Bt corn.” Similarly, theEnvironmental Protection Agency(USEPA 2000) estimated a net benefit togrowers of $8.18 per hectare on 8 millionhectares of Bt corn planted in 1999, or anational benefit of $65.4 million (USEPA2000). Even considering the inherentyear-to-year variability in pest populationdensity, the EPA estimated the annualbenefit to corn growers at $38–$219 mil-lion (USEPA 2001).Bt corn has proven to prevent yieldloss, reduce mycotoxin levels, and reducethe use of insecticides on corn (Munkvoldet al. 1999, Munkvold and Hellmich 2000,Carpenter and Gianessi 2001).Applications of foliar insecticides areused to control populations of Europeancorn borers and southwestern corn bor-ers on non-Bt corn. But they are not usedextensively because of difficulty in scout-ing and timing treatments to control thelarvae before they bore into the plant.Consequently, growers have enduredlower yields and higher mycotoxin levels.Obrycki et al. (2001) stated that “the useof transgenic corn will not significantlyreduce insecticide use in most of thecorn-growing areas of the Midwest.” Onthe contrary, a survey of Bt corn pro-ducers (n = 7265) from six states (Illinois,Iowa, Kansas, Minnesota, Nebraska, andPennsylvania) documents that growersdid reduce insecticide use for Europeancorn borer during the first three growingseasons after commercial introductionof Bt corn. Approximately half of thefarmers did not use insecticides to man-age European corn borers on their farms.Of those growers using insecticides dur-ing the previous 5 years for Europeancorn borer control, the percentage de-creasing their usage of pesticides duringthe 3-year period nearly doubled from1996 to 1998 (13.2% to 26.0%) (Hellmichet al. 2000). Take Iowa with 5 millionhectares of commercial corn as an aver-age example: With 30% of the hectaresplanted in Bt corn, allowing 26% of theBt producers to reduce or eliminateEuropean corn-borer insecticide use,hundreds of thousands of hectares werenot sprayed with a broad-spectrum in-secticide. This benefit is easily overlooked:Figure 2 in the article by Obrycki andcolleagues (2001) includes all insecti-cides, whereas most use was granular in-secticides for control of corn rootworms,Diabrotica spp. Considering the benefitspointed out above, concurrence withinthe scientific community that there arereal benefits to ecosystems and humanhealth, including those from a reductionin use of more broad-spectrum foliar in-secticides, becomes clear (AMA 2000,APS 2001, Pool and Esnayre 2000).In addition, contrary to concerns re-garding monarch butterflies (Losey et al.1999), comprehensive new studies showthat Bt corn pollen poses little risk tomonarchs on a national scale (Hellmichet al. 2001, Oberhauser et al. 2001,Pleasants et al. 2001, Sears et al. 2001,Stanley-Horn et al. 2001). Collectively,these results validate EPA’s original andsubsequent evaluations of the potentialrisks posed to nontarget butterflies andmoths. As for other potential nontargeteffects of Bt corn, the EPA risk assess-ments relied on laboratory and field trialdata from representative organisms thatare routinely used in assessment of eco-logical toxicity, including avian species(quail), aquatic species (catfish and daph-nia), beneficial insects (honeybee, para-sitic wasp, green lacewing, ladybird bee-tle), soil invertebrates (springtails andearthworms), and mammals (mice)(USEPA 1995, 2000, 2001). These testsrepresent toxicological endpoints for single-species components of a largerecological system and may not necessar-ily predict all possible interactions. YetLetters to the EditorBioScienceAttn: Science Editor1444 I St., NW, Suite 200Washington, DC 20005E-mail: bioscience@aibs.orgThe staff of BioScience reserves the right toedit letters for clarity without notifying theauthor. Letters are published as spacebecomes available.Transgenic Insecticidal Corn: The Agronomic and Ecological Rationale for Its Use at Iowa State University on October 20, 2014http://bioscience.oxfordjournals.org/Downloaded from 902 BioScience  •  November 2001 / Vol. 51 No. 11Lettersthey are important because they providea basis for establishing acute toxicity in indicator organisms and for developinglonger-term community studies. Onemust keep in mind, though—regardlessof whether one uses a resistant plant, a bi-ological control agent, an insecticide, acultural technique, or any other methodto control a pest—that if the pest popu-lation is reduced, there will be some im-pact on the biological community.Positive and negative impacts of newtechnologies must be compared withthose of existing technologies. All possi-ble impacts of any technology or farmingpractice are impossible to foresee, butwe can focus on known and probablerisks. When risks of a technology arecharacterized as low, based on actualdata, then the potential impact should beevaluated proportional to that level ofconcern. This reasonable approachshould reduce the chances of rejectingsafe technologies simply because theyare new and unfamiliar. Ultimately, thegoal is to replace current pest manage-ment practices with ones that are moreeconomical and sustainable, as well asenvironmentally safer. A dynamic equi-librium between benefits and risks will bedeveloped as a result of this ongoingprocess. Over time, this equilibrium willchange as improved practices are devel-oped. In the meantime, if unexpectedproblems should occur, failsafe mecha-nisms exist. Any pesticidal technologyregistered by the EPA can have its regis-tration suspended or canceled when anunreasonable adverse effect is identified.The scientific community has exam-ined the risks and benefits of Bt plantsmore than any other novel agriculturaltechnology developed over the past twodecades, as demonstrated by the vastbody of literature, scientific discussions,and numerous public meetings facili-tated by the EPA, the US Department ofAgriculture, and the US Food and DrugAdministration on this subject. We findthe evidence to date supports the appro-priate use of Bt corn as one componentin the economically and ecologicallysound management of lepidopteran cornpests.ELDON E. ORTMAN Agricultural Research Programs Purdue UniversityB. DEAN BARRYUS Department of Agriculture,Agricultural Research ServiceLAWRENT L. BUSCHMAN Department of Entomology Kansas State UniversityDENNIS D. CALVIN Department of Entomology Pennsylvania State UniversityJANET CARPENTER National Center for Food and Agricultural PolicyGALEN P. DIVELY Department of Entomology University of MarylandJOHN E. FOSTER Department of EntomologyUniversity of NebraskaBILLY W. FULLER Plant Science Department South Dakota State UniversityRICHARD L. HELLMICH US Department of Agriculture,Agricultural Research Service,and Department of Entomology Iowa State UniversityRANDALL A. HIGGINS Department of Entomology Kansas State UniversityTHOMAS E. HUNT Department of Entomology University of NebraskaGARY P. MUNKVOLD Department of Plant Pathology Iowa State UniversityKENNETH R. OSTLIE Department of Entomology University of MinnesotaMARLIN E. RICE Department of Entomology Iowa State UniversityRICHARD T. ROUSH Department of Applied and Molecular EcologyUniversity of AdelaideMARK K. SEARS Department of Environmental BiologyUniversity of GuelphANTHONY M. SHELTON Department of Entomology, NYSAESCornell UniversityBLAIR D. SIEGFRIED Department of Entomology University of NebraskaPHILLIP E. SLODERBECK Department of Entomology Kansas State UniversityKEVIN L. STEFFEY Department of Crop Sciences University of IllinoisF. TOM TURPIN Department of Entomology Purdue UniversityJOHN L. WEDBERG Department of Entomology University of WisconsinReferences cited[AMA] American Medical Association. 2000.Genetically modified crops and foods. Report10 of the Council on Scientific Affairs, pre-sented at the 2000 Interim AMA Meeting. (5October 2001; www.ama-assn.org/ama/pub/article/2036-4030.html#Recommendations)[APS] American Phytopathological Society. 2001.Genetically modified insect resistant corn:Implications for disease management. (5October 2001; www.apsnet.org/online/feature/BtCorn/Top.html) Barry D, Darrah LL. 1991. Effect of research oncommercial hybrid maize resistance toEuropean corn borer (Lepidoptera: Pyralidae).Journal of Economic Entomology 84:1053–1059.Carpenter JE, Gianessi LP. 2001. Agriculturalbiotechnology: Updated benefit estimates.National Center for Food and AgriculturalPolicy. (5 October 2001; www.ncfap.org/pup/biotech/updatedbenefits.pdf)Hellmich, RL, Rice ME, Pleasants JM, Lam WK.2000. Of monarchs and men: Possible influencesof Bt corn in the agricultural community. Pages85–94 in Proceedings of the Integrated CropManagement Conference; 29–30 November2000; Iowa State University Extension, Ames.Hellmich RL, Siegfried BD, Sears MK, Stanley-Horn DE, Mattila HR, Spencer T, Bidne KG,Daniels MJ, Lewis LC. 2001. Monarch larvaesensitivity to Bacillus thuringiensis purified pro-teins and pollen. Proceedings of the NationalAcademy of Sciences 98: 11925–11930.Losey JE, Rayor LS, Carter ME. 1999. Transgenicpollen harms monarch larvae. Nature 399: 214.Munkvold GP, Hellmich RL. 2000. Geneticallymodified, insect resistant maize: Implicationsfor management of ear and stalk diseases. (11October 2001; www.planthealthprogress.org/Current/reviews/maize/)Munkvold GP, Hellmich RL, Rice LG. 1999.Comparison of fumonisin concentrations inkernels of transgenic Bt maize hybrids andnon-transgenic hybrids. Plant Disease 83:130–138.Oberhauser, et al. 2001. Temporal and spatial over-lap between monarch larvae and corn pollen.Proceedings of the National Academy ofSciences 98: 11913–11918.Obrycki JJ, Losey JE, Taylor OR, Jesse LCH. 2001.Transgenic insecticidal corn: Beyond insectici-dal toxicity to ecological complexity. BioScience51: 353–361.Pleasants JM, Hellmich RL, Dively G, Sears MK,Stanley-Horn DE, Mattila HR, Foster JE, Clark at Iowa State University on October 20, 2014http://bioscience.oxfordjournals.org/Downloaded from November 2001 / Vol. 51 No. 11 •  BioScience 903LettersPL, Jones GD. 2001. Corn pollen depositionon milkweeds in and near cornfields.Proceedings of the National Academy ofSciences 98: 11919–11924.Pool R, Esnayre J, eds. 2000. The Future Role ofPesticides in US Agriculture.Washington (DC):National Academy Press. (5 October 2001;http://books.nap.edu/books/0309065267/html/)Sears MK, Hellmich RL, Siegfried BD, PleasantsJM, Stanley-Horn DE, Oberhauser KS, DivelyGP. 2001. Impact of Bt corn pollen on monarchbutterfly populations: A risk assessment.Proceedings of the National Academy ofSciences 98: 11937–11942.Stanley-Horn DE, Dively GP, Hellmich RL, MattilaHR, Sears MK, Rose R, Jesse LCH, Losey JE,Obrycki JJ, Lewis LC. 2001.Assessing the impactof Cry1Ab-expressing corn pollen on monarchbutterfly larvae in field studies. Proceedings ofthe National Academy of Sciences 98:11931–11936.[USEPA] US Environmental Protection Agency.1995. Pesticide fact sheet for Bacillus thuringien-sis susp. kurstaki CryI(A)b delta-endotoxin andthe genetic material necessary for the produc-tion (plasmid vector pCIB4431) in corn.Washington (DC): USEPA. EPA731-F-95-004.———, Office of Pesticide Programs, Biopesticidesand Pollution Prevention Division. 2000.Biopesticides Registration Document;Preliminary Risks and Benefits Sections; Bacillusthuringiensis Plant-Pesticides. Washington(DC): USEPA.———. 2001. Biopesticides Registration ActionDocument; Revised Risks and Benefits Sections;Bacillus thuringiensis Plant-Pesticides.Washing-ton (DC): USEPA.Response from Obrycki and colleagues:We agree with our colleagues (Ortman etal.) that the appropriate use of Bt trans-genic corn can be one component in aneconomically and ecologically soundmanagement program for lepidopterancorn pests. However, we disagree that thecurrent use of Bt corn represents eco-logically based management of lepi-dopteran pests of corn. We argue thatplanting 20%–30% of the corn acreagewith Bt corn as a prophylatic treatmentfor lepidopteran pests is not ecologicallybased management. This approach isanalogous to continuous spraying of upto 30% of the field corn in the UnitedStates with a selective insecticide everyyear, just in case there is an infestation bya lepidopteran pest.We acknowledge that this technologyis relatively new, and that data being col-lected will provide a clearer understand-ing of the benefits and risks of trans-genic Bt corn. For example, a recent studyhas determined that nine transgenic Btcorn hybrids, developed from two sepa-rate transformation events, have signifi-cantly higher lignin levels than isogenichybrids (Saxena and Stotzky 2001). Wewelcome the engagement of our col-leagues in meaningful discussions of thistechnology and its role in pest manage-ment. We respond to several aspects ofthe letter from Ortman and colleagues toclarify points made in our original paper.In Obrycki et al. (2001) we stated that“most corn hybrids already have sub-stantial resistance to corn borers.”We donot believe that this statement meansthat we “claim that traditional plantbreeding has developed corn plants thatadequately protect against European cornborer.”Unfortunately, shooting at a strawman that has very little relation to orig-inal statements is all too common a tac-tic in scientific discourse (Collins andPinch 1998), and it is of particular con-cern regarding an issue as important asthe appropriate use of biotechnology(Shelton and Roush 1999). Corn plantsexpress varying levels of resistance at dif-ferent life stages, a fact that plays a vitalrole in the management of corn borers.In addition, modern corn hybrids haverelatively high levels of tolerance to cornborer feeding. The combination of par-tial resistance and tolerance in moderncorn hybrids contrasts with “the nearlycomplete protection provided by Btcorn.” Is complete protection—virtually100% mortality of corn borers—a goal ofecologically based pest management? Human-derived selective forces havebeen identified as one of the most im-portant evolutionary factors on the planet(Palumbi 2001). Recently, the molecu-lar bases of two different Bt resistancemechanisms were identified (Gahan et al.2001, Griffitts et al. 2001). Planting ap-proximately 25% of the corn in theUnited States with Bt corn that causes al-most 100% mortality of corn borers doesnot appear to be a wise use of thisbiotechnology from either an ecologi-cally based approach for population man-agement or an evolutionary perspectiverelative to maintaining suseceptible geno-types of the pest.Ortman and colleagues state that theuse of Bt corn over the last 5 years has re-duced the level of insecticide use. This ispuzzling, because Carpenter and Gianessi(2001) state that “attributing any ob-served changes in insecticide since 1995to the introduction of Bt corn is neces-sarily problematic for several reasons.”One difficulty in demonstrating any dif-ference in insecticide use is that the levelof insecticide use before the introduc-tion of Bt corn was minimal (Rice andOstlie 1997, Wintersteen and Hartzler1997, Carpenter and Gianessi 2001). Forexample, from 1995 to 1998, 1%–2% ofthe corn grown in Iowa was treated withinsecticides for corn borer infestations. IfBt corn is replacing insecticides, we mightexpect 2% of the corn to be planted totransgenic Bt corn. Furthermore, Ortmanand colleagues cite data that indicate only26% of growers who planted Bt corn in1998 actually used less insecticide to con-trol the European corn borer (Hellmichet al. 2000).As stated by Rice and Pilcher (1998),the economic benefits of this technol-ogy will vary with a number of factors re-lated to levels of corn borer infestations,value of field corn, and cost of trans-genic Bt seed. Ortman and colleaguescited the following from the NationalCenter for Food and Agricultural PolicyWeb site (Carpenter and Gianessi 2001):In “10 of the 13 years between 1986 and1998, European corn borer infesta-tions...were such that corn growers wouldhave realized a gain from planting Btcorn.”Extracting this single phrase out ofcontext presents several potential mis-conceptions. If data for 1999 are added,then some farmers would have made aprofit in 10 of 14 years.We emphasize theword “some,” because even in years withrelatively high European corn borer lev-els, many fields will not exceed econom-ically damaging levels. Recent evalua-tions of Bt transgenic corn have notdemonstrated consistent economic ben-efits (Hyde et al. 1999,Archer et al. 2000).We believe that the data collected over 2years in replicated field studies undernatural infestations of corn borers (Rice1998, Farnham and Pilcher 1998), as citedin our paper, are some of the best data toevaluate the performance of transgenic Btcorn hybrids in comparison with non-transgenic lines. Carpenter and Gianessi at Iowa State University on October 20, 2014http://bioscience.oxfordjournals.org/Downloaded from 

Transgenic Insecticidal Corn: The Agronomic and Ecological Rationale for Its Use

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Transgenic Insecticidal Corn: The Agronomic and Ecological Rationale for Its Use

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