Bt Crops

Paul JepsonIntegrated Plant Protection

Center

Oregon State University

Examples of traits and their associated Examples of traits and their associated genetic elements and sourcesgenetic elements and sources

TraitTrait Genetic Genetic ElementElement

Gene SourceGene Source

Insect Insect resistanceresistance

Cry1Ab delta-Cry1Ab delta-endotoxinendotoxin

Cry1Ac delta-Cry1Ac delta-endotoxinendotoxin

Cry3A delta-endotoxinCry3A delta-endotoxin

Cry9c delta-endotoxinCry9c delta-endotoxin

Protease inhibitorProtease inhibitor

Bacillus thuringiensisBacillus thuringiensis subsp. subsp. kurstakikurstaki

B. thuringiensisB. thuringiensis subsp. subsp. kurstakikurstaki

B. thuringiensisB. thuringiensis subsp. subsp. TenebrionisTenebrionis

B. thuiringiensisB. thuiringiensis subsp. subsp. TolworthiTolworthi

S. tubersosumS. tubersosum

Source: AgBiosafety, UNL (08/2001)Source: AgBiosafety, UNL (08/2001)

www.agbiosafety.unl.edu

Regulatory approvals for Regulatory approvals for BtBt transgenic transgenic cropscrops

ArgArg AusAustt

CanCan ChiChi JapJap MexMex S.AfS.Afrr

USAUSA EUEU NetNethh

SwiSwi UKUK

Cotton Cotton

EnvirEnvir

FoodFood

FeedFeed

MaizeMaize

EnvirEnvir

FoodFood

FeedFeed

PotatoPotato

EnvirEnvir

FoodFood

FeedFeed

9898

9898

9898

96/8/0196/8/01

98/0198/01

98/0198/01

9696

9696

9696

00/100/1

0101

9696

9696

96/796/7

95/795/7

96/796/7

95/7/95/7/99

95/6/95/6/99

95/7/95/7/99

9797

9797

9797

97/897/8

97/897/8

97/897/8

96/996/9

96/996/9

9696

9797

9797

9797

9797

9797

9797

9797

95/795/7

95/895/8

95/895/8

95/7/95/7/88

95/6/95/6/77

96/7/96/7/88

95/6/95/6/99

94/6/94/6/88

94/6/94/6/88

97/897/8

97/897/8

97/897/89797

979797/897/8

97/897/8 97/897/8

Source: AgBiosafety, UNL (08/2001)

www.agbiosafety.unl.edu

Areas of concern in the public domainAreas of concern in the public domain

• EnvironmentEnvironment• Health• Consumer rights and labeling• Ethics• Concerns targeted to the poor and

excluded• Sustainable vs “industrial”

agricultureSource: Conway, G. Source: Conway, G. (2000) Rockerfeller (2000) Rockerfeller FoundationFoundation

GMO Environmental Risks GMO Environmental Risks and Benefitsand Benefits

• Risks of invasivenessRisks of invasiveness• Non-target organism impactsNon-target organism impacts• New viral diseasesNew viral diseases• Reduced pesticide environmental impactReduced pesticide environmental impact• Reduced rate of land conversionReduced rate of land conversion• Soil conservationSoil conservation• PhytoremediationPhytoremediation

Source: Wolfenbarger & Phifer (2000) Science

Risk of invasivenessRisk of invasivenessSteps that may lead to environmental harmSteps that may lead to environmental harm

Introduction of plantIntroduction of plantSurvival outside Survival outside cultivationcultivation

Pollen flow to wild Pollen flow to wild relativesrelatives

Hybrid formationHybrid formation

Reproduction outside Reproduction outside cultivationcultivation

Hybrid survivalHybrid survival

Hybrid ReproductionHybrid Reproduction

Self-sustaining Self-sustaining populationspopulations

Introgression of gene Introgression of gene into wild relativesinto wild relatives

Spread and persistenceSpread and persistence

Economic of environmental harmEconomic of environmental harm

Source: Wolfenbarger & Phifer (2000) Science

Example of this pathway for Canola

Investigations of risk of invasivenessInvestigations of risk of invasiveness

CropCropPollen flow Pollen flow

to to relativrelativeses

Hybrid Hybrid formatioformationn

Hybrid Hybrid survivalsurvival

Hybrid Hybrid reproductireproductionon

IntrogressiIntrogression to on to relativesrelatives

B. napusB. napus

Herbicide Herbicide toleranttolerant

Gene flow possible

Hybrid formation possible

B. napusB. napus herbicide herbicide tolerant tolerant and fertlity and fertlity restorerrestorer

Hybrid reproduction possible

B. napusB. napus herbicide herbicide toleranttolerant

Pollination of B. campestris, not with S. arvensis

campestris hybrid formed

Hybrid survives

Hybrid reproduces

B. napusB. napus altered oilsaltered oils

B. rapa hybrid germinates

Hybrid survival

Source: Wolfenbarger & Phifer (2000), Science

?

?

?

?

Nature Biotechnology, 2004 22: 642 Nature Biotechnology, 2004 22: 642

O. sativa-weedy rice hybrids containing herbicide resistant traits

O. sativa-weedy rice hybrids containing herbicide resistant traits

Chen, LJ et al 2004, Annals of Botany 93, 67-73

O. sativaO. sativa O. rufipogonO. rufipogon

Design ADesign A Design BDesign B

Design CDesign C

Gene flow frequencies from rice to O. rufipogon varied

between 3% - 8%, measured by SSR markers

Gene flow frequencies from rice to O. rufipogon varied

between 3% - 8%, measured by SSR markers

Bao-Rong Lu

Non-target data considered in latest Non-target data considered in latest EPA risk assessment for EPA risk assessment for BtBt crops* crops*

• Larval and adult honeybeeLarval and adult honeybee• Green lacewingGreen lacewing**• Ladybird beetlesLadybird beetles• Parasitic HymenopteraParasitic Hymenoptera• Monarch butterflyMonarch butterfly**• Avian oral toxicityAvian oral toxicity• Static renewal acute toxicity, Static renewal acute toxicity, DaphniaDaphnia• Corn as food for farmed fishCorn as food for farmed fish• CollembolaCollembola• EarthwormsEarthworms

*Standard studies based on EPA Subdivision M and/or OPPTS 885 Guidelines

OVERALL

Very limited evidence for toxic effects*

Example of an EPA regulatory actionExample of an EPA regulatory action

• October 15October 15thth, 2001 , 2001 ‘Biopesticides ‘Biopesticides Registration Action Document’Registration Action Document’, , USEPA OPPUSEPA OPP

• B.t.B.t. Corn and Corn and B.t.B.t. Cotton Cotton• Extended registrations with Extended registrations with

additional terms and conditionsadditional terms and conditions– Non-target insects: Non-target insects: field census data field census data

requiredrequired– Monarch long-term exposure to Cry 1 Monarch long-term exposure to Cry 1

AbAb– Chronic avian studyChronic avian study

Monarch butterflyMonarch butterfly

Risk assessment over a large geographic Risk assessment over a large geographic scalescale

Monarch butterfly Monarch butterfly researchresearch

• Published in PNAS, 2001Published in PNAS, 2001• Research addressedResearch addressed

– Sensitivity to Sensitivity to B.t.B.t. protein and pollen in the lab protein and pollen in the lab– Pollen burden on milkweed in and near corn Pollen burden on milkweed in and near corn – Exposure assessmentExposure assessment– Effects in the fieldEffects in the field– Overall risk assessmentOverall risk assessment

• Corn used more extensively as a habitat by Monarch Corn used more extensively as a habitat by Monarch butterfly than expectedbutterfly than expected

• Risks to butterflies of most Risks to butterflies of most B.t.B.t. corn events low corn events low• The most toxic event removed from the market-placeThe most toxic event removed from the market-place

Impacts of Impacts of conventionalconventional pesticides on pesticides on field boundary Lepidopterafield boundary Lepidoptera

•Spray drifts Spray drifts onto field onto field boundary boundary vegetationvegetation

•Low Low pyrethroid pyrethroid doses have doses have an anti-an anti-feedant feedant effecteffect

•Pupae are Pupae are reduced in reduced in sizesize

•Adults Adults are are smallersmaller(Cilgi and (Cilgi and Jepson, 1995)Jepson, 1995)

Butterfly mortality can occur as a result of Butterfly mortality can occur as a result of pesticide drift into field boundariespesticide drift into field boundaries

Longley et al, ’97, Env. Tox. & Chem., 16, 165-172

e.g. mortality of e.g. mortality of Pieridae in Pieridae in boundaries boundaries exposed to exposed to pyrethroid driftpyrethroid drift

Field census data:Field census data: Natural Enemy Abundance in Natural Enemy Abundance in B.t. and Conventional Cotton B.t. and Conventional Cotton

FieldsFields

Head, G., Freeman, B.,Head, G., Freeman, B.,

Moar, W., Ruberson J., Moar, W., Ruberson J.,

And Turnipseed, S.And Turnipseed, S.

Spiders in Cotton FieldsSpiders in Cotton Fields

0

10

20

30

40

50

60

20-Jun 27-Jun 04-Jul 11-Jul 18-Jul 25-Jul 02-Aug

Date

Ab

un

dan

ce /

sam

ple

Ab

un

dan

ce /

sam

ple

Conventional

Bt cotton

Source, Head et al

Ladybird Beetles in Cotton FieldsLadybird Beetles in Cotton Fields

0

20

40

60

80

100

120

140

20-Jun 27-Jun 04-Jul 11-Jul 18-Jul 25-Jul 02-Aug

Date

Ab

un

dan

ce /

sam

ple

Ab

un

dan

ce /

sam

ple

Conventional

Bt cotton

Source, Head et al

Farm-scale effects of using genetically Farm-scale effects of using genetically engineered crops engineered crops

YIELDYIELD NET NET RETURNSRETURNS

PESTICIDE PESTICIDE USEUSE

Herbicide Herbicide tolerant tolerant cottoncotton

++ ++ 00

Herbicide Herbicide tolerant tolerant soybeanssoybeans

++ 00 --

B.t.B.t. cotton cotton ++ ++ --Source, Fernandez-Cornejo,J., McBride, W.D. (2000) USDA ERS

Some beneficial invertebrates are locally extirpated by repeated application of conventional pesticides to whole fields

e.g. Carabid ground beetles

., 30, 696-705•These effects are not detected in short term, within-field experimental regimes

•They have been seen repeatedly in large-scale multi-field experiments

Evidence for scale-dependency in ecological impactsEvidence for scale-dependency in ecological impacts

Many non-target species disperse within and between fields Many non-target species disperse within and between fields and repopulate areas following reductions after pesticide and repopulate areas following reductions after pesticide

useuse

ground spiders

rove beetles

ground beetles

lacewings

parasitoid wasps

predacious bugs

ballooning spiders

hoverflies

ladybird beetles

~ Short Range ~ Long Range~ Middle Range

Transgenic Transgenic vs.vs. conventional conventional deliverydelivery

Indirect effects may be more important than direct effects– Specialist natural enemies may be reduced

because of profound impacts on target herbivores in all B.t. fields

Exposure pathways very different– Most non-target taxa are not exposed to plant-

incorporated protectants at all: a feeding pathway is required for toxicity

– Certain taxa exposed to PIP’s via diet, for the whole season, and some of these may be susceptible

– Exposure is synchronized between fields

Spider population modelingLandscape average where 50% of fields sprayed in week 24, or in

an increasing range of dates in weeks 20-23, & 25-29 (From Halley et al., 1996, J. Appl. Ecol.)

With short-persistence pesticides, small variation in the range of exposure timings can generate effective refugia

within fields that have been sprayed

Rapid response of spiders to small variation in spray timing is a function of high dispersal and

reproductive rates e.g. (Thomas et al.(2003) J. Appl. Ecol.)

Selection of organisms for monitoringSelection of organisms for monitoring

•Exposure: detritivores, herbivores, predators and parasites

•Indirect effects: trophic position, diet specialization

Conclusions (Part 1)• Environmental risk assessment still under

development, particularly for risk of gene flow, and for large scale effects

• Ability to determine higher risk situations improving

• PIP’s significantly different to pesticides• Benefits of pesticide reductions need to be

examined• Potential use within sustainable development

programs not certain: many other factors are important

• Acceptance of work demonstrating negative impacts has been poor (J. Ag. & Env. Ethics. (2001) 14: 3028)

FIFRA Scientific Advisory Panel Concerns FIFRA Scientific Advisory Panel Concerns about data submitted by industryabout data submitted by industry

• Many ‘tier 1’ tests submitted by industry are flawed or incomplete

– Presence of toxin not demonstrated in artificial diets for test species– Control mortality so high that it masks possible effects– Some tests (e.g. treated insect eggs), do not expose certain insect

predators to the toxin– No statistical analysis of some tests

• Field evaluation no substitute for tier 1 risk assessment testing• Data do not support EPA statement that Bt corn (MON 863)

results in less impact on non-target invertebrates than conventional pest management practices

• Several field studies had no statistical analysis to support them• Plot sizes were trivial, reducing likelihood of detecting

treatment effects (even highly toxic pesticide effects were nor detectable in some investigations)

• Statistical power halved in GM crop plots as a result of flawed experimental design

Non-target invertebrates: Recommendations: Specific Recommendations: Specific

(Made in consultation with USDA APHIS, 2003)• Develop database of approved protocols Develop database of approved protocols

– Exposure and its validation– Species selection and source– Test protocols– Statistical approaches– GLP QA standards including criteria for non-acceptability

• Adopt a policy of exploiting the range of internationally available test Adopt a policy of exploiting the range of internationally available test methodsmethods– Participate in international working groups (SETAC, IOBC, ISO, OECD)

• Develop decision process for test selectionDevelop decision process for test selection– Relevant, but narrow range of options– Representativeness of taxon– Taxa that fall within susceptibility range

• Develop a database of resultsDevelop a database of results• Develop clear criteria for test evaluationDevelop clear criteria for test evaluation

– E.g. for field tests, standards for design, layout, sampling method, taxonomic resolution, E.g. for field tests, standards for design, layout, sampling method, taxonomic resolution, statistics etcstatistics etc

• Adhere to the principles of tier-wise testingAdhere to the principles of tier-wise testing– Triggers between stages– Understand role and limitations of laboratory tests– Exploit semi-field, field, and monitoring studies

• Initiate development of geographically explicit risk assessmentInitiate development of geographically explicit risk assessment– Zones of risk

Use of Environmental Impact Quotients to compare pesticide

environmental risks in conventional and transgenic

cotton

Traditional cotton (853 fields)

B.t. cotton (1032 fields)

Mean S.E.

Range Mean S.E.

Range

AI (kg/ha) 4.10 0.01

0-13.4 2.38 0.06

0-25.1

Formulated pesticide(kg/ha)

15.57 0.26

0-78.4 8.58 0.19

0-55.0

Traditional cotton (853 fields)

B.t. cotton (1032 fields)

Mean S.E.

Range Mean S.E.

Range

Number sprays/crop

11.04 0.12

1-27 6.62 0.11

1-17

Mass application rates and spray frequencies in B.t. and traditional cotton

Average Pesticide Use/Grower (Kg/ha)

0.0

87.5

175.0

262.5

350.0

0.0 7.5 15.0 22.5 30.0

Histogram of SumOfAI_Kg_Ha

SumOfAI_Kg_Ha

Count

0.0

30.0

60.0

90.0

120.0

0.0 3.5 7.0 10.5 14.0

Histogram of SumOfAI_Kg_Ha

SumOfAI_Kg_Ha

Count

Bt-Cotton Traditional Cotton

Most commodities world-wide are treated with <1 Kg/Ha/year

Average Number of Sprays/Grower

0.0

30.0

60.0

90.0

120.0

0.0 5.0 10.0 15.0 20.0

Histogram of Sprays_Grower

Sprays_Grower

Cou

nt

0.0

62.5

125.0

187.5

250.0

0.0 7.5 15.0 22.5 30.0

Histogram of Sprays_Grower

Sprays_Grower

Count

Bt-Cotton Traditional Cotton

A method to measure pesticide environmental impact

• Rating system used to develop environmental impact quotient (EIQ, Kovach et al., 1992) (1, least toxic, 5, most harmful)

• Mode of action: non-systemic (1), all herbicides (1), systemic (3)• Acute dermal LD50 for rabbits/rats (mg/kg): >2000 (1), 200-2000

(3), <1-200 (5)• Long-term health effects: little or none (1), possible (3), definite (5)• Plant surface residue half-life: 1-2 weeks (1), 2-4 weeks (3), >4

weeks (5)• Soil residue half life: <30 d (1), 30-100 d (3), >100 d (5)• Toxicity to fish (96h LC50): >10 ppm (1), 1-10 ppm (3), <1 ppm (5)• Toxicity to birds (8-day LC50): >1000ppm (1), 100-1000 ppm (3), 1-

100 ppm (5)• Toxicity to bees: rel. non-toxic (1), mod. toxic (3), highly toxic (5)• Toxicity to beneficials: low impact (1), moderate impact (3) severe

impact (5)• Groundwater and run-off potential: small (1), medium (3), large (5)

Calculating the EIQ

• EIQ = [C[(DT*5)+(DT*P)]+[C*((S+P)/2*SY)+(L)]+[(F*R)+(D*((S+P)/2)*3)+(Z*P*3)+(B*P*5)]}/3

• DT= dermal toxicity, C= chronic toxicity, SY=systemicity, F= fish toxicity, L=leaching potential, R= surface loss potential, D=bird toxicity, S= soil half

life, Z=bee toxicity, B=beneficial arthropod toxicity, P=plant surface half life

• EIQ (field use rating)= EIQ *%AI*rate

Quotient Traditional cotton (853 fields)

Bt cotton (1032 fields)

Mean S.E. Range Mean S.E. Range

Field EIQ 199.2 3.87 0-723.7 106.2 2.51 0-478.2

Farm worker 191.0 3.87 0-747.0 101.3 2.44 0-438.1

Consumer 29.5 0.58 0-112.1 15.8 0.37 0-69.3

Ecological 377.1 7.31 0-1374.3 201.6 4.81 0-1124.5

Aquatic/fish 92.2 1.90 0-329.4 45.0 1.22 0-322.7

Bird 108.6 2.40 0-475.6 57.4 1.54 0-312.1

Bee 62.3 1.21 0-219.2 35.4 0.84 0-333.6

Predator 114.1 2.10 0-385.0 63.6 1.46 0-368.5

Ground water 8.0 0.15 0-27.3 4.28 0.01 0-23.5

Terrestrial 284.9 5.46 0-1045.0 156.6 3.64 0-801.8

Picker 32.1 0.65 0-128.3 18.5 0.46 0-100.0

Applicator 137.9 2.90 0-564.9 71.7 1.81 0-343.0

Environmental impact quotient, based on Kovach et al. (1992)

Field Use EIQ

0.0

50.0

100.0

150.0

200.0

0.0 125.0 250.0 375.0 500.0

Histogram of SumOfField_Use_EIQ

SumOfField_Use_EIQ

Count

Bt-Cotton

0.0

35.0

70.0

105.0

140.0

0.0 200.0 400.0 600.0 800.0

Histogram of SumOfField_Use_EIQ1

SumOfField_Use_EIQ1

Coun

t

Traditional Cotton

Surface reflectance: Global Surface reflectance: Global Vegetation Monitoring Unit, Vegetation Monitoring Unit,

JRC, IspraJRC, Ispra

Farming systems, FAO/World BankFarming systems, FAO/World Bank

The sensitivity of different farming systems to disturbance highly variable

Conclusions/questions

• At what stage will we know enough to possibly reduce the requirement for extensive testing of Bt crops?

• Are we exhibiting dual standards by requiring greater scrutiny of Bt crops, compared with conventional pesticides?

• Is equivalent scrutiny required at each new location for GM crop adoption?