Insect Resistance Management - CropLife International · including biotech, chemical, biological...

Practical Approaches to InsectResistance Management for

Biotech-Derived Crops

Practical Approaches to Insect Resistance Managementfor Biotech-Derived Crops

Table of Contents

ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

ABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

TERMINOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

1. EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52.1. Stewardship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52.2. Insect protected biotech-derived crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52.3. Insect resistance management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

3. DEVELOPING A ROBUST IRM PLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63.1. Biology and ecology of major pests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63.2. Product deployment strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

3.2.1. Pyramiding versus single insecticidal traits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83.2.2. Local cropping systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103.2.3. Planting choices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103.2.4. Alternative pest management options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

4. INSECT RESISTANCE MANAGEMENT TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124.1. Structured refuges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124.2. Scouting and applying insecticides as needed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124.3. Limiting the use of multiple crops with the same insect control proteins . . . . . . . . . . . . . . . . .124.4. Capping sales to limit market penetration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124.5. Cultivation and destruction of crop residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134.6. Variety resistance and good crop management practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134.7. Using multiple traits targeting the same pests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

5. BASELINE SUSCEPTIBILITY AND MONITORING DAMAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

6. INTEGRATED PEST MANAGEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

7. ENGAGEMENT, EDUCATION AND COMMUNICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

8. EXAMPLES OF IRM PLANS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198.1. Case study: Indian IRM requirements for insect protected cotton . . . . . . . . . . . . . . . . . . . . . .21

9. IMPLEMENTING STRUCTURED REFUGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229.1. Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229.2. Seed distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .239.3. Grower education and communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .239.4. Refuge management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

9.4.1. Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .249.4.2. Planting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259.4.3. Recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

9.5 Monitoring the implementation of refuges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .269.6. Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

10. REMEDIAL ACTION PLANS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

11. DISCUSSION AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

12. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

Appendix 1. SUMMARY OF KEY POINTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

Appendix 2. RECORD OF REFUGE PLANTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

Appendix 3. RECORD OF MONITORING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Appendix 4. EXAMPLES OF IRM LOCAL AND REGIONAL PROGRAMMES . . . . . . . . . . . . . . . . . . . . . . . .35

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Acknowledgements

This training manual was developed from the paper Managing the Risk of Insect Resistance to TransgenicInsect Control Traits: Practical Approaches in Local Environments written by Susan C. MacIntosh, MacIntosh& Associates, Incorporated, 1203 Hartford Avenue, Saint Paul, MN 55116-1622 for CropLife International.Additional information was obtained from academics and the slide set How to Develop an Insect ResistanceManagement Plan: Practical Approaches for Local Environments developed by the Insect Resistance ActionCommittee of CropLife International. The Insect Resistance Action Committee (IRAC) is supported by themember companies of the IRAC Plant Biotechnology Working Group: Bayer CropScience, Dow AgroSciencesLLC, E.I. Dupont De Nemours and Company, Monsanto Company and Syngenta Plant Sciences.

Abbreviations

ABSTC Agriculture Biotechnology Stewardship Technical CommitteeBt Bacillus thuringiensisCICR Central Institute of Cotton ResearchGEAC Genetic Engineering Approval CommitteeIRM Insect Resistance ManagementIRAC Insect Resistance Action CommitteeIPM Integrated Pest Management OECD Organisation for Economic Co-operation and DevelopmentQC/QA Quality Control and Quality AssuranceUS-EPA United States Environmental Protection Agency

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Terminology

Biotech-derived: refers to crops improved through molecular biology techniques that alter the crop genetics.

Bt: is an insecticidal protein obtained from the bacterium, Bacillus thuringiensis, or Bt. It is a commonlyused source of insect protection in biotech-derived crops.

Diapause: refers to a period of inactivity or rest in response to adverse environmental conditions, especiallywinter, during which insect development is suspended.

Grower: refers to a farmer who purchases insect protected, biotech-derived planting material.

Grower agreement: refers to an agreement between the grower and the technology provider that is establishedat purchase of the planting material and which may stipulate insect resistance management requirements forthe particular crop-trait combination and growing area among other stewardship practices.

Growing area: refers to the region where the crop is grown. Insect resistance management requirements mayvary depending on factors present in various growing areas.

High dose: refers to trait-insect combinations where the trait is sufficiently effective, and the target insectpest sufficiently sensitive, so that very few if any of the exposed target pest insects survive. It has beendefined as the dose necessary to control target insects that are heterozygous for resistance alleles.

Insect protected: refers to crops that have been developed to withstand damage from specific insect pests.

IRM: refers to insect resistance management and details the measures taken to delay the development ofresistance to pest control measures in target pest populations.

Key target pests: refers to those pests in a cropping system, that are the most economically damaging and aretargeted by an insect protection trait.

Primary and secondary pests: refers to the dominant pests and the less important pests on a crop, based ontypical population sizes and the levels of crop injury they cause.

Pyramiding genes: refers to a special case of gene stacking where two of more transgenes are combinedin one crop that each provides protection from the same target pest(s) so that there are at least two modesof action.

Refuge: refers to an area of the same crop, or natural vegetation, that does not contain the biotech-derived,insect protection control mechanism.

Refuge calculator: refers to a table of formulas provided to assist growers in the calculation of acceptablerefuge area measurements.

Regulatory authority: refers to any national regulatory authority which might stipulate insect resistancemanagement conditions for the production of specific biotech-derived crops.

Trait: refers to a genetically determined characteristic.

Trait provider: refers to a company or public centre that develops new traits for biotech-derived crops andmakes these available for improved seed.

Transgene: refers to a gene or genetic material that has been transferred by a genetic engineering techniquefrom one organism to another.

Seed distributor: refers to the local company or organisation that distributes seed to growers for cropproduction.

Stacking genes: refers to inserting two or more transgenes into one crop which may be for different traits.

Sustainable agriculture: refers to a combination of farming methods with the common goals of providing morefarm profits, achieving greater environmental stewardship, and benefiting families and communities todaywithout compromising the ability of future generations to meet the same goals.

Threshold levels: refers to levels of pest damage that will affect the yield of the crop. Threshold levels aredetermined for specific pests on specific crops in specific growing areas and are available from extensionofficers and seed suppliers.


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Growers have rapidly adopted biotech-derived cropsthat have been improved to express proteins for insectcontrol, because these crops provide excellentprotection from key damaging insect pests around theworld. Insect protected crops also offer superiorenvironmental and health benefits while increasinggrower income. However, insect resistancedevelopment is an important concern for allstakeholders, including growers, technology providers,and the seed companies that develop biotech-derivedcrops. Given the benefits associated with insectprotected seed, insect resistance management (IRM)must be a consideration when cultivating these crops.It is important that concerns about resistance shouldnot be allowed to prevent the use of biotech crops;rather, these concerns should result in stewardshipand management programmes that effectively delayresistance while enabling the benefits of thetechnology to the environment and to agriculture tobe realised.

The technical data and practical experienceaccumulated by developers, researchers and growerswith insect protected crops in many global regions caninform different aspects of resistance managementleading to robust, science-based IRM plans. A rangeof elements should be considered in assembling anyIRM strategy, including:

• key target pest biology/ecology;

• efficacy of and target pest sensitivity to the insect-protection traits;

• pyramided versus single insecticidal traits;

• product deployment patterns;

• local cropping systems; and

• availability of alternative pest management options,including biotech, chemical, biological and culturalcontrol options.

In addition, insect susceptibility monitoring measuresany changes in pest susceptibility to the insectprotected crop, while stakeholder and growercommunication and education inform the end-usersof any IRM stewardship guidelines and requirements.Infrastructure should be developed such thata remedial action plan can be designed andimplemented should resistance develop. Each of theseelements is described in more detail, with specificexamples of how they can be combined and tailoredto local/regional environments and grower practices.

Insect resistance management plans need to besuitable for the given production situation. What worksfor large monoculture production systems in North andSouth America is unlikely to be appropriate for thesmall, more diverse agriculture of Southeast Asia orAfrica. Although it is clear that insect protected cropsimpart considerable value to growers, it is also clearthat it is in the best interest of all stakeholders topreserve insect protected crops for the long-termbenefits they provide.

1. Executive Summary

2. Introduction

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2.1 STEWARDSHIPStewardship is defined as the responsiblemanagement of a product from its inception throughto its use and ultimate discontinuation (ETS, 2009).In plant biotechnology, stewardship includes theresponsible introduction and use of biotech-derivedproducts across the entire plant product life cycle,from idea, through development and launch, todiscontinuation. Stewardship is a shared responsibilityof the entire value chain including technologydevelopers, seed producers, seed dealers/distributors,grower advisors, growers, and consumers.

Insect resistance management, one of the firstindustry-wide stewardship programmes, wasintroduced in conjunction with the launch of insectprotected, biotech-derived crops in the mid-1990s.For the first generation of insect protected traits (Btcorn and Bt cotton) in the United States, the traits areconsidered to be “high dose” against several keytarget pests and the Environmental Protection Agency(EPA) worked with the technology providers, universityscientists, and grower groups to develop high-dose/refuge-based IRM plans. In developing the IRM plans,it was important to keep the refuge requirementssimple and flexible. For their part, the agriculturalbiotechnology companies agreed to implementcommunication programmes to help growersunderstand the needs and benefits of refuge areas andto implement programmes to monitor adherence.

Local, regional, and international organisations havebeen formed that bring together the trait providers,grower organisations, and academic researchers toaddress scientific issues central to the responsiblestewardship of biotech products in modern agriculture.For example, in the United States the AgricultureBiotechnology Stewardship Technical Committee(ABSTC) is a coalition of biotech companies that playsa key role in the grower-industry interaction on IRM.Similar organisations exist in all countries where Btcrops are commercially cultivated. The InsectResistance Action Committee (IRAC), a specialisttechnical group of the CropLife International industryassociation, has undertaken to provide additionalguidance for the development of IRM plans thataddress these stakeholder concerns.

2.2 INSECT PROTECTED BIOTECH-DERIVED CROPS

An assortment of crops expressing different Bacillusthuringiensis proteins (Bt) has been commercialisedfor insect control and additional products are under

development. Growers have embraced crops (i.e.,maize, cotton, potato and rice) genetically improved toexpress different insect control proteins (i.e., Cry1Ab,Cry1Ac, Cry1F, Cry1A.105, Cry2Ab, mCry3Aa,Cry3Bb, Cry3Aa, Cry34/35, Vip3A), as they provideexcellent protection from key damaging insect pestsin global regions (James, 2008). There is a history ofsafe use of these proteins, both for the environmentand human health (Betz et al., 2000; OECD, 2007;US-EPA, 2001). Recent evaluations have shown thatthese traits provide economic value to adoptingcountries through increased grower income (Brookesand Barfoot, 2006; Gianessi, et al., 2002). Thecontinuing value of this technology can be enhancedthrough appropriate stewardship, such as IRM plans,that can prolong trait efficacy against the target insectpests.

2.3 INSECT RESISTANCEMANAGEMENT

Insect control traits introduced into plants usingmodern biotechnology methods have shown higheconomic value across the globe.

Over the past century, hundreds of insect species havedeveloped resistance to one or more control measures,severely impacting the economics of crop production.Most cases of insect resistance to date involvesynthetic chemical insecticides (Yu, 2008), butresistance has also developed to microbial agents,such as sprayed formulations of Bt (Ferré and VanRie, 2002). The evolution of insect resistance is anongoing concern to crop protection users, includingthose who apply insecticide applications, culturalpractices and host plant resistance.

The goal of resistance management is to delay theevolution of resistance in pest populations exposedto a pest management tool. Resistance can and hasevolved to all forms of pest management, includingchemical, biological, and cultural tools, and is nota unique concern for biotech-derived crops. However,the benefits of biotech-derived insect protection traitsare considered so valuable that the technologyproviders and other stakeholders have placed hugeemphasis on prolonging their durability by slowing therate of resistance development in target pests.Multiple tactics are available to preserve the durabilityof insect management technologies, including usingthe technology only against the most economicallydamaging pest populations, alternating amongdifferent control tactics, or integrating multiple tacticsinto a pest management programme.


3. Developing a robust IRM plan By using a risk management approach, developers andgrowers implement practices that will delay thedevelopment of resistance in insect pests to thesenew crops. This proactive approach of devising andimplementing resistance management strategies willhelp ensure that the new technology is effective formany years so that growers, consumers and theenvironment can benefit from its effectiveness.

Durable, science-based IRM plans have been basedon an extensive array of research data that wascollected before and since the initial introduction ofinsect protected crops. Many important factors, suchas pest biology, pest/crop interactions and resistancegenetics have been investigated. Computer simulationmodels have enabled researchers to evaluate therelative effectiveness of different resistancemanagement options. However, from the beginningit was understood that no matter how detailed theresults, science alone will not result in a robust IRMplan in the absence of practical field experience,information on growing environments and growerpractices.

Insect resistance management plans need to besuitable for the given production situation. Whilepractical experience has accumulated with insectprotected crops in the U.S., Canada, Australia,Argentina, Philippines, South Africa, Spain, and China(Fit, 2003; Wu and Guo, 2005; Matten, et al., 2008),and can inform certain elements of IRM plans, otheraspects must take into account the unique pestpopulation spectrums and distinctive agriculturalpractices found in local growing environments. Forexample, what works for large monoculture productionsystems in North America is unlikely to be appropriatefor the small, more diverse agriculture of SoutheastAsia or Africa.

Uncertainties, such as those inherent in biologicalprocesses and changes in growing environments,trigger a regulatory temptation to be overlyconservative in setting IRM measures, potentially

unnecessarily limiting theuse and availability of

the technology. Bycontrast, there is anatural tendencyfor growers to beless cautious,driven by shortterm needs toproduce a cropin a cost-

effective manner.

Practical IRM needs to strikea balance between thesecompeting perspectives.The goal should be toenable growers to haveaccess to the technology,while providing effectivestewardship that willprovide an acceptable level ofprotection against resistance.

A range of factors needs to be considered whendeveloping an IRM plan for specific crops in specificgrowing areas.

3.1. BIOLOGY AND ECOLOGY OF MAJOR PESTS

The core of the IRM plan is based on the biology ofkey target pests and on pest-crop interaction. Insectresistance management plans developed for differentcountries or regions should be tailored to the specificlocal needs, and while all the elements outlined inthis manual should be considered, some may not belocally appropriate or feasible.

Most crops have a complex of primary and secondarypests. Many secondary pests can be controlled viaother integrated pest management (IPM) tools if thekey target pest is controlled by the trait. The primarytarget pests of the insect protected crop should beidentified for the region and the efficacy of the insectprotected crop characterised for each of these. Theinformation on the biology of the target pest shouldinclude the history of control measures, such asclasses of insecticides sprayed in the area and thecombination of IPM approaches adopted, to assessthe potential for resistance development.

The life cycle of the insect pest, including the numberof generations of the pest in different growing regionsand seasons, annual migrations and the movement ofboth larval and adult stages of each target pest on thecrop and other host plants, should be investigatedwith the help of local entomology and pathologyexperts. The location, timing and distribution offeeding damage on the crop should be understood.If refuge is an aspect of the IRM plan, insectmovement has a direct impact on the design ofa refuge for producing susceptible insects.

For polyphagous pests, that eat many different plantspecies, the availability and suitability of alternativehost plants, such as other crops, natural vegetationand weeds, or a combination of these, can beconsidered as refuge so long as sufficient susceptible

No matter howdetailed the results,science alone will notresult in a robust IRMplan in the absence of

practical field experience,information on growingenvironments andgrower practices.

Insectresistancemanagement

plans need to besuitable for thegiven production

situation.

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insects are reliably produced at the same time and inthe same areas as the Bt crop is grown. This iscommonly referred to as a “natural refuge” and candominate the life system of a target pest species in aparticular release area such that the resistance risk isacceptable. Some examples of generalist andspecialist insect pests are given in Table 1.

3.2. PRODUCT DEPLOYMENT STRATEGIES

Characterisation of the insect protected crop as itrelates to the IRM plan should include theeffectiveness of the trait at protecting the crop andcontrolling the insect pests in different plant partsand across the growing season. This characterisationof the insect protected crop will help identify possiblecontrol gaps where additional control measures mightbe necessary. For example, under heavy insectpressure, it is not unusual for certain types of insectprotected crop to require supplemental insecticidesprays to protect yield. Such sprays are expected toreduce the selection pressure for resistance to theinsect protected crop.

A “high dose” trait-insect combination means that thetrait is sufficiently effective, and the target insect pestsufficiently sensitive to it, that very few if any of theexposed target pest insects survive. In this situation,the “high-dose/refuge” approach may be appropriate,whereby provision of a small refuge, consisting of ahost crop that does not have traits for controlling thepest, allows the production of large numbers ofsusceptible insects. These susceptible insects arethen available to mate with any resistant insectssurviving in the insect protected crop and to passsusceptibility on to the offspring. In some crops, therefuge can be provided as a seed blend of insectprotected and non-insect protected seeds; in others,and more commonly today, the refuge should beplanted separately from the insect protected crop,as a block or as strips within the insect protectedfield, or in a nearby field.

The high-dose/refugeapproach is notalways applicableto all situationsas it relies onhigh sensitivityof the pestpopulation to theinsect protectedcrop and a farminginfrastructure that isamenable to managingstructured refuges. In manysituations, one or more of the target pests is nothighly sensitive. In these cases, while a refuge helpsin reducing selection pressure for resistance, otherconsiderations are also important such as:

• the availability of alternative host plants (includingvarieties of the same crop that do not have insectprotection traits) that provide a natural refuge;

• long-range dispersal of the insect population acrossdifferent cropping regions, and

• the use of supplemental control measures thatprovide additional pest management.

There are multiple techniques to reduce insectselection pressure, incorporating methods based onIPM wherever possible. These include, but are notlimited to:

• the use of refuge;

• scouting and applying insecticides as needed;

• rotating different modes of action;

• restricting the use of a single insect control proteinacross multiple crops that form a natural refugecomplex; or limiting the use of multiple crops withthe same insect control proteins;

Table 1: Examples of generalist and specialist insect pests(developed from Bernays and Minkenberg, 1997).

Generalist pests Plants eatenCotton bollworm, Helicoverpa zea

Old world bollworm, Helicoverpa armigera

Tobacco budworm, Heliothis virescens

Cabbage looper, Trichoplusia ni

Specialist pestsEuropean corn borer, Ostrinia nubilalis Primarily maize

Western corn rootworm, Diabrotica virgifera virgifera

Wide variety of

cultivated and

uncultivated

species

The goalshould be to enablegrowers to have

access to the technology,while providing effectivestewardship that willprovide an acceptablelevel of protectionagainst resistance.


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3. Developing a robust IRM plan

• capping sales to limit market penetration;

• destruction of crop residues;

• using locally adapted crop varieties with nativeresistance; and

• combining multiple traits targeting the same pestswithin a plant.

The best IRM plan will match the available productswith the local environment and pest pressureconditions in an IPM manner.

The ideal level of expression of insect protectionproteins in insect protected crops provides:

• adequate control of the target pest(s) at below theeconomic threshold for damage;

• consistent expression throughout the growingseason to ensure control as pest populationsincrease; and

• control of partially resistant insects.

The level of target pest control willdetermine the amount of non-insectprotected plant refuge needed tosupport sufficient susceptiblepopulations. In some cases, therefuge is a structured refuge,i.e. a planting of the non-insectprotected crop, matched bymaturity level and genetics to theinsect protected crop, planted inclose proximity. The refuge can alsobe unstructured, consisting ofalternative host plants, such as othercrops, natural vegetation and weeds or acombination of these so long as sufficientsusceptible insects are produced.

Alternating insect protected crops with differentmodes of action can be used as part of a resistancemanagement strategy to prevent the survival ofpartially resistant pests that may survive from oneseason to the next. To use this strategy, growers mustalternate the planting of two insect protected cropswith different modes of action (see next section).

3.2.1. Pyramiding versus singleinsecticidal traits

Insect control Bt proteins act through a receptor-mediated mechanism. A change in the receptor has

been the most frequently identified resistancemechanism associated with high levels of resistanceto microbial Bt pesticides (Van Rie et al., 1990; Ferréet al., 1991; Tabashnik, et al., 1996). Pyramiding ofdifferent insect protection proteins into the sameplant controls not only a broader spectrum of insects,but may provide superior IRM properties if the insectprotection proteins act by unique mechanisms ofaction on the same target pest. This improved IRMstrategy (called “pyramiding”) is based on the conceptthat resistance to two different control proteinspresent in the same plant is far less likely to developthan resistance to a single control protein (Roush,1994; Roush, 1997; Gould, 1988). The decrease inlikelihood of resistance development is based on thevery low potential for two random mutations to occurin a single insect pest in one generation. Insects thathave one such mutation giving resistance to one traitare still controlled by the second trait.

Knowing the potential for cross-resistance patternsbetween the proteins is useful. Insecticidal proteins,which bind to different receptors in the insect midgut,such as Cry1 and Cry2 Bt proteins in tobaccobudworm, are examples of such a strategy.

Where pyramiding strategies for insectcontrol traits consist of the simultaneoususe of two insecticidal agents withdifferent modes of action against thesame target pests, these can beused to reduce the development ofinsect resistance. In using thisapproach, knowing the potentialfor cross-resistance patternsbetween the proteins is useful, andseed suppliers of pyramided traits

need to ensure that the IRMrequirements are clearly laid out. Insect

protection proteins found in U.S. maizeevents that were available in 2011 are provided

in Table 2.

Researchers have highlighted the IRM advantages ofpyramiding insect control proteins in the same cropvariety indicating that the refuge size could be greatlyreduced or a natural refuge may be sufficient withoutincreasing the risk of insect resistance (Roush, 1997;Zhao et al., 2005). This has been implemented in theUS for cotton with pyramided insect control traits(US-EPA, 2001) and in South Africa for smallholdercotton production. It is important to note that wherestacked genes target different pests, there is no IRMadvantage and the full refuge requirements are stillneeded.

The practiceof saving a portionof the crop seed

harvest for planting inthe next growing seasoncan have importantnegative impacts on

resistance managementfor insect protected

crops.

Table 2. Available maize traits in the U.S., their spectrum of control, refuge amounts and distances for the Midwest(April 2011). (Adapted from: DiFonzo and Cullen, MSU Field Crops Entomology Program, CDD #288)

Current Bt Protein(s) Insects controlled (bold) Herbicide Refuge %, distanceor suppressed (italics) tolerance in the MIDWESTAbove ground In soil

Agrisure productsAgrisure CB/LL Cry1Ab ECB CEW FAW SB – LL 20% – 1/2 mileAgrisure GT/CB/LL Cry1Ab ECB CEW FAW SB _ GT LL 20% – 1/2 mileAgrisure RW mCry3A – CRW – 20% – adjacentAgrisure GT/RW mCry3A – CRW GT 20% – adjacentAgrisure CB/LL/RW Cry1Ab mCry3A ECB CEW FAW SB CRW LL 20% – adjacentAgrisure 3000GT Cry1Ab mCry3A ECB CEW FAW SB CRW GT LL 20% – adjacentAgrisure Viptera Cry1Ab Vip3A BCW CEW – GT LL 20% – 1/2 mile3110 ECB FAW WBC SBAgrisure Viptera Cry1Ab mCry3A BCW CEW CRW GT LL 20% – adjacent3111 Vip3A ECB FAW WBC SBAgrisure Viptera Cry1Ab Cry1F BCW CEW – GT LL 5% – 1/2 mile3220 Vip3A ECB FAW WBC SB

Herculex productsHerculex 1 (HX1) Cry1F BCW ECB FAW WBC – LL 20% – 1/2 mile

CEW RR2 (some)Herculex RW (HXRW) Cry34/35Ab1 – CRW LL 20% – adjacentHerculex XTRA (HXX) Cry1F BCW ECB FAW WBC CRW LL 20% – adjacent

Cry34/35Ab1 CEW RR2 (some)Optimum products

Optimum Intrasect Cry1F Cry1Ab BCW ECB FAW WBC – LL RR2 5% – 1/2 mileCEW

Optimum AcreMaxRW Cry34/35Ab1 – CRW RR2 10% in the bagOptimum AcreMax1 Cry1F BCW ECB FAW WBC CRW LL RR2 10% in the bag (CRW)(AM1) Cry34/35Ab1 CEW & 20% – 1/2 mile (ECB)

YieldGard productsYGCB Cry1Ab ECB CEW FAW SB – RR2 (some) 20% – 1/2 mileYGRW Cry3Bb1 CRW RR2 (some) 20% – adjacentYieldGard Plus Cry1Ab Cry3Bb1 ECB CEW FAW SB CRW RR2 (some) 20% – adjacentYieldGard VTRW Cry3Bb1 CRW RR2 20% – adjacentYieldGard VT Triple Cry1Ab Cry3Bb1 ECB CEW FAW SB CRW RR2 20% – adjacent

Genuity/SmartStax productsGenuity VT Cry1A.105 CEW ECB FAW – RR2 5% – 1/2 mileDouble Pro (VT2P) Cry2Ab2Genuity VT Cry1A.105 CEW ECB FAW CRW RR2 20% – adjacentTriple Pro (VT3P) Cry2Ab2 Cry3Bb1SmartStax (Dow) or Cry1A.105 BCW CEW CRW LL RR2 5% – adjacentGenuity Smartstax Cry2Ab2 Cry1F ECB FAW WBC (Monsanto) (SSX) Cry3Bb1

Cry34/35Ab1Genuity SSX Same as SSX Same as SSX LL RR2 For 2012RIB Complete (Mon) 5% in the bagREFUGE ADVANCED Same as SSX Same as SSX LL RR2 For 2012Powered by 5% in the bagSSX (Dow)

BCW black cutworm; CEW corn earworm; CRW corn rootworm; ECB European corn borer; FAW fall armyworm; SB stalk borer; WBC western bean cutworm; GT glyphosate tolerant; LL Liberty Link, glufosinate tolerant; RR2 Roundup Ready 2, glyphosate tolerant.

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10

3. Developing a robust IRM plan

3.2.2. Local cropping systemsAgricultural cropping systems vary by crops, countryand culture. High production agriculture may favourcrop monocultures across very large areas with fewwild or uncultivated areas. Other environments maysupport a wide diversity of crops on small plots, orcrops intermixed with wild vegetation within thelandscape. The risk of resistance development isaffected by these patterns, with increased riskoften associated with monoculture croppingand higher market penetration.

The practice of saving a portion of thecrop seed harvest for planting in thenext growing season can haveimportant negative impacts onresistance management for insectprotected crops. The practice wouldundermine IRM efforts by:

• creating a mixture of plants withdifferent genotypes, including some plantswithout genes for insect protection;

• removing quality control and quality assurance(QC/QA) efforts in the production of the seedresulting in variable trait expression;

• limiting the accuracy of market penetrationassessments, if saved seed is not registered whenplanted;

• weakening insect monitoring plans bycircumventing the record keeping of volumes andareas where specific varieties are grown;

• preventing effective grower communication andeducation efforts; and

• separating pyramided traits that were combinedduring crop breeding.

Without proper QC/QA by a professional seedcompany, uniform high dose deployment of the traitand even trait purity can be compromised. If themarket penetration numbers are inaccurate, markettriggers and caps become impractical and insectmonitoring for insect susceptibility will be hamperedbecause the available sampling locations are not allidentified. In order to share critical educationinformation, technology providers, distributors anddealers must be able to identify growers who willbenefit from this information.

3.2.3. Planting choices In some cases, the crop may only be grown duringcertain times of the year, while the pest populationpersists throughout the year, surviving on other hostplants. This can create a temporal refuge whereby

selection for resistance is relaxed, and resistantinsects may be at a fitness disadvantage. In othercases, there may be year-round production of the crop,perhaps with sequential plantings, in which caseselection pressure for resistance may be continuous.

The geographic fit of a particular insect protected cropmay be limited, perhaps only being preferred in areas

of repeatedly high pest pressure; in other areas thepest population may remain at low levels.

Such a situation would reduce population-wide selection pressure for resistance.

Alternating insect protected cropswith different modes of action can beused as part of an IRM strategy toprevent the survival of partiallyresistant pests that may survive fromone season to the next. To use this

strategy, growers must alternate theplanting of two insect protected crops with

different modes of action.

Availability of competing insect protection traits in thecrop against the same pests can also reduce selectionpressure. If different traits are available in one crop orin the market, the selection pressure for resistance toany one is reduced compared with the situation wherea single trait dominates the market. The latter case isthe situation under which IRM plans were firstdeveloped in North America, as at that time onlyCry1Ab was available to control European corn borer(ECB) in corn and only Cry1Ac was available to controltobacco budworm in cotton.

Monitoring the adoption rate of insect protected cropson a regular basis is important for identifying thehighest risk areas. Knowledge of market penetrationtogether with regional market triggers provides usefulrisk management tools for refuge deployment andinsect susceptibility monitoring.

3.2.4. Alternative pest management options

Only rarely will insect-protected biotech productsrepresent the only option for managing a pestpopulation. Usually crop damage by insects ismanaged using a combination of pest managementtools, such as manipulation of planting dates to avoidpeak pest populations at times when the crop isvulnerable. Using native tolerance or resistant cropvarieties can limit the impact of pest populations.Crop rotation is a very effective tool against relativelysedentary pests. Synthetic or biological insecticidesare frequently available to reduce populations beloweconomically damaging levels. Other biotech traitsmay also be available. Use of these alternatives meansthat selection pressures for resistance to a newlyintroduced biotech trait can be much lower than

Withoutproper QC/QA bya professional seedcompany, uniform highdose deployment ofthe trait and eventrait purity can becompromised.

anticipated. Similarly, availability of these tools meansthat pest populations that are evolvingresistance can still be managed, so thatthe impact of resistance on cropproduction can be lower thananticipated.

When pest pressure levels triggerthe need for additional controlmeasures, growers shouldconsult local guidelines andchose a control option, orcombination of treatments, thatcause the least impact onbeneficial organisms. Beneficialorganisms are important componentsin IPM and should be protected as muchas possible.

When selecting chemical control measures growersshould follow the label requirements on the chosen

product and the guidelines for the insect protectedcrop. Importantly, no pest control products

containing Bt should be used on fields thatcontain biotech-derived insectprotected plants with in-plant Btcontrol mechanisms. Some refugesmay not be treated with chemicalcontrols at certain growth stagesof the target organism. Forexample, in some U.S. growingareas, insecticides labelled foradult pest control should not beused in the refuge during theemergence of the adult pests.

In some cases, the crop may have in-plant weed control mechanisms not

present in the refuge, or vice versa. The growerneedsto select appropriate weed control mechanismsfor the crop and the refuge based on the genetics ofthe varieties.

When pestpressure levels

trigger the need foradditional control

measures, growers shouldconsult local guidelines andchose a control option, orcombination of treatments,

that cause the leastimpact on beneficial

organisms.

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12

4. Insect resistance management toolsThere are multiple techniques that can reduce theresistance selection pressure on insect pestpopulations. The best IRM plan will match theavailable products with the local environment andgrowing conditions in an integrated manner.

4.1 Structured refugesRefuges contain crop plants without a biotech trait forprotection against the target insects and provide anarea where susceptible insects can thrive. This areaserves to dilute selection pressure for resistance. Inthe case of a “high dose” trait, the susceptible insectsproduced by the refuge area additionally serve to matewith any rare resistant insects surviving in the insectprotected crop area. This prevents inheritance by theprogeny of resistance to the control protein.

The size of the structured refuge area must take intoaccount the factors that affect the selection pressurefor resistance discussed above, as well as groweracceptance. Refuge areas typically yield less thantheir biotech counterparts because they must sustainsome level of insect damage to produce susceptibleinsects. The value of the crop and the level ofindustrialisation of the agricultural system (versussubsistence farming) must be taken into accountwhen determining appropriate refuge sizes.

In many situations, it is most desirable for the refugeto be planted as a separate block, or in a separatefield from the insect protected crop. This isolationprevents wandering insects from sampling insectprotected and non-insect protected plants therebyreceiving less than the full insecticidal dose. Crossover of insects from protected to refuge crops or viceversa, can reduce the effective refuge size and canfavour the survival of partially-resistant insects. Witha separate refuge, the grower is responsible forensuring the refuge is planted alongside the insectprotected variety. Such a separate refuge can beprovided by supplying a small package of refuge seedalong with the larger amount of biotech-derived seed,or by encouraging the grower to separately purchaserefuge seed.

In other situations, it can be more desirable for therefuge to be provided as a seed blend. This simplifiesthe grower’s operations and shifts the onus ofcompliance with refuge requirements to the seedprovider. In cases where insect movement amongplants is limited, or where the movement doesn’tfavour survival of partially-resistant insects, seedblends may be highly effective.

4.2 Scouting and applying insecticides as needed

No biotech-derived insect protected crop should beregarded as a complete solution to all pest problems.Any trait is only effective against a subset of pestspecies, and the level of control of the target speciesis often imperfect. This means that growers of insectprotected crop varieties must continue to scout theirfields for damaging insect populations and useinsecticides when economic damage thresholds arereached. Application of insecticides to a target pestpopulation will help control any portion of thatpopulation that may be developing resistance to theinsect control proteins in the crop.

4.3 Limiting the use of multiple crops with the same insect control proteins

In situations where a natural refuge is considered animportant factor in reducing selection pressure forresistance and where a large proportion of that naturalrefuge is also a crop, it may be helpful to limit the useof the same or similar insect control proteins in thenatural refuge crop. This could be accomplished bylimiting the areas in which insect protected varieties ofthe second crop are grown, or by requiring the use ofa structured refuge for the refuge crop. This wouldrequire planning that includes an economic and socialanalysis to balance the relative benefits of using insectprotection traits in the different crops. For example, inthe United States, it is recognised that host crops forHelicoverpa zea, such as maize and soybean, representimportant components of the natural refuge for insectprotected cotton. No insect protection traits arecurrently commercially used in soybean, and insectprotected hybrids of maize require a structured refuge.Therefore both conventional corn and soybeans act asrefuge for insect protected cotton.

4.4 Capping sales to limit marketpenetration

As market adoption of insect protection traitsincreases, so does the selection pressure forresistance. One tool to limit selection pressure is tocap sales of insect-protected varieties at some level.Monitoring the adoption rate of insect protected cropson a regular basis is important for identifying thehighest risk areas and monitoring data can be usedto trigger refuge deployment and insect susceptibilitymonitoring. For example, in the Philippines, whena specific market penetration level is reached (i.e.,80%), then all single gene insect protected maizecrops must deploy a structured refuge. Until then,the prevalence of non-insect protected host plants canserve as the refuge.

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Specific market caps can limit the planting of insectprotected crops or favour insect control proteins inone crop but not another as a method of reducingselection pressure. Caps could be applied to specificgeographic regions. However, a decision to implementsuch a cap, and the limits placed on planting wouldhave to take into account the economic and socialimplications of restricting availability of a beneficialcrop protection tool. It can also be logisticallycomplex to enforce such a cap. For example, a marketcap of 30% was put in place for the first insectprotected cotton grown in Australia, which containeda single Cry protein. In addition, the growers wererequired to:

• plant refuge;

• avoid late planting to prevent high pest pressure;

• cultivate to destroy pupae in crop residue;

• work within defined spray thresholds; and

• monitor moth populations for resistance to the Cryprotein (Davidson, 2003).

The subsequent introduction of biotech-derived cottonwith two different insect control genes for the targetedpests helped to reduce these IRM requirements.

4.5 Cultivation and destruction ofcrop residues

For insects that over-winter in the soil, tillage canreduce survival of any resistant insects by exposingthem to adverse environmental conditions, resulting inmortality through natural processes such desiccation,freezing, or over-heating. “Pupae busting” withcultivation is a central component of the insectprotected cotton resistance management programmein Australia.

For insects that over-winter within crop residues, suchas corn borers that diapause as larvae inside tunnelsat the bottom of corn stalks, destruction of the cropresidues after harvest will kill large numbers of thesepests. This action serves to reduce pest presence inthe following growing cycle. Destruction of cropresidues can also be effective for insects that feedwithin the harvested portion of the crop, such as infresh produce fruits and potato tubers. In some cases,harvesting the insect protected crop before insectscomplete their development will reduce overallsurvival of any resistant insects, while elimination anddestruction of infected harvested material will lowerincidence rate for the pest.

4.6 Variety resistance & good crop management practices

For several reasons, healthy locally adapted crops willprovide resistance management advantages. Locallyadapted varieties often possess native insectresistance or tolerance traits, having evolved or beendeveloped to withstand some level of pest pressure.Healthy crops, produced with good crop managementpractices, will produce the expected levels of theinsect protection proteins, ensuring that the dose andefficacy are matched with the IRM plan. Healthyrefuge crops will produce more susceptible insectsand better yields than inferior varieties or poorlymanaged crops.

4.7 Using multiple traits targeting the same pests

As with any pest control technology, over-reliance ona single mode of action can rapidly lead to resistancedevelopment. As discussed above, pyramiding insecttraits that provide high levels of protection fromspecific pest species are far more robust than aresingle traits. A pyramiding strategy for insect controltraits consists of the simultaneous use of twoinsecticidal agents with different modes of action.In using this approach, knowing the potential forcross-resistance patterns between the proteins isuseful. Insecticidal proteins, which bind to differentreceptors in the insect midgut, such as Cry1 and Cry2Bt proteins against tobacco budworm, are examples ofsuch a strategy. Pyramiding of insect control proteinshas reduced refuge requirements in the U.S. forcotton (US-EPA, 2001) and maize (Table 2).

In addition to pyramiding, multiple traits can be usedin a mosaic application, where a patchwork of cropswith different insect protection traits is planted on afarm. This mosaic of different traits will reduceselection pressure for resistance against any onecontrol protein, and help preserve the durability of thetechnology. It can be important therefore thatdevelopment and introduction of new traits isencouraged as part of the IRM programme.

In the U.S., the first insect protected maize andcotton varieties only produced Cry1Ab or Cry1Ac Btproteins (which are closely related) for protection fromcorn borers and other lepidopteran pests. However, insubsequent years, new lepidopteran-protection traitshave been introduced, such as Cry1F, Cry2Ab,Cry1A.105, and Vip3A, which all add to the diversityof modes of action encountered by the target pestsand help extend the durability of these crops.


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5. Baseline susceptibility and monitoring damageInsect monitoring encompasses two basic approaches:monitoring the insects for changes in susceptibility tothe control protein and monitoring fields for signs ofunexpected levels of damage due to a key target pest.

Routine insect monitoring can provide importantinformation about the effectiveness of IRMprogrammes and detect shifts in pest susceptibilitybefore widespread resistance occurs at the field level.This enables implementation of actions to mitigatethe crop damage and manage resistant insect pestpopulations. Possible resistant insect populationsare indicated when insect damage surpasseslevels that are normally expected based on thetrait and the pest population patterns. It may bepossible to contain local or isolated hotspots ofresistance with appropriate mitigation measures.Once widespread field failures occur,due to resistance in the key targetpest, it may be too late torescue or sustain the insectprotection efficacy againstthe resistant species inthe affected region;however, if the cropremains effectiveagainst other primarypests, the overall utilityof the insect protectedtrait may be maintained.

As a first step, measuring thebaseline susceptibility of key targetpest populations to the trait across thegrowing area should be completed prior to widespreadplanting of insect protected crops. Subsequentperiodic monitoring (e.g., annual or biennial,depending on the pest and crop) may be warranted tocompare insect susceptibility to the baseline data orknown susceptible populations. Sampling should focuson regions with highest anticipated risk of resistancedevelopment, i.e., areas with high levels of marketpenetration (adoption) and those areas whereinsecticide treatment of non-insect protected crops ishighest. Insect sampling should be done in areasnearby, but not within or adjacent to the insectprotected crop in order to collect sufficient numbersfor testing and to ensure that the sample collected isrepresentative of the local pest population.

To represent a location, it is recommended that atleast 100 larvae, 100 adults, 50 mated females or50 egg masses are collected, but if populations in thefield are small, one half of these numbers will alsoprovide a valid sample. These collections are used to

establish laboratory populations for testing usingstandardized bioassay techniques, where laboratorycultures are feasible. Tests should be performed onthe earliest lab generation possible (ideally the firstgeneration progeny if collected as larvae or adults, orthe larvae hatching if collected as egg masses). Test

systems should be adapted to thespecies and trait of interest,

and usually consist ofpurified insecticidalproteins overlaid orincorporated intoartificial diet.Endpoints can be takenas mortality, growthinhibition, or moult

inhibition. Bioassays canbe conducted at a set

protein concentration witha known response in susceptible

populations (e.g., a discriminatingconcentration that kills or preventsdevelopment of at least 99% of susceptibleinsects, Marçon et al., 2000), orconcentration-response curves to estimateparameters such as the LC50 (concentrationrequired to cause 50% mortality).

Grower monitoring of fields for damage dueto the key target pests is probably the most

important component of resistance monitoring.Growers are likely to be the first to identify a

relevant change in the level of field efficacy of ainsecticidal trait. Therefore, information should bereadily available for growers so they can report anyfindings of damage in the insect protected crop toseed company or technology provider representatives.Contact information should be provided to distributors,dealers and customers in various forms of productliterature, i.e., grower guides and product labels. Oncea report is made, one-on-one communication with thegrower should be initiated to investigate the source ofthe damage.

Once it is verified that the damage was in a fieldplanted with insect protected crop and a key targetpest was involved, a technical representative shouldvisit the grower to:

• investigate the level of crop damage;

• assist the grower in mitigating the problem topreserve the current season crop; and

• report the results for further follow up, if justified.

Insect monitoringencompasses twobasic approaches:

monitoring the insects forchanges in susceptibility tothe control protein andmonitoring fields for signsof unexpected levels ofdamage due to a key

target pest.

Growermonitoring of fieldsfor damage due to

the key target pests isprobably the mostimportant component

of resistancemonitoring.

15

If further follow up confirms that this is a case ofsuspected resistance, additional investigations shouldbe conducted to confirm the level of sensitivity to theinsect protection protein compared with baselinemeasures. If necessary, remedial actions that are inline with the severity of the incident should beinitiated. These may include reporting to regulatory

authorities, i.e. when reporting is required under theconditions of the regulatory approval for commercialproduction, or providing regulators with safetyinformation in a timely manner. The protocols forthese activities are generally included in companystandard operating procedures and in stewardshipguidelines.


1616

6. Integrated pest managementWhen pest pressure levels trigger the need foradditional control measures, growers should consultlocal integrated pest management (IPM) guidelinesand chose a control option, or combination oftreatments, that cause the least impact on beneficialorganisms. Beneficial organisms are importantcomponents in IPM and should be protected as muchas possible. Biotech-derived insect protectedcrops themselves are known to beextremely benign to non-targetarthropods.

The refuge approach to IRM is wellsuited to sustainable agricultureand complements IPM activities,such as the appropriate use of pestthresholds and sampling to informspray regimes. Cultural and biologicalpest control practices are alsocompatible with IPM and are encouragedto improve the management of biotech-derived crops. However, Bt pesticides should not beused on Bt-containing biotech-derived crops, or onrefuges serving these crops.

When selecting chemical control measures growersshould follow the label requirements on the chosenproduct and the guidelines for the biotech-derivedcrop. Importantly, in addition to not using Bt insectcontrol products on refuges, some refuges may not betreated with chemical controls at certain growth stagesof the target organism. For example, in some U.S.growing areas, insecticides labelled for adult pestcontrol should not be used in the refuge during the

emergence of the adult pests. The reduction ofgeneral pesticide use may increase the potential forthe emergence of secondary pests and an IPMapproach can help to manage these secondary pests.

Infestations of pests not controlled by the in-plantinsect protection in biotech-derived crops are possible

during any growing season. In some cases eventarget pest infestations will rise above

economic thresholds for damage andgrowers will need to apply additionalcontrol measures. Growers areencouraged to use local IPM guidesto identify appropriate monitoringschedules, the pests to bemonitored, critical economicthresholds for damage, and therecommended alternative control

measures. There are IPM checklists toassist growers. These include actions

such as:

• selecting appropriate cultivars for the growing areas;

• using cultural control measures to reduce pestloads;

• using recommended scouting and monitoringprogrammes; and

• when needed, choosing additional control measuresthat will have the least impact on beneficialorganisms.

Bt pesticidesshould not be usedon biotech-derived,

insect protected cropsor on refuges servingthese crops if theycontain in-plantprotection from aBt protein.

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7. Engagement, education and communicationResistance management is the responsibility of allstakeholders. The use of insect protected cropsprovides a novel insect control option for themarketplace. Although it is clear that the availabilityof insect protected crops imparts considerable valueto growers, it is also clear that it is in the best interestof all stakeholders to preserve insect protectionproteins for the long-term benefits they will provide(Gianessi et al, 2002). In fact, the proactive effort forgrower education on the responsible use of insectprotected crops in the U.S., for example, as well asthe speed at which these products have been adopted,has been greater than for any other singleinsecticidal product in history (James,2010).

Adoption of IRM plans for insectprotected crops has beensuccessful to date in part becausethey were developed with broadstakeholder participation. Expertsrepresenting trait providers,academic institutions, regulatoryauthorities, grower and commoditygroups, and other local and regionalsupport groups have played a roleduring the development andmaintenance of IRM strategies.

At commercialisation, growereducation on the properuse of the crops andassociated IRM plans isa key component of howthe product is marketedand sold. In line withbest practices andproduct launch policy, seedcompanies, distributors andgrowers should be informed about correct productuse, including the consequences of resistance

development. For example, grower educationmeetings could be held for purchasers of

the product. Other mechanisms foreducation could include technicalbulletins, product brochures, salesmeetings, articles in tradejournals, presentations by localexperts, and grower guides thataccompany the commercialproduct. All of these can beimplemented in addition to thebag tag that accompanies the

insect protected crop plantingmaterial, and which outlines the

contents of the product and directionsfor use.

Successful resistance management should begin before introduction of insect protected crops through:

The establishment of a local infrastructure of experts who can provide input on key target pestbiology and pest/crop interactions that can help to tailor IRM recommendations;

Evaluation by scientific experts of the available data to determine if additional research is neededto support implementation of an initial IRM plan and to refine the deployment of an IRM strategyas new research data and experience with the technology becomes available;

Provision by grower groups and farm advisor organisations of specific crop production practices;evaluation of how IRM components can be practically implemented; and how information on IRMcan be effectively disseminated;

Provision of technical information from commodity groups and technology developers, to enablethe development of educational materials for stakeholders and users;

While this is the ideal approach, it must be realised that not all situations will meet this model. Forexample, in developing countries, the infrastructure might not exist for widely educating growers oninsect resistance management. In these cases, it will be necessary to explore options for implementation.

3

3

3

3

Resistancemanagement isthe responsibility

of allstakeholders.

It is importantthat growers are

trained through familiarvenues that are relevantto their situation, takinginto account the culture,language, education levels,avenues of access toinformation and how

products areprocured.


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It is important that growers are trained throughfamiliar venues that are relevant to their situation,taking into account the culture, language, educationlevels, avenues of access to information and howproducts are procured. Complex IRM plans thatrequire growers to perform additional tasks beyondtheir normal planting and cultivation activities couldcounter good stewardship, so it is better to keepboth the plan and the message simple and direct forgrowers.

Education programmes for growers should cover thefollowing areas relating to resistance management:

• The characteristics of the trait and how itprovides insect protection;

• Expected efficacy against primary and secondarytarget insects;

• Guidelines for planting, management, and harvestfor optimal productivity, including application offertilisers, weed management, and other IPMtechniques;

• Guidance on scouting for target pest damage andthresholds for insecticide applications or other pestmanagement tools;

• Guidance on how to implement refugerequirements, if applicable;

• Potential consequences of not following best cropmanagement practices, including lost yieldpotential, resistance development, and loss of thetechnology;

• Instructions for communicating with crop advisors,seed dealers and/or technology providers if thereare questions about the product performance ormanagement.

7. Engagement, education and communication

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8. Examples of IRM plansUnited States. The introduction of insect protectedcrops in the United States brought powerful new pestcontrol agents to growers, which are so effective andsafe that the EPA made the unprecedented demandfor resistance management plans prior to marketintroduction. Specifically, these early IRM plans werebased on:

• presence in the plant tissues of a high dose of theinsect control protein;

• the use of refuges with no insect control proteincontrol measures, where susceptible insects couldthrive; and

• the expectation that genes for resistance to theinsect control proteins initially occur only rarely ininsect pest populations.

The first IRM plans in the U.S. required an area ofplants without insect control proteins, a refuge, thatwas close to the insect protected crop so that any rareresistant insects that emerge from the insectprotected fields could easily find and mate withsusceptible insects. In this scenario, the genetics ofresistance is diluted out to keep offspring susceptibleto the control protein expressed in the crop.

In theory, this IRM strategy should delay resistancedevelopment as long as the refuge produces sufficientnumbers of susceptible insects so that matingbetween resistant and susceptible insects issignificantly more likely to occur than mating betweeninsects that both have some resistance.

The refuge requirements set by the US-EPA in 2006for insect protected crops are described in Table 3 formaize and Table 4 for cotton.

Table 3. Refuge requirement for Bt maize set by the US-EPA (US-EPA, 2006)

Trait target Refuge size Deployment Proximity

Corn borer 20% (maize regions) Discrete corn borer refuge Internal or external blocks 50% (cotton regions) within ½ mile or in-field strips

(at least 4 rows wide)

Rootworm 20% Discrete rootworm refuge Internal or external blocks adjacent or in-field strips(at least 4 rows wide)

Corn borer + 20% (maize regions) 2 options: Internal or external blocks Rootworm 50% (cotton regions) 1. Common rootworm/corn adjacent or in-field strips

borer refuge (at least 4 rows wide)

2. Discrete rootworm/corn Separate fields should beborer refuges used within ½ mile

Table 4. Refuge requirement for Bt cotton set by the US-EPA (US-EPA, 2006)

Gene # Region Refuge size Deployment Proximity

Single All 1. 5% external unsprayed 1. At least 50m wide 1. ½ mile (¼ mile preferred)

Dual Arizona, 2. 5% embedded 2. At least 50m wide 2. Embedded in fieldCalifornia, 3. 20% external sprayed 3. N/A 3. 1 mile New Mexico, (½ mile preferred)West Texas

Dual Southeast US Natural refuge – no structured refuge requirement

Single / dual For PBWa only N/A At least one row for Embedded in field– Arizona and every 6 to 10 rows California of Bt cotton

a pink bollworm


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Refuges can be economically practical for growersespecially if chemical insecticide treatments (non-Bt)are allowed in the refuge to protect the yield whileallowing sufficient insects to survive that aresusceptible to the control proteins in the insectprotected crop.

Other elements of these initial IRM plans included:

• annual monitoring of target pests for susceptibilityto the control protein expressed in the crop in areaswith high adoption rates;

• communication and education for growers so thatthey fully understand and carry out resistancemeasures;

• monitoring growers for adherence with the IRMplan (i.e., ensuring that the refuge plots are largeenough and at the appropriate distance from theinsect protected field);

• enforcement of adherence through removal oftechnology from growers found repeatedly out ofcompliance; and

• a remedial action plan should resistance bedetected.

A structured non-insect protected crop refuge providesone source of susceptible insects but it may not bethe only source because many insect pests aregeneralists (Table 1) which feed and develop on avariety of different host plants, e.g., cotton bollworm,Helicoverpa zea; tobacco budworm, Heliothisvirescens; cabbage looper, Trichoplusia ni (Bernaysand Minkenberg, 1997). These pests can develop onother cultivated crops as well as non-crop alternativehosts, such as those in uncultivated areas and weedyfield borders. Other insects are classified asspecialists which feed on only one or a few differentspecies (i.e., European corn borer, Ostrinia nubilalis;western corn rootworm, Diabrotica virgifera virgifera).For the generalists, an alternative host refuge mayproduce equal to or larger quantities of insects thanthe structured non-insect protected crop refuge. TheUS-EPA acknowledged this when they removed theneed for a structured non-insect protected cottonrefuge for biotech-derived cotton varieties withpyramided insect protection genes, relying instead onthe abundance of non-cotton plants to provide anatural refuge for Noctuidae species (US-EPA, 2001).

In other areas of the world, a variety of IRM tacticshave been utilised for insect protected crops takinginto account local cropping practices.

Australia. Australian authorities and growers workedtogether to establish IRM plans with the introductionof single-gene insect control cotton in 1996 bylimiting each grower to a cap of 30% of the totalcotton grown per farm, thereby ensuring a large non-insect protected cotton refuge. This cap was removedwhen pyramided insect protected cotton events(containing more than one different insect protectionprotein) were introduced seven years later. The revisedregulatory requirement reflects the reduced potentialfor resistance development associated with varietiesthat have pyramided control genes. Some othercontinuing elements of the IRM plan in Australiainclude restricted planting times, limited insecticideuse on refuges and required cultivation after harvest(‘pupa-busting’), all in an effort to minimise resistancerisk (Davidson, 2003).

China. Because farm production in China is typicallya mixture of small plots of cotton, maize, soybean,wheat and peanut (<5 ha in total) that serve asnatural hosts for the major pest (old world bollworm(OWB), Helicoverpa armigera), there is no requirementfor a separate structured non-insect protected cottonrefuge for insect protected cotton in China (Wu andGuo, 2005). To date, insect protected maize has notbeen approved in China, thereby limiting selectionpressure on OWB which also feeds on maize.

India. In India1, each bag of insect protected cottonseed includes a second bag containing an additional20% of non-insect protected cottonseed to planta refuge. Information is shared on the properdeployment of the non-insect protected refuge.

Philippines. In the Philippines2 , where farm sizeis also small, adopted IRM requirements for insectprotected maize have based the need for a structuredIRM plan on market penetration, similar to theAustralian plan but with different metrics. Untilgrowers in a region plant above 80% of their maizecrop as hybrids containing an insect protected trait,they are not required to plant non-insect protectedmaize as a refuge for the Asian corn borer, Ostriniafurnacalis.

All the plans described above include either annualinsect susceptibility monitoring and/or routinemonitoring for insect damage and follow up testingif populations of the primary target insects are founddamaging an insect protected crop.

South Africa. The IRM requirements for insectprotected cotton production at commercial level area compulsory 5% refuge of conventional cotton that isnever sprayed. A local study has demonstrated that

1 http://www.cicr.org.in/IRM.html 2 http://www.bic.searca.org/info_kits/btcorn_host.pdf

8. Examples of IRM plans

21

sufficient natural refuge exists in the surroundingvegetation in cotton growing areas (Green et al.,2003). The combination of the 5% refuge and thenatural refuge provides a reduced potential forresistance development to the Cry1Ac protein by thelocal cotton pests: ‘African’ bollworm, Helicoverpaarmigera (Hübner); red bollworm Diparopsis castanea(Hampson); and two spiny bollworm species, Eariasbiplaga (Walker) and E. insulana (Boisduval). Cottonevents with pyramided insect protection genes haverecently been approved in South Africa.

8.1. CASE STUDY: INDIAN IRM REQUIREMENTS FOR INSECT PROTECTED COTTON

The Genetic Engineering Approval Committee (GEAC)is the official body in charge of commercial release oftransgenic crops in India, including strategies forinsect resistance management. This is advocated so asto increase the durability of the technology and reducechances for resistance development. Accordingly,biotech-derived insect protected cotton has to beplanted in the centre of the plot and non-transgeniccotton has to be planted as refuge crop surroundingthe central plot, such that it covers at least five rowsor 20% of the total sown area, whichever is more(Figure 1).

Figure 1. Required refuge planting pattern in India forinsect protected cotton

Mixing insect protected (the crop) and non-insectprotected (refuge) seeds together before planting isnot recommended, because larvae move easily fromone plant to the next. The guidelines indicate that

each pack of insect protected cottonseed, when sold,should also contain, in a separate bag, the requiredquantity of non-transgenic seeds to meet therequirements of planting the refuge crop. The plantinglayout has to be indicated in product literatureincluded in the seed pack. Since the standard packsize of cottonseeds in India is 450 g, each pack ofinsect protected cottonseed sold contains one pouchof 450 g of insect protected cottonseeds and anadditional pouch of 120 g of non-insect protectedcottonseeds. For the few years after insect protectedcotton was first released for commercial cultivation inIndia, the non-insect protected counterpart hybridseeds were used for refuge planting. More recently,the GEAC has allowed the flexibility of anyconventional non-insect protected hybrid to be usedin refuge planting.

However, there is no legal basis for the grower tofollow the requirement of refuge planting andadherence enforcement has been a challenge for seedcompanies. Additionally, it has been suggested by thescientific community that considering the abundant,diverse alternate host availability for the target pestand the cropping patterns followed by Indian growers,the requirement for planting refuge areas may beunnecessary in some parts of India (Singla et al.,2010). The many insect host plants in naturalvegetation and the small cotton field sizes,interspersed with vegetable crops, should ensure thatresistant moths emerging from cotton fields will easilymate with susceptible moths from other crops andnatural vegetation. Structured refuges remainnecessary for areas where P. gossypiella and Eraiasspp. are primary pests.

The requirement for baseline susceptibility datageneration by the applicant prior to commercialrelease of insect protected cotton, followed by regularresistance monitoring after commercial release, hasbeen implemented as a part of the IRM strategy. TheCentral Institute of Cotton Research3 (CICR), India’spremier public cotton research institute, has beenentrusted with the responsibility for the regularmonitoring of insect susceptibility.

Refuge: Non-Bt cotton5 rows or 20%

Crop: Bt cotton

3 http://www.cicr.org.in/


22

9. Implementing structured refugesWhere a separate structured refuge is indicated asbeing important for delaying the development ofresistance, special consideration needs to be given topromote grower implementation and appropriatemanagement of the refuge.

9.1. FLEXIBILITYProviding a choice of appropriate systems is essentialas it enables growers to choose an acceptable systemthat best fits their growing conditions, resources andpreferences. For example, growers with appropriateplanting equipment might prefer to plant strips ofrefuge within the insect protected crop, while othersmay prefer to plant separate blocks of the refuge andinsect protected varieties. Appropriate refugeguidelines or requirements clearly define the plantingconfiguration options and the crop protectiontreatments required for each option.

The refuge can be embedded in the biotech-derivedfields, adjacent to these fields or, in some growingareas, shared between fields for some crops. Refugecan be sprayed or unsprayed, depending on the natureof the biotech-derived crop and the size of the refugearea. In general, refuge that will be sprayed for insectcontrol needs to be larger than unsprayed refuge. Forsome insect protected crops, where the naturalvegetation in the growing area has sufficient hostplants to support a population of target pests, the use

of natural vegetation as refuge has been approved forthese growing environments.

When insect protected crops have combinations ofdifferent protection for different pests, each of thesecontrol measures may need to have its own refuge.For example, maize with two different insectprotection proteins that control European corn borerand corn rootworm, will need to have refugesappropriate for both of these pests. In some instancesit is possible for certain control agents to sharerefuge, based on the biology of the pests, the growingenvironment and the control mechanisms. The sizeand distance of these common refuge areas isdetermined by the traits being served by the sharedrefuge. Grower guides provide planting configurationoptions for specific crops in specific growing areas(Figure 2).

The refuge area should be planted and managed inthe same way as the crop. For example, the refugeand insect protected crops should be planted closein time; planted with varieties that have similarmaturation times; be given the same inputs andmanagement (soil preparation, irrigation, weeding,fertiliser, pesticide treatments, etc.); and be plantedat a similar density. These measures are to ensure thatthe refuge remains as attractive as the crop to localpests throughout the growing season.

Block Block

Perimeter

StripsRoad, pathditch, etc.

Within adjacent field

Adjacent <800m(1/2 mile)

800m option valid insome growing areas only

Common refuge ofnon-biotech corn.Minimum four rowsfor each component

Biotech corn withprotection againsttwo different pests

Within

A. 20% corn refuge option for a cotton growing area

or or 800m optionAdjacent

Figure 2. Examples of refuge configurations allowed for two crops in certain growing areas. (Adapted from industry IRM guidelines.)

23

9.2. SEED DISTRIBUTIONInformation for growers about feasible IRM strategiesand, the legal instruments to enforce IRM systems,can be linked to the procurement of seed for insectprotected varieties (Figure 3).

Figure 3. Example of a seed label that indicates IRMrequirements for purchased seed (NCGA).

Before opening a bag of seed, be sure to read and understandthe stewardship requirements, including applicable refugerequirements for insect resistance management, for thebiotechnology traits expressed in the seed set forth in thetechnology agreement that you sign. By opening and using a bagof seed, you are reaffirming your obligation to comply with thosestewardship requirements.

In the U.S. and Canada growers who purchase orobtain biotech-derived seed are required to signgrower agreements that bind them to the use of one ormore IRM systems during the production of the insectprotected crop. Information on the IRM options for thecrop are distributed with the seed and it is up to thegrowers to choose which system best suits theirgrowing conditions, cultivation practices and

resources. However, legal instruments such as thesemay not be acceptable or effective in more diverse orless industrialised agricultural systems.

9.3. GROWER EDUCATION AND COMMUNICATION

Grower education should cover not just what therefuge requirements are, but why they exist and whythey benefit the grower and the farming community inthe long run. Frequent, localised communication maybe needed to help growers fully understand theirresponsibilities and how refuge requirements orguidelines can be met in their particularcircumstances.

9.4. REFUGE MANAGEMENTIf the chosen IRM strategy includes the planting ofrefuge areas, the layout, the seed needs and the inputrequirements must be fully understood and preparedfor before planting. Similarly, if the IRM strategyrequires insecticide treatment, the treatment scheduleand the availability of the identified pesticides bothneed to be verified before planting. In some cases, thecrop may have in-plant weed control mechanisms notpresent in the refuge, or vice versa. The grower needsto select appropriate weed control mechanisms for thecrop and the refuge based on the genetics of thevarieties.

<1.6km

<1.6km

Biotech cottonwith one insectprotection trait

Refuge of non-biotech cotton

Refuge requirements

May be treated withany insecticides,except Bt products

B. 20 % sprayed cotton refuge option

(1 mile)

(1 mile)


24

9. Implementing structured refuges

HayN

Creekside FarmSummer 2010

R24

50m

Hay

Maize 43Bt1 + Bt2

Maize 87sprayed Maize 87

sprayedMaize 43Bt1 + Bt2

SoybeanRR

1.7 Ha

Maize 43Bt1 + Bt2

2.1 Ha

Maize 43Bt1 + Bt2

2.9 Ha

1.2 Ha 0.9 Ha0.3 Ha

5.1 Ha

Maize 43Bt1 + Bt2

1.8 Ha

building

Hay

9.4.1. PlanningGrowers who chose a refuge option for IRM may wishto map out the planting areas and ensure that thevolume and proximity of the refuge are in compliancewith the growers’ agreement for IRM requirements foreach insect protected variety. Field maps help todefine the planting strategy for each season, as wellas guide the management of the crops and the refugeareas through the growing period and during harvest(Figure 4).

Refuge planning, planting and crop management maybe facilitated if fields and refuge areas are mapped.Refuge areas may have different pesticide applicationrequirements and field maps help ensure that

pesticide applications are applied to the correct fields.Where common refuge areas are allowed for certaininsect protected products, growers should plan thesebefore seed purchase and planting to ensure that theymeet the IRM requirements. If maps are not feasible,other records of where refuge and insect protectedfields are located should be maintained.

Refuge calculators are developed to help determinethe amount of refuge needed for a specific insectprotected product or the amount of communal refugeneeded for two or more insect protected products.Table 5 gives examples of refuge calculators for twodifferent refuge area requirements.

Figure 4. Example of a field map showing the relative positions of insect protected crops and refuge areas.

25

9.4.2. PlantingRefuges for many insect protected crop events entailaccurate planting of specific seed in specific areas ona farm. Growers should plant and manage both therefuge areas and the insect protected crop with thesame protocols to ensure that the plants grow andmature at comparable rates. In some cases, insectprotected plants that are interspersed in a refuge areacan lessen the effectiveness of the IRM strategy andthe productivity of the refuge area. As such, growersshould ensure that planting machinery is cleanedthoroughly prior to planting a refuge area.

Refuge can be planted within or adjacent to the insectprotected crop and must not contain the same insectprotection that is present in the crop. When perimeteror in-field strip refuge is planted, a minimum width ofthe strips may be determined for each crop-trait-environment combination and should be describedin information material that is provided to the grower.When planting strip refuge within the field, therequired volume of refuge seed can be loaded into thespecific hoppers on the planter that will ensureplanting of the required refuge strip width. When therefuge seed is finished, the hoppers can be filled withthe insect protected seed for the rest of the planting.

In some cases refuge areas should be under thecontrol of the same grower who is managing the insectprotected crop, especially if farm or field sizes arelarge. It may be appropriate for a group of growers tocooperate in managing refuge areas across multiplefarms, especially if farm size is small.

9.4.3. RecordingAt planting, the growers are encouraged to record theplacement and dimensions of any refuge with respectto the insect protected crop. The refuge areas shouldreceive the same inputs and management protocolsapplied the insect protected events. To provide arecord of adherence, the grower is encouraged torecord the soil preparation protocols that were usedand all inputs for the crop and the refuge during thegrowing season. In addition, it is useful to record allscouting activities and to document any insectdamage identified in the insect protected crop andin the refuge.

Recording is an important tool for managing thedevelopment of insect resistance in insect protectedcrops, however it can also be time consuming and isnot completed by many growers. In some casesgrowers file the labels on planting material packagingand write the planting date on these. Together with amap of the planting areas, this would provide somerecord of the crops on the farm for that season.

This manual contains examples of forms designed tofacilitate recording of the information that is relevantto insect resistance management. Growers can adaptthese forms to their requirements.

A: For 5% refuge requirement

Examples Your field

Field size (hectares) = 40 120 200 300

Maximum insect-protected hectares:Field size x 0.95 = 38 114 190 285

Minimum 5% refuge hectares: Field size x 0.05 = 2 6 10 15

B: For 20% refuge requirement

Examples Your field

Field size (hectares) = 40 120 200 300

Maximum insect protected hectares:Field size x 0.80 = 32 86 160 240

Minimum 20% refuge hectares:Field size x 0.20 = 8 24 40 60

Table 5. Examples of refuge calculators supplied with grower IRM requirements when biotech-derivedinsect protected seed is purchased.


26

9. Implementing structured refuges

9.5 MONITORING THE IMPLEMENTATION OF REFUGES

It is standard practice for technology developers toassess implementation of the IRM strategiesrecommended for their seed. Some regulatoryauthorities require compliance monitoring andreporting as part of the authorisation conditions forcommercial use of insect protected plants. Mostdevelopers or seed companies work with theircustomer during the growing season, discussing theircrop management programmes, challenges

encountered, and checking forinsect damage. Growers

who have not compliedwith the IRMrequirements forinsect protectedbiotech-derived seedshould be providedwith additionaleducation and

assistance. In some

cases, growers who repeatedly ignore refugerequirements can be denied access to the biotechseed in subsequent seasons.

Information from refuge implementation assessmentsshould be used to refine education programmesaround the need for refuges and how best toimplement them. This information can also be used toreview the IRM requirements themselves to see if theycan be made more flexible or more practical withoutsignificantly compromising their effectiveness.

9.6. REPORTINGGrowers are encouraged to report unexpected insectactivity and damage during the growing season.Contact details for submitting these reports should bepart of the seed package label. The seed provider willdiscuss the damage with the grower and togetherdetermine how best to protect the crop and whatfollow-up actions are needed to investigate andmanage any potential insect resistance developmentin the local pest populations.

It is standardpractice fortechnology

developers to assessimplementation of the

IRM strategiesrecommended for

their seed.

10. Remedial action plans The implementation of a remedial action plan shouldoccur if field resistance to an insect protected crop isconfirmed in a key target pest. Depending on thesituation, remedial action plans could have multiplecomponents, such as planting a structured refuge,applying insecticides or other pest management tools,and/or temporarily halting sales of the affected insectprotected crop in the affected area. The immediateremedial action goals should be to:

• protect the grower’s crop investment;

• characterise the resistant insects to enable thedevelopment of case-specific management options;and

• contain the spread of these insects utilising thebest available control methods.

Furthermore, once it has been determined that thedamage is caused by a targeted insect and that theplants contain the insect protection protein, theinvestigation should move to collection and testing

of the insect population(s) for susceptibility to thebiotech-derived insect protection protein. This testingwill be coordinated by the technology developer andshould be done in the specific area of crop damageand in surrounding regions, to delineate the scope ofresistance and compare the bioassay results to pre-commercial baseline data.

For a worst-case scenario, where insect resistance isconfirmed and appears to be spreading, a long-termremedial action plan should be developed. This mayconsist of the integration of additional pest controltechnologies. Other options for controlling the keytarget pests should be identified for growers,including soil cultivation, insecticide applications anduse of alternative biotech-derived insect control traits.If no effective alternatives are available and theinsect protected crop is no longer providing economiclevels of control of key target pests, sales of varietiesexpressing this insect protection protein could besuspended or restricted in the affected region infuture growing seasons.

27


28

11. Discussion and conclusionsIntegrated pest management is an effective andenvironmentally friendly strategy that relies on anarray of pest control techniques that bring togethergenetic and biological information with cultural andmodern pest management methods for a moresustainable crop production system. As long as cropplants have been grown, growers have embraced awide range of tactics to offset insect damage. Theseinclude low technology mechanisms where fieldworkers manually remove insect pests from cropplants and sophisticated IPM systems that encompassmyriad approaches with insect protected crops beingonly the latest of a multitude of science-inspired tools.Insect resistance management employs many of thevery same principles used in integrated pestmanagement to minimise and manage harmful pestoutbreaks to preserve and to help maintain allpossible pest control strategies.

Safeguarding insect protected crops against insectresistance is not only an important concern forgrowers, but also for the technology providers andseed companies that develop these geneticallyimproved crops. While hundreds of Bt strains havebeen identified (Crickmore, et al., 1998), only a fewso far have found commercial success based onsuccessful integration into target plants andacceptable control levels of important agriculturaltarget pests. Intensive screening for new microbialstrains and their associated insecticidal proteins hasprovided a variety of candidates for croptransformation. In addition, trait providers are nowdeveloping and commercialising pyramided traits thatexpress two or more different proteins against thesame pest to prolong trait durability. An increasedunderstanding of how insect protection proteins workat the molecular level has resulted in customizedproteins with improved efficacy and spectrum ofactivity (Bravo and Soberón, 2008; Soberón, et al.,2007; Walters, et al., 2008). As a result of thesescientific advances, insect protection proteins remainan important insect control resource that should bepreserved for their exceptional effectiveness andsuperior environmental and health benefits.

Should resistance in insect protected crops develop,insect damage would undoubtedly increase, leading toa reduction in crop yield and in the value of the insectcontrol technology. Confirmed resistance would havenegative consequences for the environment andgrowers, which might include product withdrawal fromthe market and expanded use of insecticides for pest

control. However, consequences differ by pest: forkey target pests, resistance would lead to reducedyields, but for secondary pests, the major benefit ofthe technology remains and over-reaction (e.g.,complete product withdrawal) could unnecessarilylead to a complete return to synthetic chemistries, orcould put more selection pressure on remaining pestmanagement practices.

In order to identify the best tactics for a robust IRMstrategy, to extend the durability of insect protectedcrops for a given country or region, the followingelements should be evaluated:

• pest biology and ecology;

• trait efficacy and dose;

• expected product deployment patterns;

• local cropping systems;

• use of insect protected crops within IPMprogrammes;

• insect baseline susceptibility and monitoringoptions;

• stakeholder and grower communication andeducation; and

• a remedial action plan in the event of resistancedevelopment.

Each of these elements must be assessed witha specific focus on the local conditions andagricultural practices that should be considered inthe development of an IRM plan, because no matterhow detailed the scientific information, these localconditions are critical for successful IRMdeployment. Effective stakeholder participation,including experts from technology providers, growerand commodity groups, academia, and government,is another important factor during the developmentand implementation of an IRM strategy. As newinformation is collected from research efforts onpest biology and the genetics of resistance and asmore practical experience accumulates with insectprotected crops in various regions and countries,IRM plans and tactics should be reviewed andrefined to extend the durability of all insect protectedcrops globally.

12. ReferencesBernays EA and Minkenberg OPJM. 1997. Insect herbivores: different reasons for being a generalist.Ecology 7:1157-1169.

Betz FS, Hammond BG and Fuchs RL. 2000. Safety and advantages of Bacillus thuringiensis-protected plants tocontrol insect pests. Reg Toxicol Pharmacol 32:156-173.

Bravo A, and Soberón M. 2008. How to cope with insect resistance to Bt toxins?Trends in Biotechnol 26: 573-579.

Brookes G and Barfoot P. 2006. GM crops: The first ten years – Global socio-economic and environmental impacts. ISAAA Briefs, Brief 36: http://www.isaaa.org/ [accessed 26 March 2009)

Crickmore, N., D.R. Zeigler, J. Feitelson, E. Schnepf, J. Van Rie, D. Lereclus, J. Baum, and D.H. Dean. 1998.Revision of the Nomenclature for the Bacillus thuringiensis Pesticidal Crystal Proteins.Microbiology and Molecular Biology Reviews 62: 807-813.http://www.lifesci.sussex.ac.uk/home/Neil_Crickmore/Bt/intro.html [accessed 9 July 2010]

Davidson, S. 2003. Biotech cotton – a budding field. Ecos 14: 28-31.

ETS. 2009. Guide for Stewardship of Biotechnology-Derived Plant Products. Excellence Through Stewardship.http://www.excellencethroughstewardship.org/facts/documents/Guide%20for%20Stewardship.pdf.Accessed 5 May 2010.

Ferré J, and Van Rie J. 2002. Biochemistry and genetics of insect resistance to Bacillus thuringiensis.Ann Rev Entomol 47:501-533.

Ferré J, Real DM, Van Rie J, Jansens S, and Peferoen M. 1991. Resistance to the Bacillus thuringiensisbioinsecticide in a field population of Plutella xylostella is due to a change in a midgut membrane receptor.Proc Nat Acad Sci, USA 88:5119-5123.

Fit G. 2003. Deployment and impact of transgenic Bt cotton in Australia. In The Economic and EnvironmentalImpacts of AgBiotech: A Global Perspective, ed. Kalaitzandonakes, NG, Springer, New York.

Gianessi LP, Silvers CS, Sankula S and Carpenter JE, 2002. Plant biotechnology: Current and potential impact forimproving pest management in U.S. agriculture. An analysis of 40 case studies. www.ncfap.org/publications.html[accessed 26 March 2009]

Green WM, de Billot MC, Joffe T, van Staden L, Bennett-Nel A, du Toit CLN and van der Westhuizen L. 2003.Indigenous plants and weeds on the Makhathini Flats as refuge hosts to maintain bollworm population susceptibilityto transgenic cotton (Bollgard™). African Entomology 11(1): 21–29.

Gould F. 1988. Sustainability of transgenic insecticidal cultivars: Integrating pest genetics and ecology.Ann Rev Entomol 43:701-726.

James, C. (2010). Global Status of Commercialised Biotech/GM Crops: 2010.ISAAA Brief No. 42. ISAAA: Ithaca, NY.

Marçon PCRG, Siegried BD, Spencer T, and Hutchinson WD. 2000. Development of a diagnostic concentrations formonitoring Bacillus thuringiensis resistance in European Corn Borer (Lepidoptera: Crambidae).J Econ Entomol 93:925-930.

Matten SR, Head GP and Quemada HD. 2008 How governmental regulation can help or hinder the integration of Bt crops within IPM programmes, in Integration of insect-resistant GM crops within IPM Programmes. eds. RomeisJ, Shelton AM and Kennedy GG, Springer, New York.

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OECD. 2007. Consensus document on safety information on transgenic plants expressing Bacillus thuringiensis-derived insect control protein. Organization for Economic Co-operation and Developmenthttp://appli1.oecd.org/olis/2007doc.nsf/linkto/env-jm-mono(2007)14 [accessed 26 March 2009]

Roush RT. 1994. Managing pests and their resistance to Bacillus thuringiensis: Can transgenic crops be better thansprays? Biocontrol Sci Tech 4:501-516.

Roush RT. 1997. Bt-transgenic crops: just another pretty insecticide or a chance for a new start in resistancemanagement? Pestic Sci 51:328-334.

Singla, R, Johnson, P and Misra, S. 2010. Efficient Refuge policies for Bt cotton in India. Agricultural & AppliedEconomics Association. 2010AAEA, CAES, & WAEA Joint Annual Meeting, Denver, Colorado.

Soberón M, Pardo-López L, López I, Gómez I, Tabashnik BE and Bravo A. 2007. Engineering modified Bt toxins tocounter insect resistance. Science 318:1640-1642.

Tabashnik BE, Johnson KW, Engleman JT, and Baum JA. 1996. Cross-resistance of the diamondback moth indicatesaltered interactions with domain II of Bacillus thuringiensis toxins. Appl Environ Microbiol 62:2839-2844.

US-EPA. 2001. Biopesticides Registration Action Document – Bacillus thuringiensis plant-incorporated protectants.United States Environmental Protection Agency. http://www.epa.gov/oppbppd1/biopesticides/pips/bt_brad.htm[accessed 26 March 2009]

US-EPA. 2006. Insect Resistance Management Fact Sheet for Bacillus thuringiensis (Bt) Corn Products.(http://www.epa.gov/oppbppd1/biopesticides/pips/bt_corn_refuge_2006.htm) [Accessed 26 March 2009]

Van Rie J, McGaughey WH, Johnson DE, Barnett BD, and Van Mellaert H. 1990. Mechanism of insect resistance tothe microbial insecticide Bacillus thuringiensis. Science 247:72-74.

Yu SJ, The toxicology and biochemistry of insecticides. CRC Press, Boca Raton, FL (2008).

Walters FS, Stacy CM, Lee MK, Palekar N, and Chen JS. 2008. An engineered chymotrypsin/cathepsin G site indomain I renders Bacillus thuringiensis Cry3A active against western corn rootworm larvae.Appl Environ Microbiol 74: 367-374.

Wu KM and Guo YY. 2005. The evolution of cotton pest management practices in China.Ann Rev Entomol 50:31-52.

Zhao JZ, Cao J, Collins HL, Bates SL, Roush RT, Earle ED, and Shelton AM. 2005. Concurrent use of transgenicplants expressing a single and two Bacillus thuringiensis genes speeds insect adaptation to pyramided plants.Proc Nat Acad Sci USA 102:8426-8430.

12. References

Appendix 1. Summary of key pointsINSECT RESISTANCE MANAGEMENT PLANS• No matter how detailed the results, science alone will not result in a robust insect resistance management (IRM)

plan in the absence of practical field experience, information on local/regional environments and growerpractices.

• IRM plans need to be suitable for the given production situation.

• The goal of IRM is to enable growers to have access to the technology, while providing stewardship that willensure an acceptable level of protection against resistance.

• The adoption of Bt crop IRM plans has been largely successful because they were developed with broadstakeholder participation.

PYRAMIDING INSECT RESISTANCE TRAITS• Where pyramiding strategies for insect control traits consists of the simultaneous use of two insecticidal agents

with different modes of action against the same target pests, these can be used to reduce the development ofinsect resistance.

• Where stacked genes target different pests, there is no IRM advantage and the full refuge requirements are stillneeded.

REDUCING THE RISK OF PEST RESISTANCE• Monitoring the adoption rate of insect protected crops on a regular basis is important for identifying the highest

risk areas.

• The practice of saving a portion of the crop seed harvest for planting in the next growing season can haveimportant negative impacts on resistance management for insect protected crops.

• Without proper QC/QA by a professional seed company, uniform high dose deployment of the trait and even traitpurity can be compromised.

• Insect monitoring encompasses two basic approaches: monitoring the insects for changes in susceptibility to thecontrol protein and monitoring fields for signs of unexpected levels of damage due to a key target pest.

• As a first step, measuring the baseline susceptibility of pest populations to the trait across the growing areashould be undertaken prior to widespread planting of insect protected crops.

• Grower monitoring of fields for damage due to the key target pests is an important component of early detectionof resistance.

• Bt pesticides should not be used on biotech-derived, insect protected crops or on refuges serving these cropsif they contain in-plant protection from a Bt protein.

• When pest pressure levels trigger the need for additional control measures, growers should consult localguidelines and chose a control option, or combination of treatments that cause the least impact on beneficialorganisms.

• Growers are encouraged to used local IPM guides to identify appropriate monitoring schedules, the pests to bemonitored, critical economic thresholds for damage, and the recommended alternative control measures.

• Resistance management is the responsibility of all stakeholders.

• It is important that growers be trained through familiar venues that are relevant to their situation, taking intoaccount the culture, language, education levels, avenues of access to information and how products are obtained.

31


32

• Information on the IRM options for the crop are distributed with the seed and it is up to the growers to choosewhich system best suits their growing conditions, cultivation practices and resources.

• Implement appropriate refuges to dilute selection and provide susceptible insects.

USING A REFUGE SYSTEM• If the chosen IRM strategy includes the planting of refuge areas, the layout, the seed needs and the input

requirements must be fully understood and prepared before planting.

• Growers who chose a refuge option for IRM must map out the planting areas and ensure that the volume andproximity of the refuge are in compliance with the growers’ agreement for IRM requirements for each biotech-derived event.

• The IRM refuge requirements for many insect protected crop varieties require accurate planting of specific seedin specific areas on a farm.

ADHERENCE, RECORDING AND REPORTING• It is standard practice for technology developers to monitor adherence with the IRM strategies recommended for

their seed.

• Recording is an important tool for managing the development of insect resistance in insect protected crops.

• Most grower agreements require growers to report unexpected insect activity and damage during the growingseason.

2. Introduction to confined field trials

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Appendix 2. Record of refuge planting

33


34

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Appendix 3. Record of monitoring

Appendix 4. Examples of IRM local andregional programmes

(Sites Accessed June 2011)

Optimum® Intrasect™ insect protection. Product use guide. Insect resistance management (IRM) requirements;U.S.:http://www.pioneer.com/pv_obj_cache/pv_obj_id_D2C111E4B56A20F8559A4D7C9F95C3BF74390500/filename/oipug.pdf

Insecticide Resistance Management in the control of the mosquito vectors of malaria, IRAC:http://www.irac-online.org/wp-content/uploads/2009/09/IRM-control-mosquito-vectors-of-malariaNov10-v1.pdf

IRM for Herculex™, DOW, U.S.:http://msdssearch.dow.com/PublishedLiteratureDAS/dh_003f/0901b8038003fd1e.pdf?filepath=herculex/pdfs/noreg/010-16128.pdf&fromPage=GetDoc

2011 Monsanto IRM Grower Guide for all Bt crops. U.S: http://www.monsanto.com/SiteCollectionDocuments/IRM-Grower-Guide.pdf

IRM & IWM programs for Monsanto IR & HR crops, 2011, U.S.:http://www.monsanto.ca/ourcommitments/Documents/TUG_English.pdf

Programa Refugio de la Asociación Semilleros Argentinos (Argentine Seed Association IRM Program):http://www.programarefugio.com/

EPA IRM Program for Bt field and popcorn, 2006, U.S.:http://www.epa.gov/oppbppd1/biopesticides/pips/bt_corn_refuge_2006.htm#programme

IRM Strategy for Bt corn in the Philippines. Philippines Dept. of Agriculture:http://www.da.gov.ph/n_sub.php?pass=n_agrilaws/mc/MC_17s03.html

IRM strategies for cotton in India. India:http://www.indiaagronet.com/indiaagronet/pest_management/CONTENTS/insecticide_resistance_managemen.htm

National Corn Growers Association’s IRM learning center:http://ncga.com/managing-bt-technology/

Canadian Corn Pest Coalition:http://www.cornpest.ca/

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Date of publication: October 2011

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