Pestic. Sci. 1997, 51, 387È390

There Has Never Been a Better Time or a GreaterNeed for Resistance Management*

K.Paul Leonard

Cyanamid International, Chause� e de Tirlemont 105, B-5030 Gembloux, Belgium

(Revised version received 14 June 1997 ; accepted 16 July 1997)

Abstract : Integrated pest management (IPM) and sustainable agriculture beneÐtfrom selective and environmentally benign crop-protection products. The per-formance of these products, however, is threatened by resistance. If it is to beprevented from standing in the path of progress, resistance must be managed. Asagricultural practices move towards IPM and sustainable crop protection, selec-tion pressure will be concentrated on products which are compatible with thesesystems. Producers, researchers, government and extension workers cannot solvethese complex problems alone. The key to success is collaboration. The Insecti-cide Resistance Action Committee (IRAC) was set up by the crop-protectionindustry in 1984 to promote and co-ordinate its contribution to resistance man-agement. Today, it is collaborating with research institutes, government organis-ations and extension services to combat resistance. IRAC focuses on researchand communication projects which reduce selection pressure, organising work-shops in “resistance hot spotsÏ and providing input to draft legislation. Selectedexamples of IRACÏs collaborative work are described.

Pestic Sci., 51, 387È390, 1997No. of Figures : 0. No. of Tables : 0. No. of Refs : 12

Key words : resistance management, IRAC, IPM, crop-protection industry

1 INTRODUCTION

In 1984, the threat of insecticide and acaricide resistancedevelopment was well known. The scientiÐc literatureon resistance was abundant. There was, however, nocollective forum for addressing this problem within thecrop-protection industry. As a result, meaningful col-laboration was difficult.

Substantial progress has been made over the lastdecade. Today, the situation is quite di†erent. Pro-ducers, academics, advisers, distributors and farmers areworking together to reduce the threat of resistance.

This paper documents some of the many ways inwhich industry, through the Insecticide Resistance

* Based on a presentation at the Conference “Resistance Ï97ÈIntegrated Approach to Combating ResistanceÏ organised bythe Institute of Arable Crops Research in collaboration withthe SCI Pesticides Group and the British Crop ProtectionCouncil and held at Harpenden, Herts, UK on 14È16 April1997.

Action Committee (IRAC),1 is bringing together thosewho share the objective of managing resistance. In par-ticular, it provides an insight into the ways in whichIRAC will focus its resources over the next Ðve years.

2 THE NEW URGENCY FOR RESISTANCEMANAGEMENT

Integrated pest management (IPM) and sustainableagriculture rely, to a greater or lesser extent, on alimited spectrum of the most selective and environ-mentally benign crop-protection products. The per-formance of these products, however, is threatened byresistance. As the move towards IPM and sustainablecrop protection continues, selection pressure will beincreasingly concentrated on these products. The recentdevelopment of resistance by codling moth (Cydiapomonella L.) to widely used insecticides in the south-east of France2h4 provides an example of how resist-ance can limit product choice and threaten the future of

3871997 SCI. Pestic. Sci. 0031-613X/97/$17.50. Printed in Great Britain(

388 Paul K. L eonard

IPM. As codling moth became increasingly resistant toselective products like phosalone and diÑubenzuron,growers turned to various combinations of broad-spectrum organophosphates for acceptable pest control.However, by doing this, IPM practices were compro-mised.

To prevent resistance from standing in the path ofprogress in this way, it must be managed. Those whodetermine product use patterns must recognise the risksposed by resistance and work together to maintain thebeneÐts that environmentally selective crop-protectionproducts provide.

3 MEETING THE CHALLENGE THROUGHCOLLABORATION

Collaboration is the key to success. IRAC was formedin 1984 because the crop-protection industry recogniseda need for co-operation to combat resistance problems.For example, the spirit of co-operation that was createdenabled IRAC to broker an historic initiative with thedevelopment of four new acaricides in 1994 (see below).

To illustrate IRACÏs collaborative approach to resist-ance management, three areas of activity are outlinedbelow:

3.1 Prevention of acaricide resistance

Although there were marked di†erences in their chemi-cal structures, four novel acaricidesÈtebufenpyrad,fenazaquin, fenpyroximate and pyridabenÈappeared toshare a mode of action. In-house research and contem-porary publications indicated that these compoundsacted at the same rotenone site in the mitochondrialelectron-transport chain.5h9 With a long history ofresistance development, the potential for spider mites todevelop cross-resistance to these mitochondrialelectron-transport inhibitors (METIs) was recognised.

No one company involved with these compoundscould tackle this alone. What was needed was acommon resistance management strategy for all fourcompounds. IRAC responded to this challenge byrecommending a radical solution. Member companiesagreed to limit applications to one METI applicationper location in any one year. In order to gain maximumcompliance, it was agreed that competitor productsshould be referred to by name on each otherÏs labels.Having agreed the strategy, the next challenge was tocommunicate it in a way that made a di†erence. Thestrategy was published at the Brighton Crop ProtectionConference in 1994.10

To build on this recommendation, the Institute ofArable Crops Research at Rothamsted in England wascommissioned to develop and validate a resistancemonitoring method and quantify baseline responses.

With a rapid bioassay method now in place for three ofthe four METI compounds, we are well placed to reactshould resistance development be suspected in Europe.

This unprecedented level of inter-company co-operation was made possible by IRAC, and provides animportant benchmark in the history of resistance man-agement, as it was in place before resistance had devel-oped in Europe.

3.2 The risk of malaria being transmitted by resistantmosquitoes

For decades there has been little evidence that resist-ance development by malaria-carrying mosquitoes canbe managed. This has resulted in a lack of agreement asto how best to manage this important threat to humanwelfare. This challenge is now being addressed througha project jointly funded by insecticide manufacturersfrom Europe, Japan and the USA, with IRAC providingadditional Ðnancial support. A large-scale resistancemanagement programme is now in progress in Chiapas,Southern Mexico. Baseline sensitivities of the malariavector Anopheles albimanus Weid. are being measuredby bioassay and biochemical assays as part of a three-year laboratory and Ðeld programme.11 The aim of thestudy is to compare development of resistance in iso-lated populations subjected to varying treatmentregimes. The response of these populations will providea unique insight into how best to develop and monitorresistance management strategies for malaria vectorcontrol.

The initiative draws together expertise and resourcesfrom insecticide manufacturers, the World HealthOrganisation (WHO), Centro De Investigacion DePaludismo in Mexico, the University of Wales andIRACÏs Public Health and Vectors Working Group.IRAC created the environment that made such globalcollaboration a reality.

3.3 Communication of the need to manage resistance

Unless growers and pest-control operators can be per-suaded to change the ways in which they select and useagrochemical products, resistance management will notsucceed. Mindful of this, IRAC has carefully evaluatedthe way in which it communicates with such people. Ananalysis of the distribution of IRACÏs Ðnancial supportdemonstrated that a disproportionate e†ort was beingplaced on research projects and too little e†ort wasfocused on communicating resistance managementguidelines.5 It became apparent that IRACÏs traditionalmeans of communicating, via scientiÐc and industrialpublications, was not e†ective. A new way of reachingpeople on the front line of resistance management, i.e.growers and advisers, had to be identiÐed.

T he need for resistance management 389

In order to render the technical language used byresistance researchers more accessible to non-scientiÐcpersonnel, IRAC enlisted the assistance of Fleishman-Hillard, a leading public relations company in the USAwhich specialises in communicating with growers anddistributors. This collaboration resulted in the pro-duction and distribution of thousands of posters andleaÑets highlighting the problem, with practical adviceon how to limit resistance development. The leaÑet fea-tures the slogan, “ThereÏs only one alternative to resist-ance managementÈresistance management is up toyouÏ. It aims to provide practical advice on the natureof resistance and how it may be avoided. In order toreach the widest possible audience, it is being translatedinto a range of languages for distribution around theworld. In addition, an education pack including 35-mmslides and video presentations will be made available.IRAC is currently considering how best to disseminatethis material.

IRAC has recognised the need to address its messageto a wide range of people at all levels throughout theagrochemical community. Its CommunicationsWorking Group is actively pursuing a range of commu-nication initiatives including :

(i) sponsorship of the Resistant Pest ManagementNewsletter (edited by Michigan State University),which is received by 2600 researchers, advisersand Government workers around the world ;

(ii) ensuring e†ective communication within theIndustry. IRACÏs members include the worldÏsleading manufacturers of crop-protection pro-ducts. Each company representative is chargedwith promoting resistance management in his orher own organisation. In particular, we targetthose developing product-use patterns ;

(iii) publication of the results of IRACÏs world-wideresistance survey.12

4 FUTURE FOCUS AND PRIORITIES

IRACÏs continued success depends on its ability tofocus. With a seemingly endless spectrum of actual orpotential cases of resistance to work on, IRAC mustconcentrate on activities which will have the greatestimpact. Over the next Ðve years, IRAC plans to concen-trate its resources in the following areas :

4.1 Resistance management guidelines

IRAC has developed a series of resistance managementguidelines. These are intended to be used as a basis formore speciÐc strategies to suit individual croppingsystems. They will be published through leading nation-al and international journals. IRAC is also working

with the Global Crop Protection Federation (GCPF) tomake these guidelines and other up-to-date informationavailable via a home page on the Internet.

4.2 Workshops in resistance “hot spotsÏ

There are recognised locations, known as “hot spotsÏ,where resistance develops rapidly and considerablyshortens product life. IRAC is in the process of settingup workshops in such locations in collaboration withlocal universities and extension services to reduce thisproduct wastage. For example, IRACÏs Fruit CropsWorking Group convened a workshop in Le� rida, Spainwhere the European red spider mite (Panonychus ulmiKoch) rapidly developed resistance to clofentezine andhexythiazox. With the recent introduction of METIacaricides in this area, it is the right time to ensure thatthe need for resistance management is understood byall.

4.3 Continued support of resistance management andIRAC activities

Resistance management is like any other commercialactivity. It requires expertise, time and investment. Inthe case of IRAC, member companies contribute aboutUS $90 000 per annum through subscriptions. However,the greatest contribution is made in kind through timespent on IRAC projects. Results need to be clearlyvisible for companies to justify their continued supportof IRAC and resistance management. This means thatIRAC must promote its activities and collaborations sothat its success is recognised. The GCPF home page isone of the ways in which this will be done.

4.4 Assessing the risk posed by resistance

Based on its knowledge of the compounds, their usepatterns and biochemistry, the crop-protection industry,through IRAC, is ideally placed to assess the risk posedby resistance to insecticides and acaricides. With amassive investment in research and development, agro-chemical producers cannot a†ord to ignore this risk.Equipped with this knowledge, IRAC has the motiva-tion, means and commitment to tackle this problemhead-on. The examples above provide evidence of this.

IRAC does not regard legislation as the most appro-priate tool for resistance management, but is, however,keen to o†er expert advice if legislation is to be drafted.With a wealth of experience built up over more than adecade, IRAC is uniquely qualiÐed to provide advice onthe practicality and likely impact of draft legislation.

390 Paul K. L eonard

5 SPONSORSHIP

Ultimately, resistance management is only e†ective if itresults in reduced selection pressure. Resistance man-agement activities which do not in some way reduceselection of resistance genes are not worth supporting.

In future, proposals for IRAC funding will be evalu-ated on their ability to reduce selection pressure. Thoseproposals that are likely to result in the greatestreduction in selection pressure will receive the highestpriority for funding. The current round of IRACfunding will be complete at the end of 1997, so thatfunds will therefore be available for new collaborativeprojects from 1998 onwards.

6 CONCLUSIONS

The crop-protection industry is aware of the risks posedby resistance and is ready to play its part in meetingthis challenge. Through having a common objective andby working together, it has been possible to make sub-stantial progress in the struggle to combat resistance.The industry is keen to work, through IRAC, withorganisations and individuals sharing the objective ofresistance management. It is essential that this progressis consolidated and that we continue to take strength inour e†orts to tackle resistance.

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