wide area pest management

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pressure applied against the totalpopulation of the pest over a period ofgenerations will achieve greatersuppression than a higher level ofcontrol on most, but not all, of the

population, each generation. Therefore,it is very important to eliminate anyplaces of refuge or foci of infestationfrom which recruits could come to re-establish damaging densities of the pestpopulation in areas of concern.

For the most part, the control ofmany highly mobile and very destructivepests is carried out by individualproducers who rely heavily on the use ofinsecticides. Although other control

technologies are often incorporated intothe producers integrated pestmanagement (IPM) system, thesetechnologies, too, are usually applied byproducers independently of otherproducers. Such an uncoordinated farm-by-farm IPM strategy providesopportunities for the pest population tobuild up and to establish damaginginfestations in well-managed fields.Consequently, on most farms insectpest populations increase to damaginglevels each year, and the farmer is

forced to apply broad-spectrum fast-acting insecticides as a rescuetreatment (Table 1). This defeats theprimary goal of the IPM system, which isto take maximum advantage of naturally

occurring biological control agents.Moreover, application ofinsecticides when an insect pestpopulation reaches the economicthreshold does not prevent the lossesthat occur before the threshold has beenreached. For commodities that areplanted on vast areas, such losses inaggregate are immense. For example,the world production of corn (maize) isroughly 600 million metric tons.

Avoidance of a loss of 3% would makeavailable 18 million metric tons, whichcould be a major factor in alleviatinghunger.

Area-wide pest managementdiffers from the conventional pestmanagement of local pest populations inseveral important ways. The area-widestrategy focuses on managing the insectpopulations in all of the niches in whichthey occur, while the conventionalstrategy focuses narrowly on protectingthe crop, livestock, people, buildings,

Table 1. Some examples of crop losses caused by insects. Percent crop losses in theUSA caused by various insect pests without and with control measures.Commodity Pest Percent Loss

Without Control With Control

Bean Helicoverpa zea 37.0 6.0Bean (snap) Epilachna varivestis 20.0 9.9Beet (sugar) Tetanops myopaeformis 22.7 8.2Corn (field) Diabroticaspp. 15.7 5.0

Corn (field) Ostrinia nubilalis -- 2.0Corn (field) Helicoverpa zea -- 2.5Cotton Helicoverpa zea -- 4.0Cotton Pectinophora gossypiella 35.5 10.0Peanut Helicoverpa zea -- 3.0Soybean Pseudoplusia includens 15.7 4.8Sugar cane Diatraea saccharalis 28.6 8.0


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etc., from direct attack by pests. Thearea-wide strategy requires detailedmultiyear planning and an organizationdedicated exclusively to implementingthe strategy. The conventional strategy

involves less planning, tends to bereactive, and is implementedindependently by individual operators orhouseholds. The area-wide strategytends to utilize advanced technologies,whereas the conventional strategy tendsto rely on traditional tactics and toolsthat can be reliably implemented bynon-specialists.

The use of separateorganizations to conduct area-wide

programs provides opportunities toutilize sophisticated technologies andprofessional management. Computer-based models are utilized in planningand management. Satellite imagery isused in area-wide programs to identifylocalities of alternate hosts that can betreated to reduce pest populations thatproduce migrants that cause thedamage in commercial productionareas. Area-wide programs acquire ordevelop highly sensitive detectionsystems, and employ geographicinformation systems software to helpmanage data. They may implementapproaches to prevent or retard thedevelopment of insecticide resistance orloss of host plant resistance. Computerprograms and real-time environmentaldata to predict insect populations can beeffectively used in an area-wideprogram but usually not on an individualfarm basis. Thus, pest immigrationpatterns, analysis of weather to predictincrease or decreases of populations,genetic analysis to determine resistancelevels, etc., are utilized in area-wideprograms.

Finally, area-wide programs areable to take advantage of the power and

selectivity of specialized methods ofinsect control that for the most part arenot effective when used on a farm-by-farm basis. These include the sterileinsect technique (SIT), certain programs

of inundative releases of parasites,semiochemicals, mating inhibitors, largescale trap cropping, treatment of hostson public lands and in private gardens,etc.

Benefits of area-wide pestmanagement

Experience has shown that pestsuppression on an area-wide basis canbe more effective than on a farm-by-

farm basis for reducing losses causedby highly mobile pests and for capturingthe benefits of highly mobile naturalenemies. Area-wide programs enablemany producers to pool resources inorder to utilize technologies andexpertise that are too expensive forindividual producers. These may includemass rearing facilities, aircraft,information technologies and highlytrained specialists. In addition, acoordinated area-wide program canachieve the avoidance or internalizationof external costs. External costs(externalities) are the harmful effectsarising from pest control operations thataffect parties other than the pest controldecision maker, but for which nocompensation is paid to the personsharmed. For example, spray drift ontoneighboring properties frequentlyprovokes disputes. Also, pesticide useto protect agricultural crops has causedinsecticide resistance to develop ininsect vectors of disease.

Finally, economies of scale canbe captured in area-wide programs,although complex trade-offs may beinvolved. The more mobile the pest andthe more uniform the damage caused by


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the pest, the larger can be the areaunder coordinated management. Thetotal costs of pest detection andmonitoring and suppression per hectareof crop usually decline as the size of the

managed area increases. However, theper hectare organizational costs usuallyincrease as the project size increasesbecause of the increased need formeetings and other communicationcosts. For these reasons, in very largeprograms such as the effort to eradicatethe cotton boll weevil from the USA, thevast area was subdivided into a numberof zones. Also, considerableorganizational cost savings may be

realized in instances where towns,municipalities or cooperatives alreadyhave structures in place forcommunication, decision-making,collection of fees, etc.

Contingencies often dictate changesin strategy

Contingencies often arise thatrequire replacement of one strategy withanother. For example, at various timesduring the 43-year campaign to removethe screwworm from the United States,Mexico and Central America, differentpest management strategies had to beselected. This program began when anunusual series of frosts beginning earlyin December 1957 killed all screwwormsin the southeastern USA north of a linein southern Florida from Tampa to VeroBeach. Sexually sterile flies from aculture in a research laboratory werereleased in a broad band north of thisline to contain the pest population whilea high capacity rearing facility was beingreadied. This containment strategy wasreplaced by the strategy of eradicationin the summer of 1958 when the massrearing facility was able to produce 50

million sterile flies per week, anderadication was accomplished in 1959.

A similar change of strategieswas employed in eradicating thescrewworm from west of the Mississippi

River. Beginning in 1962, the parasitepopulation was strongly suppressednorth of the U.S. border with Mexico,and the influx of flies from Mexico wasretarded by the release of sexuallysterile flies in a 130 km-wide zone alongthe entire USA-Mexico border. (Forpolitical reasons in 1966, the U.S.Secretary of Agriculture declared thescrewworm to be eradicated from theUnited States, even though it was

obvious to entomologists that unless theparasite was removed from northernMexico, it would continuously reinvadethe United States.) However, theeradication strategy could beimplemented soon after thegovernments of the USA and Mexicoreached an agreement in 1972 toeradicate the parasite as far south asthe Isthmus of Tehuantepec. Operationsagainst the screwworm in Mexico beganin 1974, and the last screwworm caseoccurred in the United States in 1982.

In the next phase, thesecontainment and eradication strategieswere employed to eradicate the parasitefrom all of Central America to Panama,where a sterile fly barrier wasestablished in 2001.

Legal authority for area-wide pestmanagement

The legal authority needed forarea-wide and other regulatoryprograms is still evolving. In about 1860,the grape phylloxera, Phylloxeravitifoliae(Fitch), was transported fromthe United States to France. Within 25years of its arrival, this insect haddestroyed 1 million hectares of


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vineyards or fully one-third of thecapacity of France to produce grapes. Inorder to protect the German wineindustry, the government of Germany in1873 passed the first law that provided

for quarantines and regulatory control ofagricultural pests. Other governmentsquickly followed the example set byGermany. In 1881 representatives ofmany European countries met anddeveloped a set of regulationsgoverning the movement of grapepropagating material.

In about 1880 the San Josescale, Aspidiotus perniciosusComstock,was established in California. Its rapid

spread throughout the country onnursery stock, and the failure of aprogram to eradicate it, caused Canada,Germany and Austria-Hungary toprohibit the admission of American fruitand living plants beginning in 1898. Thiscrisis led to the passage, by the U.S.Congress, of a series of eleven federalacts beginning in 1905 on quarantineand the regulation of interstateshipments in the USA. In 1999, most ofthese acts were consolidated into theAgriculture Risk Protection Act of 2000.Indeed, most countries adoptedlegislation on: (a) prevention of theintroduction of new pests from foreigncountries, (b) prevention of spread ofestablished pests within the country orstate, (c) enforcement of the applicationof control measures to prevent damageby exotic pests, to retard their spread orto eradicate them. In many countries,the law allows people who wish toorganize a program against a pest tohold a referendum. If the referendumpasses by a certain margin (usually67%) then all parties at interest mustcooperate in the venture.

Currently, in Florida, the programto eradicate citrus canker has been

delayed for several years. Thispathogen is carried considerabledistances on driving rains, and toachieve eradication, the Division ofPlant Industry has found it necessary to

destroy all citrus trees within a radius of578 m from an infected tree.Homeowners in urban areas, who donot understand the need for such drasticaction, feel that workers who enterresidential yards and destroy citrus treesas part of the eradication programviolate their rights. Thus, the BrowardCounty Circuit Court has ruled thatprogram employees must have aseparate court-issued warrant to enter

each privately owned property. Theneed to apply for tens of thousands ofwarrants has prompted the FloridaDepartment of Agriculture andConsumer Services to appeal this ruling.The outcomes of this and other judicialproceedings are likely to more clearlydefine procedures that must be followedin conducting eradication programs, andthe levels of reimbursement owed toaffected homeowners. Unfortunately,the tensions between urban and ruralpopulations caused by the adversarialnature of this process are likely topersist for many years.

Apathy, outrage and area-wide pestmanagement

Some of the programs conductedon an area-wide basis, especially thoseaimed at eradication, have arousedopposition. The strategy of eradicationemerged just over one century ago asthe brainchild of Charles Henry Fernaldof the University of Massachusetts.Under Fernalds leadership,Massachusetts attempted to eradicatean introduced pest, the gypsy moth,Lymantria disparL., in an 11-yearcampaign from 1890 to 1901. Initially,


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the primary eradicant was Paris greenspray. The use of Paris green, whichsuffered from modest efficacy andphytotoxicity, had to be abandonedbecause of adverse public reaction

including threats of violence and massprotests.Those stakeholders who are not

primarily concerned with the economicdimension of the pest problem tend tobe highly concerned with ecological,environmental, social and human healthimplications of area-wide programs.Therefore, leaders of area-wide pestmanagement programs need to behighly sensitive to the perceptions and

attitudes of the public toward certainprogram operations. Often, eradicationefforts must be conducted by the groundrules of the urban rather than the ruralsetting. In programs to eradicate theMediterranean fruit fly in California andFlorida, members of the public stronglyprotested the aerial pesticideapplications even if the same insecticidewas used without dissent for mosquitoabatement. On the other hand, thesame public generally has applaudedthe release of Mediterranean fruit flysterile males.

Normally the public is apathetictowards technological programs.However, certain factors inherent inprograms and in the manner in whichthey are managed can precipitate analmost irreversible shift of the publicsattitude from apathy to outrage. A senseof outrage can be evoked by involuntaryexposure to pesticide residues, imposedlevies or fees, quarantines, right oftrespass, unfair and inequitable sharingof risks, costs and benefits, temporaryloss of control of ones property or fieldoperations, the perception thatendangered species may be harmed,etc.

Acceptance of risk by the publicis more dependent on the publicsconfidence in the risk manager than onthe quantitative estimates of riskconsequences, probabilities and

magnitudes. The publics confidence inthe managers of an area-wide programis of paramount importance.

In each area-wide program, aspecial effort must be made to anticipateand identify those factors that may beemotionally upsetting to various peopleand to take preemptive actions to avoidor mitigate adverse reactions. Publicofficials must be kept apprised, effectivetwo way communication with the public

must occur, surrogates of the publicmust be included in oversight anddecision-making processes, andreferenda may have to be conducted tosecure support and funding for theprogram.

Invasive pests, global trade and area-wide pest management

The rapid globalization of trade inagricultural products, and increasingtourism, have dramatically increased thespread of invasive harmful organisms.We have entered an era of anunprecedented level of travel by exoticinvasive organisms. The greatest harmbeing done by non-indigenous invasiveorganisms is occurring on islands, andmajor pests are becoming establishedwith increasing frequencies on allcontinents except, perhaps, Antarctica.For about one century many countrieshave relied on inspection of arrivingcargo and passengers at the port ofentry as a primary exclusionary strategy.However, volumes of arriving cargo aredoubling every five to six years, and it isnot possible to increase similarly thehuman and other resources devoted toinspection at ports of entry. Clearly


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exclusion at the port of entry is nolonger sufficient to protect against exoticpests, even though a number ofemerging technologies are likely tofacilitate safeguarding activities. Thus, in

order to stem the influx of exotic pests, itis important to shift primary reliancefrom exclusion at the port of entry to off-shore actions, namely on pest riskmitigation in the areas of production andelsewhere, certification at the point oforigin, and preclearance at the port ofexport.

An important approach tooffshore mitigation is the creation ofpest-free areas. Indeed, countries that

export raw agricultural commodities caneffectively remove the threat of exoticpests to the importing country bycreating and maintaining pest-freeareas. A pest-free area is one that lacksa quarantine-significant pest species,and is separated from infested areas bynatural or artificial barriers. There aretwo types of pest-free areas: (1) pest-free zones are large geographic areas,such as the entire country of Chile, thatis certified free of tropical fruit flies ofeconomic importance, and (2) pest-freeproduction fields, that require thedemonstrated suppression of quarantinepests to non-detectable levels. Area-wide pest management is an importanttool for promoting safe trade andcontributing as much as possible to thecomplementary goals of food securityand economic security for all countries.

Requirements to establish pest-free fields of crop production include asensitive detection program,suppression of the quarantine-significantpest to non-detectable levels, strictcontrol of the fields, and safeguards toprevent infestation during packing andtransit to the port of export. Forexample, Florida is able to export

grapefruit to Japan by creating pest-freegrapefruit groves in about 22 counties.Regulatory experts from Japan inspectthe entire process of production,packing and transit. Similarly fruit groves

free of the South American cucurbit fruitfly, Anastrepha grandis(Macquart),have been created in Mossoro, Braziland Guayaquil, Ecuador.

The concept of pest-free fieldsbased on bait sprays and the sterileinsect technique was pioneered duringthe early 1960s against the Mexican fruitfly along the Mexico-USA borderMexico. Also in the early 1960s, theCitrus Marketing Board in Israel

developed a concerted area-wideprogram against the Mediterranean fruitfly that has been able to meet thecertified quarantine securityrequirements of fruit importing countries.Chile used the sterile insect technique torid the entire country of theMediterranean fruit fly, Ceratitis capitata(Wiedemann). By 1980 the entirecountry of Chile had become a medfly-free zone, and since then Chilean fruitsin huge volumes have entered the U.S.market without the need for anyquarantine treatments. This hasdramatically strengthened the economyof Chile. Now Argentina, Peru and othercountries have sterile insect techniqueprograms that they hope will enablethem to become fly-free zones with freeaccess to markets in southern Europe,Japan and the United States. AlsoMexico has used the sterile insecttechnique to get rid of theMediterranean fruit fly. Indeed Mexico isridding large sections of its territory of allfruit fly species of economic importance.The Mexican states of Baja California,Chihuahua and Sonora have been freedof all economically important species offruit flies, so that citrus, stone fruits,


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apples and vegetables are beingexported from these states without anypostharvest treatment.

A more recent, highly significantdevelopment has been the continuous

area-wide release of sexually sterilemale medflies over the Los AngelesBasin and around high-risk ports insouthern Florida. This further reducesthe risk of pest establishment in theseport areas.Selected episodes in the history ofarea-wide pest management

Migratory locusts - Migratorylocusts probably were one of theplagues that caused prehistoric man to

attempt forms of group or area-widecontrol. Because migratory locustswarms can be seen approaching froma distance and descending onto crops, itseems likely that people bandedtogether and used whatever means athand to stamp out as many as possible.No doubt invasions of armyworms,leafcutter ants and other insects causedpeople to cooperate in combating them.In China, since 707 B.C., more than 800outbreaks of Locusta migratoriamanilensisL. have been recorded alongthe floodplains of the Hwang, Huai andChang Jiang rivers. In 1929, anoutbreak devastated 4.5 million hectaresof cropland. Consequently, about 120million people were mobilized to modifythe floodplains by damming, terracingand reforestation. Over almost 30centuries, the Chinese slowly developedan area-wide pest managementprogram that now folds togetherknowledge of biology, ecology,forecasting cultural practices, and watermanagement.

During the late 1920s,catastrophic locust plagues werewidespread in Africa and southwestAsia. Boris Uvarov and Zena Waloff of

the British Ministry of OverseasDevelopment responded by establishingthe International Unit of LocustResearch. This Unit became theAntilocust Research Centre and it

provided the focal point for internationalcooperation in coping with plagues ofthe desert locust, the red locust and theAfrican migratory locust. The Centrecreated databases and provided asustained regular flow of information onthe status of locust populationsthroughout their ranges. The Centredeveloped a system of monthlyforecasting. Uvarov was able to interestthe FAO in creating the International

Desert Locust Information Service tocoordinate forecasting and the planningof campaigns. Leadership in thesevitally important functions has beenassigned to the FAOs Locust.

In recent decades locust expertshave attempted to shift the prevailingstrategy from reactive to proactive, andeventually to outbreak prevention. Thereactive strategy initiates interventionsafter plague status has been reached inorder to contain the magnitude of thedamage. The proactive strategy seeksto prevent the occurrence of plaguestatus by intervening against localizedoutbreaks. Proaction requires earlydetection of bands and swarms,preferably still in breeding areas, andprepositioning of locust campaignsupplies. The outbreak preventionstrategy seeks to intervene before thephase shift from solitary to gregarious.Possibly the outbreak preventionstrategy would rely substantially oninducing epizootics by inoculatingbreeding populations with selectivepathogens. A difficulty in implementingthe proactive strategy and movingtoward the outbreak prevention strategy


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is that donor support tends to wane inthe absence of full-blown plagues.

Insect vectors of humandiseases - Doubtless the scientificpioneers of area-wide approaches were

influenced strongly by concepts from thefield of public health and hygiene. About2,500 years ago the Greek spirit and theRoman capacity for organization hadproduced a highly developed system ofhygiene in what is now southernEurope. The Romans procured safesupplies of water by means ofaqueducts, practiced daily bathing andremoved garbage from cities. Therationale for these measures was

explained by Varro (116-27 BC), whoserved Pompey and Julius Caesar.Varro asserted that minute livingcreatures cause malaria. He wrote: Indamp places there grow tiny creatures,too small for us to see, which make theirway into our bodiesand give rise tograve illness. However, with thecollapse of the Roman Empire and thestorms of folk-migrations, classicalhygiene eroded. Nevertheless, ragingoutbreaks of malaria, typhoid, typhusand bubonic plague during the latterMiddle Ages reawakened concepts ofhygiene and public health. Doctors andpublic authorities joined forces to erectwalls against these plagues. Dr. JohannPeter Frank (1745-1821) hadconsiderable success in persuading therulers of Europe during the late 1700sand early 1800s to establish publichygiene policies and to enforce themvigorously. While only a 21-year oldstudent at the University of Strasbourg,Frank called for systematic action bythe authorities to intervene in the livesof all citizens in order to forestall or haltepidemics. The discoveries of Pasteur,Koch and others on the nature of

diseases were foundation stones forrational policies of public health.

Mosquito-borne diseases -Through collective action withincommunities, even without an overall

national plan and central coordination,malaria in southern Europe and NorthAmerica largely disappeared inconsequence of education, the universaladoption of window screens, destructionof habitats of Anopheleslarvae and thetreatment of all cases with quinine.

Investigations conducted in thelate 1800s and in early years of the1900s on the transmission bymosquitoes of deadly diseases led to

widespread use of area-wide programs.Yellow fever, dengue, filariasis andmalaria were shown to be transmitted byvarious species of mosquito. In 1892Howard, and in 1900 Ross, began torecommend that the habitat of mosquitolarvae over extensive areas be eithertreated with kerosene or drained. Thesepractices were first implemented in westAfrica to combat malaria, and soonadopted by communities in manycountries. Mosquito abatement districtswere pioneered by John B. Smith inNew Jersey. The New Jersey MosquitoExtermination Association, founded in1912, provided the model for theorganization and operation of area-widemosquito abatement districts of whichthere are about 260 in the United Statesand a thousand or more worldwide.

Yellow fever was wiped out inHavana, Cuba, under the leadership ofDr. W.C. Gorgas, who in 1898implemented a strict sanitation programto prevent breeding of the diseasevector, Aedes aegyptiL. Subsequently,Gorgas implemented a program in thePanama Canal Zone against Aedesaegyptiand Anophelesspp. vectors ofyellow fever and malaria, respectively.


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activities of the World Bank, FAO, WHOand UNDP. The Onchocerciasis Fundwas created to accept donations, andthe World Bank oversees it.

The Programme Director is

assisted by seven units: Office ofDirector, Administrative Management,Epidemiological Evaluation, VectorControl, Applied Research, Biostatisticsand Information Systems andDevolution. The latter conducts trainingand coordinates devolution activitieswith participating countries.

The limits of the program areawere extended several times because ofinvasions of infective black flies over

greater distances than initially foreseen.Thus the program area expanded from654,000 km2 in 1974 to 1,066,000 km2by 1990.

Two intervention tactics havebeen employed area-wide: larvicidinglargely by helicopter but also manuallywhere streams are overgrown withvegetation, and treatment of humanswith the microfilaricide, ivermectin.Because the period of developmentfrom egg to pupa rarely exceeds oneweek, larviciding must be carried out ona weekly basis. Seven insecticides areemployed on a rotational basis toprevent the development of resistance.In order to achieve the properconcentration of insecticide in theflowing water, an automatedhydrological surveillance network wascreated and real-time data are fed to anon-board computer to enable the pilot toproperly manage spray operations.

The results of the program havebeen dramatic (Fig. 3). As a result ofthis program, 25 million hectares of landsuitable for cultivation have becomeavailable, and rapid resettlement isunderway. Because vector controloperations were phased out in 2002,

ivermectin remains as the only means ofcontrol.

Chagas disease vectors -Chagas disease, first recognized in1909, has been ranked as the most

important parasitic disease in theAmericas. Although the infection is stilllargely incurable, transmission can behalted by (a) eliminating the domesticvectors, blood-sucking reduviids of thesubfamily Triatominae, and (b)screening blood donors to avoid risk oftransmission through transfusions.Small-scale vector control programsbegan during the 1940s based onspraying the interior of homes with

benzene hexachloride or dieldrin tocontrol the primary vectors, Triatomainfestans(King) and Rhodnius prolixus(Stahl), as well as several other speciesof Triatoma. However, these programssuffered from under-funding andinterruptions of funding, so thatreinfestation occurred.

In 1983 a national program waslaunched in Brazil to eliminate theprimary vector, Triatoma infestans,based initially on use of benzenehexachloride and later on pyrethroids.Although not without difficulties, thisBrazilian program proved to be highlysuccessful, and it inspired an area-wideprogram encompassing the SouthernCone countries (Argentina, Bolivia,Brazil, Chile, Paraguay, and Uruguay)plus Peru. This 10-year program waslaunched in 1991 under the leadershipof the Pan American HealthOrganization with funding, in part, fromthe European Union. Total programcosts were estimated at US $190 millionto $350 million. The programstremendous technical and economicsuccess (internal rate of return of 30 to60% largely based on savings in healthcosts) spurred a similar Central America


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Initiative (El Salvador, Guatemala,Honduras and Nicaragua) and anAndean Pact Initiative (Colombia andVenezuela).

Each program began with a

centrally managed attack phase ofabout three years in which all homes aresprayed by trained professionals,followed by a more community-basedphase, which relies substantially on theefforts of homeowners and localauthorities. Adventitious transmissionmay be accomplished by sylvatic vectorspecies, which can enter houses to formdomestic colonies. In addition, migrantworkers and other travelers can carry

vectors. Currently, vector populations inMexico and the Amazon Basin remainas major challenges. Elsewhere, thefocus is shifting to epidemiologicalsurveillance and care of people alreadyinfected.

Cattle ticks - The discovery in1889 by Theobald Smith and colleaguesthat cattle fever is caused by a tick-transmitted parasite of red blood cellsled to the initiation in 1906 of a county-by-county effort to eliminate the twoBoophilustick vectors (Fig. 4) from theUnited States. Many pastures wererendered tick-free by excluding all hostanimals until all ticks had starved todeath. Livestock were dipped in anarsenical solution at two-week intervals.Quarantines were used to prevent themovement of infested cattle into areasthat had been cleared. By 1943, after 37years of grueling effort, the ticks hadbeen eliminated entirely from the UnitedStates for a total cost of about $40million dollars, or the equivalent of theannual losses suffered before theprogram was initiated. Quarantines havebeen effective in preventing these ticksfrom becoming re-established from theirpopulations in Mexico. A broadly shared

vision sustained this program in spite ofwar and the great economic depression.

Contributions of naturalenemies - Area-wide pest managementbegan to be practiced widely during the

19th century using natural enemies.During the 18th and 19th centuries,people began to understand the roles ofnatural enemies in preventing insectoutbreaks. Further, the powerfulsynthetic insecticides were not availableto allow small holders independently toprotect their crops and livestock. Thebeneficial work of coccinellids and otherpredators had been common knowledgefor centuries, and they were collected

and distributed for insect control. Insectparasitism was discovered only around1700 by Leuwenhoeck in theNetherlands and in 1706 by Vallisnieri inItaly. Emperor Francis 1 of Austriaordered Vincent Kollar to publish hiswork on the role of natural enemies insuppressing pests. Kollars great workappeared in 1837 and the Englishtranslation appeared in LondonsGardners Magazine in 1840.

E.F. Knipling has analyzed thepotential contributions of parasitoids toarea-wide pest suppression. Parasiteaugmentation could be an especiallydesirable preventive measure becausethe release of host specific parasitesposes no danger to humans, beneficialorganisms, or the environment. Highlymisleading conclusions have beendrawn from past augmentationexperiments, because the experimentswere done in small non-isolated areas.Most pest arthropods and parasites orpredators are highly mobile. Therefore,meaningful results can be obtained onlyif augmentation experiments areconducted over large areas. Eventhough many species of natural enemieshave developed efficient host finding by


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following odor plumes of kairomonesemanating from the host, under naturalconditions the level of parasitizationdoes not threaten the host withextinction. Augmentation utilizes the

host resources in nature to producelarge numbers of parasite progeny. Ifdone properly, parasite augmentationfor several generations can become aself-perpetuating suppression measure.Augmentation causes progressiveincreases in the rate of parasitism witheach succeeding parasite generation,provided that the initial rate of parasitismis above 50%. In addition, a host-dependent species will tend to distribute

itself proportionally to the distribution ofits host. No other method of insectcontrol has the characteristic ofconcentrating its suppressive actionwhere it is most needed.

Lasting suppression of cottonycushion scale by Vedalia beetle - Thatclassical biological control can providearea-wide solutions was dramaticallyillustrated against an exotic pest inCalifornia in 1888 and 1889. At that timean introduced pest, the cottony cushionscale, Icerya purchasi, was killinghundreds of thousands of citrus trees.However Albert Koebele was able tointroduce a scale predator, the vedaliabeetle, Rodolia cardinalis(Mulsant),from Australia and New Zealand. Lessthan 11,000 vedalias were distributed,but they spread throughout the entirecitrus growing area of southernCalifornia and saved the industry. Thevedalia beetle continues to effectivelyprotect citrus in California, and nothingneeds to be done other than to avoid theuse of certain insecticides, which woulddecimate this invaluable natural enemy.

Lasting suppression ofcassava mealybug by Epidinocarsislopezi- Almost exactly one hundred

years after the great vedalia success, ateam led by Dr. Hans Herren of theInternational Institute for TropicalAgriculture (IITA) successfullyimplemented the largest classical

biological control program in history. In1973, cassava near Brazzaville andKinshasa was found to be attacked bythe cassava mealybug, Phenacoccusmanihoti(Matile-Ferrero). In a few shortyears immature crawlers were dispersedby wind throughout sub-Saharan Africa.

The cassava mealybug createdstarvation and hardship for many of the200 million people for whom cassavahad become a staple crop. In 1981, an

excellent parasitoid, Epidinocarsis lopezi(DeSantis), found in Paraguay by A.C.Bellotti, proved capable of bringing thecassava mealybug under control. Theparasite was mass-reared and releasedby aircraft over 38 countries (Fig. 5) ofsub-Saharan Africa (an area muchlarger than the combined area of theUnited States, Mexico and India) withexcellent results. This singularaccomplishment required strong andimaginative leadership and action byIITA, generous funding by donors, andbrilliant scientific and technical work byHerrens team and their cooperators inAfrica, Europe, and the Americas.

Area-wide conservation ofpredators of the brown planthopper -In many cases, natural enemies areeffective only if most smallholders in anarea work to conserve them. Becauseboth pests and natural enemies aremobile, their populations distributethemselves throughout the region inwhich their food sources are available.Even smallholders who do notparticipate in the conservation programreceive some of its benefits. They get afree ride, and for them this is a positiveexternality of the program. On the other


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hand, the movement of natural enemiesoff the property of the participatingfarmer to that of the free rider is anegative externality.

The brown planthopper,

Niloparvata lugens(St l), has been thescourge of rice production in southeastAsia for many years. However, duringthe 1980s, Indonesia (with technicalassistance from FAO and GermanysGTZ) simultaneously achievedsubstantial increases in rice productionand major reductions in insecticide use.Generally, brown planthoppers areeffectively controlled by indigenousspiders and other predators. Moreover,

since insecticides have a greater impacton the predators than on the pest, thebrown planthopper populations are ableto resurge after being sprayed. In thepast, farmers induced resurgence bybeginning to spray at 40 days aftertransplanting the rice. However, cagestudies showed that the smallholderwho delays spraying until 65 days aftertransplanting saves two insecticideapplications, and realizes a yield

increase of about two tonnes, for a totalbenefit of US $588 per hectare.It is possible to model what

happens when some smallholders delayspraying to conserve natural enemiesbut others do not. If about 10% ofsmallholders conserve natural enemies,they gain only one-fifth of the potentialbenefit. If 30% of smallholders conservenatural enemies, they gain only one-quarter of the potential benefit, and thefree riders gain about 7%. When 50% ofsmall holders conserve natural enemiesthey gain one-third of the potentialbenefit, and the free riders gain about18%.

When 70% of smallholdersparticipate, they gain almost 60% andthe free riders gain about 40%, and

when 90% participate, they gain about83% of the potential benefit, while thefree riders gain 66%. Clearly, aconservation program is almost futileuntil about one-half of the smallholders

participate, and the program becomesprogressively more beneficial as thepercent participation increases toward100.

Bark beetles - Dendroctonuspine bark beetles are dangerous pestsin forestry because of their mass attackson healthy trees. During the firstdecades in the 20th century, forestersfocused on destroying the developingbroods of potentially destructive beetles

before they could emerge and attackvaluable trees. This was implementedby felling dead trees, peeling andburning the bark or by storing theinfested logs in millponds until theycould be sawed into lumber. The futilityof such attempts by focusing directly onkilling beetles became apparent when,in 1932, an extremely cold winteroccurred and destroyed at least 80% ofthe beetles in western North America.The destruction of the beetle broods byfrost was more complete, extensive anduniform than could be accomplished byforest managers. Yet, within two yearsthe beetle populations had resurged andwere again killing ponderosa pine on avast scale.

However, forest entomologistsrecognized that the most vulnerabletrees were those that lacked vigor orwere in decline. Thus, in 1937 control ofbark beetles based on susceptibility oftrees to attack was pilot tested inCalifornia by a program calledsanitation-salvage logging. In thisapproach, up to 20% of trees at highestrisk of beetle attack were removed andsawed into lumber. During the first yearfollowing the removal of the most


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vulnerable trees, losses to bark beetleswere reduced by 90%, and lossesremained low for at least ten years afterthe selective logging.

Boll weevil eradication in the

USA - E.F. Knipling, with the support ofthe National Cotton Council, wasdetermined to eradicate the boll weevilfrom the United States because theweevil necessitated the use on cotton ofone-third of the insecticides used in U.S.agriculture. Also, highly insecticide-resistant boll weevil populations hademerged. Newsom and Brazzel, atLouisiana State University, haddiscovered that in the fall of the year the

boll weevil enters a reproductivediapause and hibernates in trash alongthe edges of cotton fields. Brazzelshowed that the number of weevilssurviving the winter is reduced 90% ifinsecticides are applied just beforediapausing weevils leave the fields.Moreover, Kniplings analysis showedthat if insecticide sprays were targetedalso to kill the generation producingindividuals going into diapause, then thenumber overwintering would be reducedby more than 99%. Kniplings modelwas verified, and this ignited greatinterest in actually eradicating the bollweevil. An effective pheromone-baitedtrap was developed for detection.Weevils were sexually sterilized with theanti-leukemia drug, busulfan.

In 1971-1973, a large pilot fieldexperiment to assess the feasibility oferadication was centered in southernMississippi. The eradication zone wassurrounded by three buffer zones. Veryintensive suppression was implementedin the two inner zones, and farmerswere expected to practice diligentcontrol in the outer zones, althoughsome grew cotton simply to qualify forgovernment payments and with no

intention to harvest a crop. Only oneapplication of the suppressive systemwas made, because of a shortfall inappropriations. Nevertheless, the bollweevil was suppressed below

detectable levels in 203 of 236 fields inthe eradication zone. All of the 33 lightlyinfested fields were located in thenorthern one-third of the eradicationzone and less than 40 km fromsubstantial populations farther north. Inthe southern two-thirds of theeradication zone, no reproduction couldbe detected in any of the 170 fields.Knipling and some others concludedthat the available technology was

sufficiently effective to achieveeradication. Their experience with thescrewworm indicated that eradicationcould be accomplished iteratively,following an application of thesuppressive system that clears the pestfrom most of the target zone. Next,surviving populations are delimited andsimilar suppressive measures areapplied to them. In this iterative fashion,the aggregate range occupied by thepest is progressively reduced towardzero. However, some felt that thetechnology was not adequate to mountan eradication campaign, unless asingle application of the system ofsuppression eliminated all weevils in thetarget zone.

A Cotton Study Team appointedby the National Academy of Sciencesdrafted a very negative interpretation ofthe results. Because Knipling was amember of the Academy, he had accessto this draft, and he wrote a strongrebuttal. Therefore, the Cotton StudyTeam wrote a toned down statementthat continued to express strongreservations about the feasibility oferadicating the boll weevil, butconcurred to conduct a new trial


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eradication program in North Carolina.Grudgingly the Academy teamlegitimized the concept of continuinglarge-scale eradication experiments, butwith the caveat that they would probably

fail. The new trial program, started in1978 in Virginia and North Carolina, washighly successful. Subsequently, piece-meal programs, each run by a separatefoundation, have removed the bollweevil from about 5 million acres inVirginia and the Carolinas, Georgia,Florida, south Alabama, California, andArizona. These programs have causedsignificant reductions in pesticide usage,

and the eradication efforts arecontinuing. Thus, the job is about halfdone. However, the corrosive effect ofthe Academys report persists. The USCongress reduced the share of federalfunds from the traditional 50% to lessthan 30% of the cost. However, suchcost sharing is no longer guaranteed,and in 1997 the US Department ofAgriculture initiated a program of makingloans to officially recognized boll weevileradication foundations. Moreover, theprocess of eradication is beingconducted piece-meal with a minimumof technology. Pheromone traps areused to delimit infestations, and theattack begins with insecticides appliedlate in the growing season againstweevil still reproducing and thoseentering diapause. As many as 15insecticide applications per year aremade against dense persistentpopulations. Planting by all growers issynchronized and delayed, short seasonvarieties are grown, harvested as soonas possible, and stalks are destroyedimmediately after harvest. Eradication isusually accomplished by the end of thethird growing season.

Attempts to sharply define the area-wide pest management strategy

A few scientists have attemptedto sharply define the area-wide pestmanagement strategy. Knipling stated:

Area-wide pest management is thesystematic reduction of a target keypest(s) to predetermined populationlevels through the use of uniformlyapplied control measures over largegeographical areas clearly defined bybiologically based criteria. D.A.Lindquist wrote: An area-wide insectcontrol program is a long-term plannedcampaign against a pest insectpopulation in a relatively large

predefined area with the objective ofreducing the insect population to a non-economic status.

Both of these definitions haveconsiderable merit and they fit themajority of area-wide programs.However, slightly different definitionsmay be needed to describe programs onthe conservation of natural enemies(which can tolerate some free-riders)and on classical biological control wherethe adaptation of the introducedbiological agent to all new environmentscannot be known in advance of makingreleases. Also, in programs to containan invasive pest population, it may notbe possible to clearly define theboundary of the pest population. In thesimilar vein, A.T. Showler stated:Locust swarms can be highly variable,influenced by many factors, includinggeography, vegetative conditions, land-use patterns, environmental sensitivity,availability of resources and tactics,prevailing winds, insecure areas, andrainfall patterns. Reliance on a singlecontrol strategy is therefore unrealistic.A more appropriate approach would beto develop specific strategies that will fitwith projected scenarios, mostly by


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harmonizing them with nationalcontingency plans. The common threadthat runs through all area-wide pestmanagement programsis the strongemphasis on preventing the existence of

any places of refuge or foci of infestationfrom which recruits can come to re-establish damaging densities of the pestpopulation in areas of concern.

Benefit-cost assessment anddiscounting net returns

Usually, investments in area-wideprograms are made with the expectationthat program benefits will accrue over amulti-year time horizon. Therefore, we

must discount future benefits to balancethem against present or near termexpenditures. The stream of discountedannual benefits and costs for manyyears of an undertaking can be summedup and expressed as a single value,known as the present value net benefits(PVNB). The formula for calculating thePVNB is as follows:

PNVB = NB1 + w2NB2 + w3NB3 + w4NB4+ w

5NB

5+ w

6NB

6+ w

tNB

t+ w

15NB

15

where NBt represents the net benefits inyear t, and wt represents the weightingfactor for year t. The weighting factorsare a function of a discount rate (r):

tr)(1

1

tw

The discount rate is the opportunity cost

of the money, or the interest value thatmoney could earn if allocated to the bestalternative use. This rate may beestablished by subtracting the nationalinflation rate from the bank interest ratefor savings. In normal times, thisprocedure will generally produce afigure around 4 or 5% in developed

countries. This represents thereasonable persons discount on thefuture, because people put their moneyin the bank to gain this premium, andotherwise they would spend it now. So,

the benefit of eradication next year isworth 5% less if it is brought back to thepresent. Benefits in 20 years are onlyworth 37% of their face value whenbrought back to the present. In riskiereconomic environments, discount rateswill be much greater, so the calculatednet present value of future benefits maybe insignificant. However, for sterileinsect technique programs involvingvectors of human diseases, the futures

of groups of people are at stake, and itdoes not seem appropriate to discountbenefits in the manner appropriate forprivate investments. The health of thehuman population 30 years in the futureseems just as important as the health ofthe population at present. Nevertheless,investments in vector control programsmust be subjected to critical analysis inthe interest of efficient and soundmanagement. However, if high discountrates (e.g., 25%) are selectedcommensurate with economic risk inmany developing countries, then it seemunlikely that vector control programs inthese countries would ever be launched.

Kniplings imperativeWhen the World Food prize was

awarded to Knipling and Bushland,Knipling stated: If major advances are tobe made in coping with most of themajor arthropod pest problems, then thetactics and strategies for managing suchinsects, ticks and mites must change.They must change from the current,limited scale, reactive, broad-spectrummeasures to preventive measures thatare target-pest specific and rigidlyapplied on an area-wide basis. Great


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and enduring strides can be made byadopting the strategy of area-wide pest

management to help meet world food,health and environmental challenges.

References

Klassen, W. 1989. Eradication of introduced arthropod pests: theory and historicalpractice. Miscellaneous Publications of the Entomological Society of America 73:1-29.

Klassen, W. 2000. Area-wide approaches to insect pest interventions: history andlessons. Pp. 21-38 in Teng-Hong Tan (ed.), Joint Proceedings of the FAO/IAEAInternational Conference on Area-Wide Control of Insect Pests, May 28-June 2,1998, and the Fifth International Symposium on Fruit Flies of EconomicImportance, June 1-5, 1998. I.A.E.A., Penerbit Universiti Sains Malaysia, Pulau,Pinang, Malaysia. 782 pp.

Klassen, W., D.A. Lindquist, and E.J. Buyckx. 1994. Overview of the Joint FAO/IAEADivisions involvement in fruit fly sterile insect technique programs. Pp. 3-26 in

C.O. Calkins, W. Klassen, and P. Liedo (eds.), Fruit flies and the sterile insecttechnique. CRC Press, Boca Raton, Florida. 272 pp.Knipling, E.F. 1979. The basic principles of insect population suppression and

management. USDA Agriculture Handbook 512. Washington, DC. 659 pp.Knipling E.F. 1992. Principles of insect parasitism analyzed from new perspectives:

practical implications for regulating insect populations. USDA AgriculturalHandbook 693. Washington, DC. 337 pp.

Reichelderfer, K.H., G.A. Carlson, and G.A. Norton. 1984. Economic guidelines for croppest control. FAO Plant Production and Protection Paper 58. FAO, Rome, Italy.93 pp.


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Figure 1. Results of a model that show that outcome of neglecting to suppress a smallfraction of a pest population in an agroecosystem versus the effects of uniformlysuppressing the entire pest population. On the left, 10% of the population is untreatedand it produces a large number of individuals in four generations, while the 90% of thepopulation that is treated declines. On the right, the entire pest population in theagroecosystem is suppressed uniformly and its numbers decline from generation togeneration. (After Knipling, 1972.)

Figure 2. The original area of the Onchocerciasis Programme established in 1974 andthe subsequent western and southern extensions required to exclude migration of theblack fly vectors. (After World Health Organisation, 1994.)


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Figure 3. Actual and projected impact of 15 years of suppressing black fly vectors ofOnchocerciasis in the West Africa Programme. Reproduced from World HealthOrganisation, 1994. CMFL is the community microfilarial load (geometric mean ofmicrofilarial levels in all people in a given community).

Figure 4. Progress in eradicating Boophilusticks in the United States, 1906-1943.


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wide area pest management

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