Vol.12_No.2 - Pesticide Alternatives Lab - Michigan State University

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Spring 2003 Resistant Pest Management Newsletter Vol. 12, No.2organophosphates in food production, yet approve - oreven champion - the direct exposure of large numbersof people during mosquito vector control operations.Apparently, it is not appropriate to expose people tominuscule residues in the diet, but inhalation andcontact exposure for human health protection is notnewsworthy.When addressing the scope of North Americanresistance development, new regulations dealing withresistance are of critical interest. For example, with thepromulgation of regulations governing the registrationof genetically modified plants containing insecticidalproteins, resistance management plans were required asa prominent portion of the registration portfolio. Withone exception, all of the current conditionalregistrations for genetically modified plants containinginsecticidal proteins have a resistance managementplan based on high dose and refugia strategies (thesingle exception is Mom 863 for corn rootwormcontrol).The European Union has also recently taken somerecent strides to require resistance managementguidelines in its regulatory system. The EU-EPPO-PP1/213(1) guidelines require resistance riskassessment, development, and implementation of aresistance management plan and baseline monitoring ofresistance for all new registrations within the EU. The1996 Food Quality Protection Act (FQPA) also has aprovision for resistance monitoring contained in itsdetails. Essentially this prescription for resistancemonitoring is worded much like a series ofrecommendations of the US Board on Agriculture ofthe National Research Council, one of which statesthat, "Federal agencies should support and participatein the establishment and maintenance of a permanentrepository of clearly documented cases of resistance"(Dover and Croft, 1986). However, to our knowledgeno divisional program within USEPA has everfollowed up on this part of the FQPA law other thanvoluntary reporting of resistance development byregistrants.Presumably one measure of the impact of recentregulations on the availability of resistancemanagement tools is the number of differentformulations, pesticide and biopesticide modes ofaction, effective natural enemies, and othermanagement strategies, tactics, and tools.Approximately 6,000 pesticides have been cancelled orsignificantly mitigated since the passage of the FQPA.On the other hand, the FQPA and related activities ofthe USEPA have accelerated the registration ofreduced-risk pesticides and organophosphatealternatives. Unfortunately however, this legislationhas also practically eliminated the experimental usepermit process whereby land grant universities, privatetechnical service providers, and commodity researchershave historically adapted new pesticide tools to variousproduction systems. In addition, the FQPA hasprovided an array of new risk-science developmentsestimating the aggregate exposure to pesticides thatexhibit common modes of action, the cumulativehuman pesticide exposure over a lifetime, and theimpact of endocrine disruption on non-targetorganisms. Potentially all of these risk-scienceinnovations could have unique or integrated impacts onresistance and resistance management in NorthAmerica as the USEPA evolves these policies.As previously mentioned, resistance is a geneticbaseddecrease in the susceptibility of a population to acontrol measure. It has been observed acrossherbicides, fungicides, and bactericides, as well asinsecticides and miticides. An array of evolving pestbiotypes or races has also overcome conventionallyselected host plant resistance crop varieties. Perhapseven cultural control strategies like crop rotation maybe overcome by genetic adaptation in a pest. An arrayof adapted ecosystems, particularly resistant soils, hasalso evolved to pesticides. The economic, social, andenvironmental consequences for the various types ofresistance include pest control failures, disrupted pestmanagement systems (including limitations in thedevelopment of integrated pest management options),and increased pest control costs. Increased pest controlcosts have variously been classified as 1) pestmanagers forced to resort to newer, higher-pricedpesticide alternatives and 2) additional applications.Certainly, there are arrays of environmental,social, and disrupted functional ecosystemconsequences of increased pesticide use induced byresistance. Functionally, disrupted ecosystems andenvironmental impacts could be measured in increasedoff-target effects on bio-diversity and/or endangeredspecies. Additional social impacts may includeconsequences on humans from increased pesticideresidues, worker exposure, or increased disease spreadwhere vector control is diminished as a result ofresistance.In summary, globalism and environmentalism willlikely continue to impact the availability of pesticidesas well as the social and economic determinants thatwill dictate overuse of pesticides leading to resistance.Heightened concerns over homeland security,particularly in the United States, may have collateraleffects in terms of fighting bio-terrorism withadditional pesticide use. Certainly the emergence ofbiotechnology and genetically modified organisms withvarious pest selection processes could result in furtherexpansion of resistance problems. On the other hand,monitoring and diagnostics in resistance managementshould improve dramatically with the application ofnew high-through-put technology developed initiallyfor HIV/AIDS and cancer detection. In addition, thepesticide industry, though market and regulatoryincentives, is beginning to deliver an expanding array4
Spring 2003 Resistant Pest Management Newsletter Vol. 12, No.2of novel and ecologically softer pesticides. This freshcollection of new modes of pesticide action shouldallow pest managers a greater diversity of managementtools to focus on target pests, thereby reducing the rateof resistance selection. Obviously the dissemination ofvarious regulations will continue to impact theavailability of resistance management tools.Certainly, society is witnessing the rapid andexpansive response of the private sector to reduced-riskand organophosphate-alternative incentives through theUSEPA. One might only speculate on the developmentof new resistance management strategies, tactics, andtools if some of the focus and resources currentlyemployed to regulate pesticides in North Americansocieties are actually allocated to monitoring andmeasuring resistance, the loss of susceptibility inresistant-prone species, or the dysfunctionalecosystems resulting from resistance development. TheCAST Resistance Conference highlighted severalefforts to document resistance development in weeds,fungicides, and arthropods. These efforts are essentialfrom our prospective, because "what gets measuredgets managed."Robert M. Hollingworth &Mark E. WhalonCenter for Integrated Plant SystemsMichigan State UniversityEast Lansing, MI 48824-1311USAResistance Management ReviewsManaging Phosphine Resistance in Grain Insects with the Phoscard®Export grain is one of the mainstays of Australianagriculture with over 80% of grain produced byAustralian growers destined for export. Unfortunatelythe warm storage conditions in Australia are conduciveto the establishment and development of grain insects.Australia's enviable record as an exporter of cleangrain has been achieved through the judicious use ofpesticides, fumigants, and general storage hygiene.More recently our customers have begun to demandgrain that is free from chemical residues as well asfrom insects and this has created challenges for graingrowers, handlers, marketers, and researchers.Australia is largely satisfying these markets forresidue-free grain with the use of fumigants,particularly phosphine. In Western Australia (W.A.)sealed storages are used on over 60% of farms and asimilar percentage of Bulk Handling storages aresealed. Since 1990, all grain has been exported fromW.A. without the use of contact insecticides at anystage during storage.This reliance on phosphine at all stages of storageplaces a lot of pressure on a single fumigant,particularly with respect to resistance development.Worse still, there are few alternatives - the use of the"fall back" fumigant, methyl bromide, is soon to beheavily restricted or terminated completely.Researchers around the world have shown that theineffective use of phosphine in poorly sealed storagescan lead to resistance and eventually control failures. InRob EmeryEntomology BranchDepartment of AgricultureWestern Australiathe early 1980's highly resistant strains of lesser grainborer were found in Bangladesh where phosphine hadbeen used for many years.Early research in Western Australia has shown thatgrain insect resistance rarely develops in bulk storagesbecause the cost and return of fumigating largeamounts of grain is so high that bulk handlers makesure the job is done correctly the first time, every time.In the past, resistance has developed on-farm wheregrain protectants and fumigants are not always used inaccordance with the label. There is a danger that thesestrains could find their way from the farm into thecentral handling system or worse still, an exportmarket.Bulk handlers routinely monitor the gasconcentrations in storages under fumigation throughoutthe fumigation period; this is the key missing factorfrom farm fumigations.Gas detection/monitoring equipment is often seenby farmers as being too expensive, too difficult tomaintain and calibrate, and too sensitive to the rigoursof day-to-day farmer use.As an alternative to monitoring, the currentrecommendation is that farmers pressure test theirstorages to assess the gas-tightness of the structureprior to fumigation. If the storage is sufficiently wellsealed, we know that an effective fumigation will takeplace provided the storage is kept sealed for 7-10 days.Unfortunately, from a farmer perspective, this pressure5
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