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

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