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

Spring 2003 Resistant Pest Management Newsletter Vol. 12, No.2testing bears little relationship to the actualfumigation that appears successful becauseall the adults are dead. The trap of course isthat the eggs and pupae will very likely havesurvived the fumigation and are waiting inthe wings to turn into adults and reinfest thegrain within days.With support from the Department ofAgriculture Grains Program and the GrainsResearch and Development Corporation, wedecided to develop an extension tool in theform of a farm fumigation card that wouldoutline key points for conducting a safe andeffective fumigation. The card would alsohave an indicator strip that would givefarmers a "no frills" assessment of thestandard of their fumigation.The fact that phosphine gas corrodescopper is well known, the label even warnsagainst using phosphine around copperelectronic components. Early quarantinefumigation manuals from the United Statesrecommend placing a shiny penny inside railwagons before fumigation to give anindication of success at the end.We began experimenting with variousforms of copper until we found one thatgave an obvious response after exposure tolethal concentrations of phosphine for atleast 7 days. Copper used in electroniccircuit boards gave the best results and couldbe readily applied as a strip to plastic card.We tested the cards in over 20 sealedand unsealed farm storages. The copper stripconsistently indicated successfulfumigations. Figures 1 and 2 show typicalresults for good and poor fumigationscarried out over 7 days.The Phoscard® is styled on a creditcard with the front side bearing 5 keyfumigation principles (Figure 3). Thebackside (Figure 4) has a copper strip that isprotected from tarnishing by a layer oftransparent adhesive tape that must be removed beforeuse. There is a hole to attach string for retrieval andinstructions for use.Farmers can place a Phoscard® in storage prior tofumigation. If the copper strip is exposed to sufficientphosphine concentrations for at least 7 days, the shinycopper strip will turn almost completely black. In fact,it could end up looking like the inside of a car exhaustpipe - evenly coated with a black sooty substance, andin some cases verdigris may develop giving the copperthe distinctive blue/green colour often seen on corrodedcopper pipes. There is a colour chart printed alongsidethe copper strip to allow easy comparison.If the strip has not turned black at the end of thefumigation something has gone wrong: usually a leakystorage or insufficient number of aluminium phosphidetablets being placed in the storage. Remember,fumigate the storage space not the grain, use the samedose whether the storage is full or empty, and regularlyinspect and replace rubber seals.The Phoscard® is an extension tool for farmers. Itwill not replace phosphine monitoring equipment andis not intended to be used by fumigators or bulkhandlers. However, we are hopeful that farmersexperiencing fumigation failures indicated by thePhoscard®, will seek advice on how to improve theirfumigations. The cards will introduce farmers to thevalue of fumigation monitoring and may even6