Strategy and industry approach to managing the QoI resistance challenge

Resistance management (RM) issues are handled through volunteer compliance of guidelines developed within the Fungicide Resistance Action Committee (FRAC) and the NA-FRAC QoI Working Group. Representatives from companies that are either developing or maintaining registrations for QoI fungicides write specific guidelines for each crop. Factors considered when proposing guidelines are: theoretical measure of resistance risk, propensity for resistance based on models and or history of resistance development by the pathogen, spectrum of activity and the chemical/physical properties of the compounds, number and timing of fungicide sprays commonly used on a crop, and projected cost of the products. Examples of the interaction of these factors are found in sugar beets where at planting and foliar applications target different pathogens, peanuts where guidelines differ based on the projected number of sprays, and potatoes where product mixtures are common. Guidelines must be simple, clear, concise, and easy to apply in real life situations or they will not be utilized by growers. RM issues yet to be resolved include the role of government in writing and enforcing RM, expanding guidelines to specialty crops, and adoption of guidelines by generic producers when a chemical class is no longer covered by patents.