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POSTERS: Fungicide and antibiotic resistance

A closer look into fungicide resistance: How does application rate affect the development of SDHI resistance?
Katrin Ayer - Cornell University. Kerik Cox- Cornell University

Fungicide resistance is problematic in plant pathogens where management relies heavily on the use of fungicides. Resistance development often results in a lack of effective management and henceforth crop loss. With the advent of next generation succinate dehydrogenase inhibitors (SDHIs), it is essential to incorporate sustainable resistant management practices to prevent future loss of this fungicide class. To understand programs that best reduce resistance risk in the field, the effect of fungicide application rate on the development of resistance was tested in three pathosystems with a history of resistance: Venturia inaequalis, the causal agent of apple scab on apple, Stemphylium vesicarium, the causal agent of Stemphylium blight on onion, and Botrytis cinerea, the causal agent of gray mold on grapes. Selection was carried out through repeated fungicide applications of high or low rates of the following SDHI fungicides: fluxapyroxad, fluopyram, and benzovindiflupyr. After selection, fungicide sensitivity was tested via in vitro growth inhibition assays. Current results in apple and onion suggest use of lower application rates may result in an increased frequency of isolates with reduced sensitivity. Further, these outcomes support that managing overall populations size may be the first step in managing fungicide resistance emergence. Sensitivity testing and selection with B. cinerea on grape is currently ongoing.