First Report on Quinone Outside Inhibitor Resistance of <i>Alternaria alternata</i> Causing Alternaria Brown Spot in Tangerines in São Paulo, Brazil

Abstract

Field resistance to quinone outside inhibitor (QoI) fungicides in Alternaria alternata causing Alternaria brown spot of mandarins was reported by growers in Brazil in 2017. Conidial germination tests were performed, and isolates showed effective concentration to inhibit 50% of conidia germination (EC 50 ) to be over 100 ppm. This is the first report of QoI resistance in A. alternata causing Alternaria brown spot in the state of São Paulo, Brazil.