Cercospora beticola tolerant to triphenyltin hydroxide

Abstract

Three of five sugarbeet fields from two districts in Minnesota had unacceptable levels of Cercospora leaf spot after being treated with the maximum label amount of triphenyltin hydroxide (TPTH) in 1994. Strains of the fungus with varied levels of tolerance to TPTH were recovered from leaf spots. Mancozeb was effective against the tolerant strains. Strains with resistance to thiophanate methyl also were recovered.