The occurrence of Blumeriella jaapii resistant forms to dodine and benzimidazole fungicides in selected orchards in central Poland

Abstract

Cherry leaf spot (Blumeriella jaapii) is the most dangerous disease of orchards and nurseries of stone fruit trees, especially sour cherries. Chemical method is the primary tool for controlling cherry leaf spot. Dodine, benzimidazole and triazole fungicides are the most commonly used. The frequent application of these fungicide groups resulted in the development of resistant forms of the causal agent to their active substances. In years 2012–2015 in 33 selected sour cherry orchards located in central Poland, the occurrence of resistant forms of B. jaapii to dodine and benzimidazoles was determined by using a spore germination test on the poisoned agar medium. The study showed high resistance to thiophanate-methyl in 15 orchards, and to dodine in 5 orchards. The medium resistance to thiophanate-methyl and dodine occurred in 7 orchards. Low level of resistant forms to thiophanate-methyl was found in 11 orchards, and to dodine – in 21. The obtained results will be the basis for implementation of cherry leaf spot control programs in regard to appropriate antiresistance guidelines.