In Poland, the first description of the causal agent of the valdensia leaf blight fungus Valdensinia heterodoxawas on highbush blueberry in 2011. Our study identified this pathogen in highbush blueberry plantations and on bilberry plants to describe its biology, molecular characteristics, and disease epidemiology. The 115 fun-gus isolates yielded were divided into 2 groups based on the colony morphology differences on PDA (potato dextrose agar) medium. For the isolates from each group, morphology and growth dynamics were studied on PDA and WOA (weak oatmeal agar) with added highbush blueberry/bilberry/lily of the valley leaf decoction under different light and temperature conditions. The isolates’ colony morphology differences were noted depending on the medium type. The best isolate growth was at 20 °C/19 °C-day, 12 °C-night, with a 12-hour photoperiod. Isolate identification using PCR showed nearly 100% nucleotide sequence similarity to refer-ence isolates. On infected leaves, the release height of conidia was 18 cm. The presented results are novel in Poland and have a broader-than-domestic significance.