Characterization and Pathogenicity of Apple Black Rot Pathogens

Black rot is a major issue in Wisconsin apple orchards. The disease is caused by the fungal pathogen Diplodia seriata which can infect apple fruits, leaves, and branches. During the 2021 growing season, we discovered another Diplodia pathogen on apple trees that has not been previously reported on apple in Wisconsin. We are assessing the pathogenicity of the new Diplodia sp. on apple trees and fruits in comparison to Diplodia seriata, the black rot pathogen. The outcome of this work will be a first report of this disease in Wisconsin and a better understanding of the threat of the novel Diplodia sp. to apple orchards.