Susceptibility of Cornus Species to Two Genera of Powdery Mildew

Abstract Powdery mildew disease severity was assessed in fourteen species of Cornus. Seedlings of C. alternifolia, C. controversa and C. mas were not infected with powdery mildew. One cultivar of C. alba, ‘Bud's Yellow’, was also not infected, whereas ‘Ivory Halo’ was parasitized with Phyllactinia guttata. Cultivars of C. florida (‘Cherokee Brave’, ‘Cloud 9’, and ‘Cherokee Sunset’) and lines of C. kousa (seedlings and clones of C. kousa var. chinensis) significantly differed in their susceptibility to powdery mildew. All trees of C. florida and C. kousa had thalli and cleistothecia of Erysiphe pulchra on abaxial and adaxial surfaces. Location of mycelia and cleistothecia of P. guttata on leaves were variable for blue berry dogwood species.