Evaluation of Dogwood and Birch Species and Cultivars for Resistance to Key Insect Pests and Diseases

Abstract Ten cultivars of dogwoods (Cornus spp.) were evaluated in multi-year trials for relative reisistance to the dogwood borer, Synanthedon scitula (Harris); cold injury; canker disease, Botryosphaeria dothidea; spot anthracnose, Elsinoe corni; and powdery mildew, Oidium sp., Microsphaera sp., and Phyllactinia sp. Similarly, eight cultivars of birch (Betula spp.) were evaluated for resistance to the birch leafminer, Fenusa pusilla (Lepeletier); Japanese beetle, Popillia japonica Newman; aphids, Hamamelistes spinosus Shimer; the bronze birch borer, Agrilus anxius Gory; and leaf-spot, Cryptocline betularum. All cultivars of C. florida, C. kousa and C. kousa x florida were susceptible to dogwood borer, although the C. florida cultivars were surviving better than the others. Cornus mas and C. kousa cultivars were relatively resistant to powdery mildew while C. florida x kousa hybrids and C. florida ‘Cherokee Brave’ were intermediately resistant. Betula platyphylla szechuanica ‘Purpurea’ was highly suscept...