Susceptibility of Cultivars and Hybrids of Kousa Dogwood to Dogwood Anthracnose and Powdery Mildew
Thomas G. Ranney, Larry F. Grand, and John L. Knighten
Abstract: Twenty taxa of dogwood including cultivars of kousa dogwood (Cornus kousa) and cultivars of hybrids between flowering (Cornus florida) and kousa dogwoods were evaluated for susceptibility to dogwood anthracnose (Discula destructiva) and powdery mildew (Microsphaerapulchra). Trees were grown under the canopy of a native stand of flowering dogwood that was infected with both diseases and were also inoculated artificially with spores of D. destructiva. None of the taxa were found to be immune to dogwood anthracnose, yet there was considerable variation in resistance to the disease. Cornus kousa 'Steeple', a clone of C. kousa 'Milky Way', C. x Stardust®, C. x Stellar Pink®, and C. x Celestial™ were found to be resistant to dogwood anthracnose as indicated by < 1 % of total leaf area affected, 100% survival through the following spring, and no detection of D. destructiva in woody tissue. The C. kousa cultivars 'Wolf Eyes', 'Moonbeam', and 'Autumn Rose' and seedlings of C. florida were highly susceptible with 100% of the total leaf area affected and 100% mortality by the following spring. The other taxa were intermediate in susceptibility to D. destructiva. Only five of the taxa: C. kousa 'Elizabeth Lustgarten' and 'Steeple' and the hybrids C. x Stardust®, C. x Constellation®, and C. x Ruth Ellen® were infected by M. pulchra.