Kousa Dogwood Research Articles

Susceptibility of Cultivars of Several Dogwood Taxa to Powdery Mildew and Spot Anthracnose

Abstract Incidence of powdery mildew (Microsphaera penicillata) and spot anthracnose (Elsinoe corni) was assessed on 37 selections or cultivars of flowering dogwood (Cornus florida), kousa dogwood (C. kousa), hybrid dogwood (C. kousa x florida and C. nuttallii x florida) and giant dogwood (C. controversa). Across all cultivars, the flowering dogwood and C. nuttallii x florida ‘Eddie's White Wonder’ are more susceptible to powdery mildew and spot anthracnose than the kousa, C. kousa x florida hybrids and giant dogwood. Among the cultivars of flowering dogwood screened, ‘Cherokee Brave’, ‘Cherokee Chief’, ‘Welch's Bay Beauty’ and ‘Weaver's White’ were partially to highly resistant to both diseases. With few exceptions, the kousa dogwood and C. kousa x florida hybrids, and giant dogwood suffered very little powdery mildew or spot anthracnose-related damage.

Resistance to Dogwood Anthracnose among Cornus Species

Dogwood anthracnose caused by Discula destructiva poses a threat to flowering {Cornus florida) and Chinese (C. kousa) dogwood in the eastern United States and to Pacific or western dogwood (C. nutallii) in the Pacific Northwest. Differences exist in the impact the pathogen has on these hosts (subjectively in the order C. florida > C. kousa and C. nutallii). Ten Cornus species, including C. alternifolia, C. amomum, C. controversa, C. alba, C. augustata, C. florida, C. kousa, C. mas, C. sericea, and C. stolonifera, were evaluated for disease reaction in 1991 and 1992 at locations in eastern Tennessee infested with D. destructiva. Greatest disease severity in 1991 was observed on C. controversa, C. florida, C. kousa cv 'Chinensis', and C. sericea. In 1992, C. florida, C. sericea, C. kousa cv 'Chinensis', C. alba, and C. stolonifera cultivars appeared susceptible to anthracnose. Symptoms developing on each appeared similar to those observed on flowering dogwood, and D. destructiva was successfully isolated from lesions within the canopy of the trees. Other Cornus species tested, including an unnamed Chinese dogwood cultivar, appeared resistant. The results of this study indicate that concerns regarding the anthracnose susceptibility of native and ornamental Cornus species may be raised. Finally, the possibility should be considered that infected Cornus species (other than C. florida) might serve as a mechanism for the introduction of D. destructiva into anthracnosefree areas of the United States.

Susceptibility of Cultivars and Hybrids of Kousa Dogwood to Dogwood Anthracnose and Powdery Mildew

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.

Field Evidence for Kousa Dogwood Resistance to Anthracnose Caused by Discula sp.

Field Evidence for Kousa Dogwood Resistance to Anthracnose Caused by Discula sp.

Field Evidence Confirms Cornus Kousa Dogwood's Resistance to Anthracnose

In a moisture regime very favorable for leaf disease infections (an overhead irrigation system), Cornus Kousa trees were infected by the anthracnose fungus (Discula sp.) and some died. In an adjacent comparable area, but with no overhead irrigation, C. florida trees were infected and dying but trees of C. kousa that touched them remained healthy...as is usual with that species.