Flowering dogwood (Cornus florida
) and the Kousa dogwood (Cornus kousa
). The fungus is killing tree-type dogwoods in the wild. In the landscape, the disease can be kept in check with fungicides.
Lower leaves on the tree are the first to be infected. Necrotic (dead) spots are tan to brown with a purplish margin. Leaves die and drop early. Cankers form on twigs and trunk during the spring and fall. Necrotic areas on the twig and trunk discolor. The cankers girdle the twigs and trunk thus cutting off water and nutrients to plant parts beyond the cankered areas. The cut off tissue then dies. It is common for new shoots to sprout below the cankered area on the trunk. These new shoots are very prone to infection. This disease may be confused with spot anthracnose
) and Septoria; both of which affect dogwood and are mainly cosmetic.
If rainy weather persists during flowering, the pathogen is known to infect the "flower" (white bracts).
To help reduce infection and increase the plant's resistance, keep plants healthy. Plant the trees in the right location. Then follow good cultural practices during planting, maintenance and pruning of these trees. Effective fungicidal control must be started before there is any major dieback. Prune out and destroy infected branches. Removing and destroying infected leaves may have a limited benefit. Removing the water sprouts helps to reduce trunk cankers. Use recommended fungicides according to directions.