Flowering dogwoods are frequently used ornamental trees in landscapes across America and are known for their attractive spring flower displays and bright autumn berries. Unfortunately, dogwoods are also highly susceptible to diseases ranging from mild, purely aesthetic illnesses to lethal funguses. Know the symptoms of these diseases so you can take steps to eliminate them when they appear.
This disease is caused by the fungus Elsinoe corni and affects the leaves and young shoots of flowering dogwood trees, according to the North Carolina State University College of Agriculture and Life Sciences website. Common in early spring, spot anthracnose forms tiny reddish purple spots that spread rapidly and destroy the leaves. Infected leaves become disfigured and eventually fall prematurely. Spot anthracnose can also affect the berries of flowering dogwood trees.
Septoria Leaf Spot
The fungus Septoria cornicola is responsible for this flowering dogwood disease, which attacks the leaves and becomes most severe during mid- to late summer. The disease can become severe earlier in the season, depending on spring weather conditions. Purple spots form on the dogwood’s leaves, disfiguring and discoloring them to the point that they fall off prematurely. These spots are larger than those caused by spot anthracnose.
This disease is common in trees planted in poorly drained soils and among newly transplanted trees with damaged roots. Caused by the Phytophthora cactorum, crown cankers appear as sunken, damaged areas that "may eventually girdle the stem and kill the top of the tree," according to the North Carolina State University College of Agriculture and Life Sciences. Prevent crown cankers by treating your dogwood with metalaxyl every two to three months.
Discula causes this highly destructive and common dogwood disease. Dogwood anthracnose resembles many foliage diseases at first, forming purple spots on the leaves. The disease soon spreads to the twigs and in some cases the trunk, causing elliptical brown cankers. Dogwood anthracnose is lethal if left untreated. This disease is particularly common in cool, moist environments and spreads more easily in forests than in landscaped areas. The frequent use of fungicides is recommended to prevent this disease.