Small, purplish spots on the leaves and petal-like bracts of Flowering Dogwood or Kousa Dogwood indicates a spot anthracnose infection. 

Spot anthracnose, a fungal disease caused by Elsinoe corni, results in distorted flower buds that do not open, red-purple spotted flower bracts that may malform, and numerous, small spots on leaves. It is a common disease of Cornus florida, Flowering Dogwood, and Cornus kousa, Kousa Dogwood, but is largely cosmetic in its impact. Leaf and bract spots are tan with purplish borders and the centers may fall out creating a shot hole presentation. The disease is first noticed in spring during wet weather periods and may not occur in dryer years.

Spot anthracnose is a different disease with different symptoms than the far more destructive dogwood anthracnose disease that killed much of the New York and New England native dogwoods in the late 20th century.

Prevention and management of spot anthracnose are difficult because the infection survives on twigs and branches over the winter. Fungicide applications cannot reduce the infection once it is present. A fungicide program needs to occur before the disease initiates in spring and be repeated every 10 to 14 days until early summer and is rarely undertaken by homeowners. Nonetheless, some plant hygiene measures can help. Cleaning leaves from under the tree in fall, keeping air circulation in the leaf canopy, and avoiding watering the tree with a hose or sprinkler system that will wet the leaves are worthwhile precautions to reduce impact.

Find more about dogwood trees in the home landscape in our Guide to Dogwoods.

Courtesy of NYBG Plant Information Service