DOGWOOD ANTHRACNOSE
Dogwood anthracnose, caused by the fungus Elsinoe corni, occurs in states bordering the Atlantic Ocean and has also been reported in Louisiana. Its primary host is flowering dogwood, Cornus florida L.
Leaf and flower symptoms of dogwood anthracnose.
Anthracnose occurs in the spring and affects not only the leaves, but also the buds and “flowers”. The buds may fail to open or they may produce stunted flowers. These have many circular to elongated spots with light tan centers. Margins of these spots are purple to brown. Often the flowers abort before development. Foliage spots (1-2 mm. in diameter) are raised at the margins. They are purple at the edges and yellow-gray in the center. Later centers of spots may fall out causing a “shothole” effect. Dozens of spots may be present on a single leaf and may be scattered or concentrated at tip, margin, or midrib. Twisting and malformation of the leaves are common. In addition to floral and foliage spots, infected areas may also occur on petioles, stems, and fruit clusters. All three areas have spots similar to those on the foliage.
Other diseases which may be confused with anthracnose include Septoria and Ascochyta leaf spots. Septoria usually begins around July and unlike anthracnose has more angular lesions that are between the veins. Ascochyta spots may be larger (6 mm. in diameter) than anthracnose, and tissue discoloration may extend outside of their borders. Occasionally the leaves may totally blacken. This disease may occur as early as June.
Wet, humid weather at certain stages of plant development is required for infection. Homeowners may obtain effective control by removing and burning infected plant parts. Various fungicide sprays are recommended by authors of ornamental handbooks.