Since the late 1970s, many flowering dogwoods have been infected by Dogwood anthracnose. Diseased trees have been found in localized areas, but more commonly, landscape trees are affected. Dogwood anthracnose is a deadly fungal infection that within two to three years can kill a large flowering dogwood tree. Once identified it is imperative that the landowner hire a tree removal service to come in and trim branches to remove infected areas or if necessary to remove the entire tree.
The first sign that a tree has been infected are small brown spots on the leaves and flower bracts that usually appear in May or June. Spores from these areas of infection can be washed onto new leaf tissues during irrigation or heavy rain. Unchecked, these spots can grow into large brown areas that may have a purple edge. Within a short period, the disease progresses to twigs and then to the main branches and finally the trunk. Once the disease has reached the larger limbs, the trunk cankers develop. Cankers ultimately kill the tree.
The first step to prevention is to keep your trees as healthy as possible. Trees that are well-maintained and inspected by a tree service will have a better chance of avoiding or surviving infection. During times of drought, keep the trees watered but do not use an overhead watering system as this can spread the disease. Mulch should be put down four inches from the tree base out to the drip line which can help maintain moisture levels and avoid mower injury. Use a fertilizer in the late spring or early summer that is low in nitrogen and high in phosphorus. The nitrogen content is very important because increase nitrogen levels have been shown to increase the susceptibility for anthracnose. When deciding on tree placement, look for an area that receives full sun and has adequate drainage. Do not use transplanted forested trees; instead look for disease-resistant varieties of flowering dogwood. Proper pruning and raking of fallen leaves will help curb the spread of the disease.
Once the dogwood anthracnose has been identified, it is necessary to control the spread of the disease. Wait until winter and prune back limbs that have cankers present. Trim all the way back to healthy growth. To avoid the spread of disease, pruning must be done under dry conditions. Between pruning cuts it is necessary to clean pruners with bleach or alcohol. Be very cautious during the removal of cut limbs. Make sure that leaves do not fall on the ground and do not burn the limbs. Fungicides can also help control outbreaks. There are many available on the market. Consult with an experienced tree service and they can recommend treatments that will help reduce the spread of dogwood anthracnose.
Dogwood anthracnose is a disease that when left untreated can rapidly infect other dogwoods and in a short period of time can kill even larger trees. Proper identification by a knowledgeable tree service agent and aggressive treatment are necessary to ensure the continued health of your flowering dogwood. Every spring the flowering season of the dogwood is highly anticipated for its beauty as well as the remarkable color changes during the fall. It is well worth the effort to protect these beautiful trees.