Identifying and Controlling Dogwood Anthracnose
Dogwood (discula) anthracnose is a disease that affects flowering dogwood trees. The disease has been reported in many states across the U.S., primarily those on the east and west coasts. The discula species is the culprit of anthracnose, and it favors damp, cool temperatures. Dogwood anthracnose can occur in any season, and it has a higher likelihood when drought and winter injury weaken the trees. If consecutive years of infestation take place, it can wipe out woodland and ornamental dogwood trees in a particular location. In the wild, this fungus disease is quite common and is responsible for killing off many dogwood trees. In the landscape however, we can do more to notice the signs of anthracnose and control its symptoms. What are the signs and symptoms of dogwood anthracnose? When a tree has been infected with discula anthracnose, the first part to be infested is the lower leaves. Dead spots start to form and are brown or tan with a purple margin. The leaves die and drop, and the fungus continues on its journey upward. As the disease progresses, cankers form on the twigs and trunk, and necrotic areas begin to discolor. The cankers cut off the water and nutrient supply, and the tissues begin to die off. Sometimes, this disease can be confused with spot anthracnose because new greens may sprout below the cankered area. Unfortunately, this new growth is very prone to infection and will most likely die off as well. Dogwood anthracnose is just as bad as it looks, and it affects all parts of the tree, including the leaves, twigs, branches, trunk and flowers. Not only is dogwood anthracnose severe but also it is somewhat common. Fortunately, you don’t have to wait until the dark spots appear on the leaves, twigs and branches before you start treatment. There are effective steps you can take to prevent this fungus and grow strong trees. How can dogwood anthracnose be prevented? Healthy plants are always far less susceptible to fungal diseases than trees that have been weakened from winter burn, mechanical injury, drought or other disease. So, one of the things you can do is to keep a healthy landscape. This starts with the basics, such as planting dogwood trees in the right location and following good maintenance practices, such as pruning and watering the tree as necessary. If there is a drought, be sure to water the trees. Adding a two or three inch layer of mulch over the root system can help lock in moisture and protect the trees from mechanical injury. Air circulation is also important, so select a place in the yard where the tree will receive plenty of sun and good air movement to help with dry foliage and infestations. Do not use sprinkers, but instead incorporate a drip hose when watering to avoid excessive moisture on the leaves, which may encourage fungal growth. Treatments for antracnose are preventative, but very effective. The timing for treatment is important, with the first one starting at budswell. An arborist who is also licensed in pest control should be consulted.