Dogwood Anthracnose

One of the important ways that we can avoid introducing new plant diseases into our country or into states is through inspections of plant material as it is being brought into the United States or being shipped into the state. The Missouri Department of Agriculture conducts inspections of greenhouse and nursery stock throughout the state to make sure they are free of diseases or insects not presently in Missouri. One of the diseases that they

Tan lesions, typical of dogwood anthracnose

are continually monitoring for is dogwood anthracnose on flowering dogwood, Cornus florida.

Dogwood anthracnose is a fungal disease that infects both the flowering dogwood and the Pacific dogwood (Cornus nuttalli). Its distribution has been primarily in the Eastern states and Pacific northwest. Some of you may recall this is the disease that wiped out almost all native dogwoods up and down the east coast in the mid-to late 1980’s. It is not known where the disease originated or exactly how it was introduced to the United States. The disease has slowly crept eastward over the years, presumably though the movement of infected plant material and is currently established in native populations of flowering dogwood as close as Tennessee.

In Missouri, although MDA inspectors have occasionally found infected nursery stock, in as far as we can tell there has been no transfer of the disease to the native stands of Cornus florida. When infected nursery stock is found, the plants are destroyed and the established dogwoods in the areas surrounding the nursery are surveyed for the disease.

Leaf symptoms often develop first on the lower branches. The fungus creates tan, circular spots, rimmed with purple. Leaves

Symptoms of leaf scorch

may also have dead veins and leaf margins and large dead areas. Cankers may also develop on branches, leading to twig dieback. The girdling cankers most often occur at leaf nodes. It is important to recognize these symptoms and have them checked out by a qualified lab.

Leaf scorch caused by droughty conditions, root dysfunction or insect borers is often a symptom that people commonly confuse with those of dogwood anthracnose. Leaf scorch starts at the edges of the leaves and progresses inward to the main vein. It does not start out as spots.

Two important and useful sources of information regarding this disease and other disease problems affecting dogwood can be found at the following Web sites:

http://www.na.fs.fed.us/spfo/pubs/howtos/ht_dogwd/ht_dog.htm http://fhpr8.srs.fs.fed.us/pubs/dogwood/r8-fr14/r8-fr14.htm

Laura Kabrick, Extension Assistant, Plant Diagnostic Clinic, UMC (573)882-3019