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Pest: Major Pests |
Dogwood Anthracnose
Introduction
Tan disease spots on leaves.
credit: fs.fed.us
Dogwood anthracnose is a disease of flowering dogwoods caused by the fungus Discula destructiva. It was first reported in the northern United States about 25 years ago and has been slowly moving south. The origin is unknown at this time as forest managers are unsure if the fungus was introduced or a change in environmental conditions may have given this fungus the right conditions to become a significant forest health issue.
Current Situation
In Tennessee, dogwood anthracnose is most active in higher (3000 to 5000 feet) elevations and has been estimated to have killed 50% of the flowering dogwoods in the eastern half of the state. Middle and West Tennessee regions tend to be warmer and drier therefore have not been affected as much. It appears that the dogwood anthracnose has recently stabilized but it remains a high priority for monitoring.
Annual Survey
Disease spots on petals.
credit: forestpest.org
No formal survey for dogwood anthracnose exists in Tennessee. Forestry personnel are trained to recognized signs and symptoms of the disease and work with forest landowners to educate them on ways to maintain their dogwoods and make sound decisions regarding tree selection and planting sites.
Identification
Dogwood anthracnose first appears on the leaves of the lower crown as tan spots with purple rims. It is important not to confuse these tan spots with spots caused by Elsinoe corni or Septoria cornicola or other foliage disease. The dogwood anthracnose symptoms will gradually progress up the tree to the upper crown as the fungus spreads to the twigs and trunk, causing brown elliptical cankers. Leaves that show the dogwood anthracnose spots will not fall off in the fall and often remain on the tree until spring. Often, epicormic sprouts will grow from the trunk and become infected as well. Multiple cankers can girdle the individual branches or kill the entire tree. Spores produced by the fungus are spread by rain, insects, or birds mainly in cool, moist weather.
Management Options
Canker under the bark.
credit: forestryimages.org
Keep dogwood trees healthy by providing water during periods of drought, create partially shade conditions, mulch around the trees to reduce water loss, and protect the tree from mechanical damage. Infected dogwood trees stand the best chance of surviving is the infection is caught early, before extensive dieback occurs. Fungicides are also available to aid in treating infections.
What Can You Do?
If you intend to add a dogwood to your landscape, do not transplant one from the forest. Only purchase dogwoods from a reputable nursery. Be sure to ask the nursery managers about dogwood anthracnose as a quality control measure. Keep existing dogwoods healthy by pruning trunk sprouts, mulch around the base, water during dry periods, and consistent monitoring. Learn to recognize what the signs and symptoms are of an infestation and immediately contact your county agent, professional forester, or the Division of Forestry at (615) 289-7373 for more information.
Publications
Other Resources
http://www.na.fs.fed.us/spfo/pubs/howtos/ht_dogwd/ht_dog.htm
http://www.dontmovefirewood.org/gallery-of-pests/dogwood-anthracnose-disease.html
