Spot Anthracnose on Dogwood
Dogwood tree buds are beginning to swell. These trees are a favorite herald of spring. The bracts come out before the leaves and are the real eye-catchers – white, pale pink, or sometimes reddish-pink, with small clusters of the true yellow flowers centered in the middle.
The Cornus florida or Flowering Dogwood is typically modest in size. Usually 15-25 feet tall and 4-6 inches in diameter it can sometimes grow to 40 ft tall and growth to a foot or more wide. The “flower” is recognized as the NC state flower and is a lower-canopy woodland tree found throughout our state. Historically, Cornus florida was used to produce ink and scarlet dye and the hard, dense wood was valued for mallets and tool handles. Tannins found in parts of the tree were harvested for medicinal uses.
While it prefers organically rich, moist, acidic, well-draining soils in part shade it can be grown in average soil in sun as long as the roots are kept protected, cool and moist since their shallow root systems make them susceptible to leaf scorch during long droughts. Unfortunately, drought is not the only concern for these beauties. They are preyed upon by a number of insect pests as well as deer, they don’t handle pollution problems and are susceptible to fungal pathogens as well. Spot anthracnose (Elsinoe corni) is a common problem and control of this disease is hard to achieve.
1 Spot anthracnose on dogwood (Cornus sp) PDIC
2 Leaf spot anthracnose on Dogwood by Steve Pettis, Jr
What to look for? Cool, wet weather. Check. In the coming months, scout for tiny spots with reddish, purplish borders and tan centers on the bracts and leaves of dogwood trees. The disease is most severe when we have high rainfall amounts as the flower buds are opening and as the leaf buds are opening. The fungus also survives in the shoots and on the fruit. In the spring when we get more rainfall we get the disease symptoms. But no rainfall means very little of this disease and you can manage moisture levels at the shallow root levels with irrigation and mulch. With high rainfall amounts look for problems and if you had it last year, keep scouting for it this year as it survives in the shoots. Rake up fallen leaves and debris regardless as a precaution to remove sporulation sites and other pest hideaways. Fungicide spraying every 7-14 days from flower bud break to complete leaf expansion is a management technique, but If you have more than one or 2 specimen trees to get all the extra attention – it’s not very practical.
A sound practice in any garden is to choose plants with disease resistance in the first place. In the ornamental nursery industry many varieties have been hybridized for this characteristic as well as other desirable traits. From ‘Cherokee Sunset’ to ‘Weaver’s White’ there are many choices available.
Despite the potential for spot anthracnose, the flowering dogwood is a lovely addition to a shade garden. From the heraldic bright colors of spring, to cool green summer shade, flaming oranges, and red autumn leaf colors, and distinctive geometric bark in winter, there is always something to enjoy. To view a list of cultivars and varieties that are disease resistant, as well as other good-to-know information about this plant, take a look at Cornus Florida.
Minda Daughtry is the Horticulture Agent for North Carolina Cooperative Extension in Lee County.