Plant Doctors Help You Fight Destructive Dogwood Disease

ST. PAUL, MN--Are destructive diseases damaging your dogwood trees? In the southeastern states, dogwood anthracnose has caused the death of millions of flowering dogwoods over several million acres of forest during the past decade, according to plant doctors.

Dogwood specialists and the public are invited to attend the Dogwood Anthracnose Workshop, September 22-23 in Lexington, Kentucky. Leading US plant pathologists will meet to review successes and present new research strategies. In addition to dogwood anthracnose, the workshop will focus on other dogwood maladies, particularly the destructive powdery mildew outbreaks recently emerging in the United States.

If you can't make it to the conference, plant doctors offer these suggestions for maintaining dogwoods in good health:

Water the soil around the tree at ground level to minimize stress from drought. Keep the foliage dry.
Mulch around the plant to protect the tree from drought.
Monitor trees and remove dead and dying branches. Rake and remove fallen leaves to avoid spread of disease.
Remove suckers on the trunk. They can lead to infected areas called cankers.
Apply a fungicide containing the active ingredient chlorothalonil, mancozeb, thiophanate-methyl or propiconazole to protect against leaf infections if Discula anthracnose has been diagnosed and if the dogwood is a valuable specimen. Fungicides are best applied in the spring (three or four applications during leaf expansion.)

What causes dogwood anthracnose disease? A tiny little fungus named Discula causes the devastating disease, dogwood anthracnose. Pacific and flowering dogwood are susceptible. Cool, wet weather, especially in the spring and fall, favors disease development.

"Leaves on the lower part of the tree develop tan spots with purple margins. Large blotches may appear and veins and leaf margins turn brown," said Dr. John Hartman, organizer of the Dogwood Anthracnose Workshop, and a University of Kentucky plant pathologist who is a member of The American Phytopathological Society.

Pacific dogwood prematurely drops infected leaves in the spring. Flowering dogwood infections also develop on shoots, twigs, and branches, especially on the lower portion of the tree. Infected areas, called cankers, also may form on the trunk at the base of infected branches. A proliferation of succulent shoots may occur on the trunk and large limbs of infected trees.

For Dogwood Anthracnose Workshop details, contact Hartman at 606/257-5779. The American Phytopathological Society's 5,000 members specialize in plant health management in agricultural, urban and forest settings. For more information about APS, access the Society's home page on the Internet: <www.scisoc.org>

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