St. Paul, Minn. (January 20, 2004)—Imagine your special someone's face as they open a bouquet of roses covered with white, powdery mildew. Not exactly romantic. But gardeners and sweethearts alike should be reassured that plant pathologists have been working diligently to keep roses healthy, beautiful, and free from such unsightly conditions.
According to plant pathologists with the American Phytopathological Society (APS), a number of diseases threaten rose health. Various fungi cause notorious garden problems such as the dreaded black spot on leaves or powdery mildew, a disease that causes petals, flower stems, as well as leaves to show a white, powdery coating. Similarly, another fungus causes rose rust, a disease in which powdery pustules of reddish-brown spores form on the underside of leaves. Affecting flowers directly, Botrytis blight causes them to droop, turn black, and eventually become covered in a gray mold.
Viruses and bacteria also threaten rose health. One virus causes rose mosaic, a disease that produces yellow, irregular line patterns in leaves. Crown gall, in contrast, is a bacterial disease that creates overgrowths on the roots or lower parts of the stem.
To protect roses from these diseases, plant pathologists have developed numerous disease-fighting tools including biological controls, the use of living organisms to control diseases. "Plant pathologists have continued to work on rose diseases since the days of Cynthia Westcott, one of the first plant pathologists to specialize in combating the diseases that affect rose health," said Ken Horst, professor emeritus at Cornell University. "New control options are continually being researched by plant pathologists in order to increase the protection of roses from such harmful diseases and thus improve rose health. Moreover, some of these new control options are environmentally safe to use," he said.
For serious rose lovers, Horst's comprehensive reference book, Compendium of Rose Diseases and Pests, Second Edition,
is available at APS PRESS. The American Phytopathological Society (APS) is a nonprofit, professional scientific organization dedicated to the study and management of plant disease with 5,000 members worldwide.