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Posted 19 February 2007. PMN Crop News.

A Bouquet of Canker Doesn’t Say I Love You

American Phytopathological Society.

St. Paul, Minnesota (February 1, 2007) – Would a wilted rose covered in cankers smell as sweet as a healthy rose? Maybe, but giving the love of your life a bouquet of canker for Valentine’s Day most likely won’t convey a message of love.


According to plant pathologists with The American Phytopathological Society (APS), a number of diseases threaten rose health and cause unsightly conditions such as cankers and wilting. Various fungi cause 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. 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.

To get roses in your garden ready for spring, APS plant pathologists recommend:

• Pruning and destroying diseased shoots and flowers

• For soil-borne diseases, i.e. crown gall, removing soil from around infected plant roots to assure galls and infected roots are discarded before planting in the same area

• Looking for protective sprays that will control foliar and flower diseases (powdery mildew and Botrytis) that are effective and are environmentally safe

• Raking and destroying fallen leaves from around rose bushes during and at the end of each growing season to avoid continued spread and over-wintering of disease.

For additional information on how to keep roses healthy and disease-free all year long, check out the Compendium of Rose Diseases, available from APS PRESS, at

The American Phytopathological Society (APS) is a non-profit, professional scientific organization. The research of the organization’s 5,000 worldwide members advances the understanding of the science of plant pathology and its application to plant health.

Amy Steigman
American Phytopathological Society