Chrysanthemum white rust found in Delaware on Oct. 4, 2007
Chrysanthemum white rust caused by the fungus Puccinia horiana affects cultivated chrysanthemum plants in the Family Asteraceae. The disease is not established in U.S. chrysanthemum production, and could have significant impact on both greenhouse and outdoor plants of chrysanthemum, as well as cut flowers. The disease has occasionally been found in United States nursery stock in greenhouses, but it is easily and quickly cleaned up when found. Symptoms include yellow spots on the upper surface of the leaves that are up to 5 mm in size. On the underside of the leaves, raised bumps or pustules develop which have a waxy, warty appearance and are light in color. If you see signs of white rust on leaves or flowers of a plant purchased recently in Delaware, please take it to your nearest County Extension Office or contact the Delaware Department of Agriculture. Plants should be destroyed.
From Nancy Gregory, Plant Diagnostician, Department of Plant & Soil Sciences, University of Delaware