Friday, August 7, 2009

Greenhouse and Nursery - Chrysanthemum White Rust

Chrysanthemum White Rust has been found in Delaware. The following is more information.


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, and could have significant impact on chrysanthemum production. Therefore, the pathogen, P. horiana, is a USDA/APHIS reportable pathogen. The disease has occasionally been found in Delaware, but in cooperation with USDA and Delaware Department of Agriculture, it has been easily detected and eradicated. It has recently been determined that the fungus may survive over the winter season in infected plantings of hardy mums. 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 symptoms of white rust on a plant purchased or in established plantings in Delaware, please take it to your nearest County Extension Office, the UD Plant Diagnostic Clinic, or contact DDA, Bureau of Plant Industry. Plants should be destroyed.

Chrysanthemum White Rust. Photo from the Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services,

Information from, Nancy Gregory, Plant Diagnostician, UD

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