Fighting Chrysanthemum White Rust

The American Nursery & Landscape Association (ANLA) and the Society of American Florists (SAF) recently released an excellent Powerpoint presentation for growers and sellers concerned about Chrysanthemum White Rust (Puccinia horiana, "CWR"). CWR is a rust fungus that is able to infect twelve different chrysanthemum species, including pot mums, cut mums and garden mums. It can cause serious economic damage, and is currently considered a pathogen of quarantine significance in both the USA and Canada.

Over the past thirty years, there have been several outbreaks of CWR across North America, including in Massachusetts, but these local outbreaks have always been eradicated. The threat remains, however, and it is extremely important to detect this pathogen early in order to minimize economic losses.

If you grow or sell mums, please take a few moments to view the Powerpoint presentation to learn how to recognize the symptoms of Chrysanthemum White Rust infection. Early detection, and a rapid response if CWR is found, are two important steps in preventing the establishment of this pathogen.

Because this is a pathogen of quarantine significance, anyone who detects the presence of CWR is required to inform the USDA, state or county officials. If you think you see signs of Chrysanthemum White Rust, you can let the Massachusetts Department of Agricultural Resources know through our Pest Reporting form, or call our Pest Hotline (617-626-1779).

(Source: ANLA and SAF press release. Photo of CWR courtesy of the Central Science Laboratory, Harpenden Archive, Bugwood.org)