Introduced Pests Outreach Project

Chrysanthemum White Rust

Pathogen Alert: CWR detected in Massachusetts (September 26, 2008)

(Click on an image below to see the captioned full-size version)
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Scientific Name: Puccinia horiana
Common Names: Chrysanthemum white rust

Known Hosts:
12 species of chrysanthemum are suspectible including pot mums, spray mums, and garden mums (Dendranthema X grandiflorum = Chrysanthemum morifolium).
Other hosts include Nippon daisy (Nipponicanthemum nipponicum = C. nipponicum), High daisy, and C. pacificum = Ajania pacifica

Light green to yellow spots up to 5mm in diameter appear on the upper surface of the leaf. These spots become brown and necrotic with age. (Figure 1)
Raised beige to pink pustules form on the underside of leaves beneath the spots. Pustules become whiter with age.
(Figures 2 and 3)
Pustules most common on young leaves and flower bracts but may form on any green tissue or the petals. (Figure 4)
Severely infected leaves wilt and will eventually dry up completely.
Similar Disease or Symptoms
Brown rust of chrysanthemum Chocolate brown pustules are found on both sides of the leaves. See this page for more information:

Fact sheets and references:
Printable Chrysanthemum white rust pathogen alert (pdf)

Fact Sheet on CWR from UMass Extension

Cooperative Agricultural Pest Survey Chrysanthemum White Rust
Survey maps for U.S. and links to further resources

USDA/APHIS Chrysanthemum White Rust Web page
National management plan contains strategies for eradication of CWR and information on its biology

Chrysanthemum White Rust: Systematic Botany and Mycology Lab of USDA Agricultural Research Service: Good photos of symptoms

CWR Page from British Columbia Ministry of Agriculture, Food, and Fisheries

last reviewed December 30, 2014

Massachusetts Department of Agricultural Resources
Massachusetts Introduced Pests Outreach Project is a collaboration between the Massachusetts Dept. of Agricultural Resources and the UMass Extension Agriculture and Landscape Program. This website was made possible, in part, by a Cooperative Agreement from the United States Department of Agriculture's Animal and Plant Health Inspection Service (APHIS). It may not necessarily express APHIS' views.