Chrysanthemum White Rust
Pathogen Alert: CWR detected in Massachusetts (September 26, 2008)
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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
Symptoms |
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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) |
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Raised beige to pink pustules form on the underside of leaves beneath the spots. Pustules become whiter with age.
(Figures 2 and 3) |
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Pustules most common on young leaves and flower bracts but may form on any green tissue or the petals. (Figure 4) |
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Severely infected leaves wilt and will eventually dry up completely. |
Similar Disease or Symptoms |
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Brown rust of chrysanthemum Chocolate brown pustules are found on both sides of the leaves. See this page for images |
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 page
USDA/APHIS Chrysanthemum White Rust Web page
Chrysanthemum White Rust: Systematic Botany and Mycology Lab of USDA Agricultural Research Service
last reviewed February 18, 2021 |