Chrysanthemum White Rust

(Click on an image below to see the captioned full-size version)
Figure 1		Figure 2		Figure 3		Figure 4

Scientific Name: Puccinia horiana
Common Names: Chrysanthemum white rust, CWR

Known Hosts: Twelve species of chrysanthemum are known to be susceptible to CWR, including:
	pot mums, spray mums, and garden mums (Dendranthema X grandiflorum, syn. Chrysanthemum morifolium)
	Nippon daisy (Nipponicanthemum nipponicum, syn. C. nipponicum)
	High daisy (Leucanthemella serotina, syn. C. serotinum)
	C. pacificum (syn. Ajania pacifica)

Symptoms
	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 more white 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 the bulletin from Yodor Bros. for pictures and further description:
http://www.ceris.purdue.edu/napis/pests/cwr/cwryod1.html

Notes: The following species are considered resistant to CWR:
	annual chrysanthemum (C. carinatum)
	crown chrysanthemum (C. coronarium)
	pyrethrum (Tanacetum coccineum, syn. C. coccineum)
	marguerite daisy (Argyanthemum frutescens)
	ox-eye daisy (Leucanthemum vulgare)
	shasta daisy (Leucanthemum X superbum, syn. C. maximum)
	corn marigold (C. segetum)

Fact sheets and references:
Chrysanthemum white rust fact sheet (pdf)

Cooperative Agricultural Pest Survey Chrysanthemum White Rust
Survey maps for U.S. and links to further resources
http://www.ceris.purdue.edu/napis/pests/cwr/index.html

USDA/APHIS Chrysanthemum White Rust Web page
National management plan contains strategies for eradication of CWR and information on its biology
http://www.aphis.usda.gov/plant_health/plant_pest_info/cwr/index.shtml

Chyrysanthemum White Rust article from UMass Extension Floral Notes
September-October 2004,Vol. 17, No. 2, pp. 5-6.
http://massnrc.org/pests/linkeddocuments/Chrysanthemum%20white%20rust_article.doc

Chrysanthemum White Rust: Systematic Botany and Mycology Lab of USDA Agricultural Research Service (Nice photos of symptoms)
http://nt.ars-grin.gov/taxadescriptions/factsheets/index.cfm?thisapp=pucciniahoriana

Two web pages about CWR are available from Canadian sources:
British Columbia Ministry of Agriculture, Food, and Fisheries
http://www.agf.gov.bc.ca/cropprot/cwrust.htm

Canadian Food and Health Inspection Service
http://www.inspection.gc.ca/english/sci/surv/data/puchore.shtml

Chrysanthemum White Rust: Phytosanitary Alert System: North American Plant Protection Organization
http://www.pestalert.org/Detail.CFM?recordID=18

last reviewed April 9, 2008