| Pest Alert: Chrysanthemum
white rust found in PA nursery (October 14, 2004)
Chrysanthemum white rust was confirmed on approximately
800 field grown chrysanthemums at a nursery in Chester
County, Pennsylvania on September 17, 2004. As a result
of a trace forward survey 22 plants with chrysanthemum
white rust were found in Delaware.
Chrysanthemum white rust (Puccinia horiana)
is a serious fungal disease of chrysanthemum. White
rust can spread quickly in greenhouse and nursery
environments causing severe crop losses. Chrysanthemum
white rust was first discovered in Japan in 1895 and
was confined to China and Japan until the 1960s. Today
it is established in Europe, Africa, Australia, Central
America, South America, and the Far East. In the last
25 years localized introductions of chrysanthemum
white rust have occurred within the United States
or Canada and have subsequently been eradicated or
are being eradicated. Last year CWR was reported in
one location in Norfolk County, Massachusetts. The
MA DAR worked with the nursery to eliminate the disease
from their facilities and surveyed the surrounding
area to insure the rust had not spread. CWR is a quarantine
significant pest in the United States; therefore,
occurrence of this disease leads to state and federal
regulatory action.
Hosts
Twelve species of chrysanthemum (Dendranthema
spp.) are susceptible including pot mums, spray mums,
and garden mums. Other hosts include Nippon daisy
(Nipponicanthemum nipponicum) and High daisy,
and Ajania pacifica. Resistant species include annual
chrysanthemum (C. carinatum), crown chrysanthemum
(C. coronarium), pyrethrum (Tanacetum
coccineum), marguerite daisy (Argyanthemum
frutescens), ox-eye daisy (Leucanthemum vulgare),
shasta daisy (Leucanthemum X superbum),
and corn marigold (C. segetum)
Symptoms
The symptoms of chrysanthemum white rust are very
distinct. 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. Raised
beige to pink pustules form on the underside of leaves
beneath the spots. Pustules become white with age.
Pustules are most common on young leaves and flower
bracts but may form on any green tissue or the petals.
Symptoms usually occur during cool, wet weather.
The pest alert is from the Massachusetts Introduced
Pests Outreach Project, a collaborative project between
the Massachusetts Department of Agricultural Resources
and the UMass Extension Agriculture and Landscape
Program aimed at preventing the establishment of new
pathogens and pests in Massachusetts. Visit the project
website (http://www.massnrc.org/pests)
for more information on Chrysanthemum
White Rust and other emerging pests or to subscribe
and unsubscribe for pest alerts.
|
