Chrysanthemum White Rust
Monday, 01 October 2007 13:54
Chrysanthemum white rust (Puccinia horiana) was confirmed for the first time in Connecticut on September 12, 2007 in Fairfield and Hartford Counties. Infected plants were found in nurseries and garden centers during visual inspections by Connecticut Agricultural Experiment Station staff. The disease was confirmed by Sharon Douglas from the Experiment Station and a USDA APHIS PPQ laboratory. As of October 16, 2007, plants that have tested positive for chrysanthemum white rust (CWR) include several 'Gretchen'™ cultivars ('Bold', 'Flashy', and 'Sunny'), as well as the cultivars 'Dark Veria'™ 'Debonair',™ 'Ashley',™ 'Vicki',™ 'Okra',™ 'Cesaro',™ and 'Flamingo Pink'™ , 'Gold Finch Yellow' , 'Canelli' and 'Galatino' that are not in the 'Gretchen'™ series. In addition, cultivars not specified tested positive in a wide range of colors and types (some of which were grass-mum combination pots). Although CWR has occasionally been reported in the U.S. and Canada, all previous outbreaks were successfully eradicated. CWR is a regulated pest of quarantine significance, and steps are being taken by state and federal regulators to remove and destroy infected plants from the two confirmed sites in compliance with the CWR Eradication Protocol established by the USDA APHIS-PPQ. Additional inspections are underway at nurseries and garden centers in Connecticut.
Chrysanthemum white rust infects 12 species of chrysanthemum, including garden mums, pot mums, and Nippon daisies. The disease was first found in Japan and China more than 100 years ago, and has since become established in Europe, South America, Central America, Africa, Australia and parts of Asia. Infected plants may not show any symptoms during hot or dry conditions but when the weather turns cool and wet, symptoms develop. Symptoms of CWR on infected plants are quite distinctive and include raised pink or white, waxy pustules on the underside of the leaf. Chlorotic spots develop on the upper leaf surface that may become sunken and necrotic. Severely infected leaves dry up and persist on the stems. Severe outbreaks of CWR may result in total crop loss.
Additional information is available via the following links:
USDA - APHIS - Plant Health, Plant Protection and Quarantine
USDA, ARS Systemic Botany and Mycology Laboratory
British Columbia Ministry of Agriculture Food and Fisheries
Photos: Chrysanthemum White Rust, 2, 3
Sharon M. Douglas, Ph.D.
Plant Pathologist
Head, Department of Plant Pathology & Ecology
The Connecticut Agricultural Experiment Station
Donna Ellis
Extension Educator and State Survey Coordinator,
USDA APHIS Cooperative Agricultural Pest Survey (CAPS) Program
University of Connecticut
