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Home > What's New > Chrysanthemum White Rust

Chrysanthemum White Rust, Puccinia horiana, Found in Pennsylvania

September 27, 2006

chrysanthemum white rustOn September 15, 2006, during a routine Cooperative Agricultural Pest Survey (CAPS), a Pennsylvania Department of Agriculture (PDA) inspector detected Chrysanthemum White Rust (CWR) symptoms in seven potted Chrysanthemum plants out of a lot of 302 Chrysanthemums at a large national retailer in Pittsburgh. This detection was confirmed by Plant Protection and Quarantine (PPQ) as Chrysanthemum White Rust, caused by the obligate fungus, Puccinia horiana P. Henn. PDA has issued a stop sale order and PPQ issued an Emergency Action Notification (EAN) to prevent sale of infected plants.

These infected potted plants were from a farming operation in Lehigh County, Pennsylvania, where CWR was discovered in a single block at one end of a ten acre field. The National CWR Management Plan for Exclusion and Eradication is being implemented. The plan includes destruction of infected plants and those within one meter, spraying remaining plants three times with an approved systemic fungicide, and monitoring the plants for symptoms. There are several greenhouses and a three acre field that are physically isolated from the infested field that have been inspected and found to be apparently free of CWR. The plants in the three-acre field were sprayed with myclobutanil as a precaution, and then released.

CWR was also confirmed in Chrysanthemums located in the garden center of a second national retailer in Pennsylvania. Trace forward and trace backward activities are being expedited to determine the full extent of exposure of Chrysanthemums in the United States, especially because this is the peak season for Chrysanthemum sales.

CWR, caused by the fungus Puccinia horiana P. Henn., is a quarantine pest for the United States. The importation of CWR host plants is prohibited from infested countries and regions due to the potential of this organism to be transported with the host plants. When CWR is found in the United States, the States and PPQ cooperate to eradicate it. Disposal of infected plants and weekly fungicide sprays of myclobutanil are required to manage this disease as outlined in the CWR Management Plan for Exclusion and Eradication. Additional information on CWR may be found at the PPQ website, http://www.aphis.usda.gov/ppq/ispm/cwr/index.html.