Country: United States

Title: Chrysanthemum White Rust (Puccinia horiana P. Henn.)

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The United States Department of Agriculture (USDA) has confirmed the presence of Chrysanthemum White Rust (CWR), Puccinia horiana P. Henn., in nurseries and some residences in Pennsylvania, Delaware, Maryland, and New York. 

The Pennsylvania Department of Agriculture (PDA) collected and diagnosed a positive sample on September 17, 2004, from a nursery operation in Chester County, Pennsylvania.  USDA confirmed this diagnosis on September 22, 2004.  Approximately 4,000 plants have been destroyed at the positive Pennsylvania nursery.

 Upon the determination of the positive diagnosis, PDA provided the Delaware Department of Agriculture (DDA) trace forward information.   DDA then submitted

22 suspect specimens to USDA for identification which were all confirmed positive for CWR on September 24, 2004.  Five retail nurseries and four private properties in

New Castle County, Delaware, were determined to have infected mums. 

On September 24, 2004, the Maryland Department of Agriculture received a suspect CWR infected sample collected at a nursery located in Montgomery County.  The sample was received and confirmed positive by USDA on September 29, 2004. Approximately 1,000 field grown chrysanthemum plants of several varieties have been destroyed at the positive Maryland nursery.

On September 27, 2004, the New York State Department of Agriculture and Markets detected suspect CWR infected samples from two garden centers in Westchester County, New York. The samples were confirmed on October 5 by USDA and on October 12 by Cornell University at the Long Island Horticultural and Extension Center which is in the National Plant Diagnostic Network.  A total of 771 chrysanthemum plants has been destroyed from both infected garden centers.

So far, no connections have been established between the positive CWR finds in Delaware, Pennsylvania, New York and the infected nursery in Maryland.  Trace back and trace forward investigations are in progress, and the National CWR Management Plan for Exclusion and Eradication is being implemented. 

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.  CWR is established in Europe, Africa, Australia, Central America, and South America. 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.  If you wish more details on the Federal regulatory program, you may contact Staff Officer Dr. Ved Malik at (301) 734-6774.

Posted Date: Oct. 29, 2004, 9 a.m.