USDA cuts postentry quarantine time for mums

The postentry quarantine period has been reduced from six months to two months for imports of rooted and unrooted cuttings of chrysanthemums, Leucanthemella serotina and Nipponathemum nipponicum. The quarantine period was established to prevent the spread of chrysanthemum white rust caused by the fungus Puccinia horiana.

USDA-Animal and Plant Health Inspection Service Plant Protection and Quarantine Division evaluated the “available scientific literature” and found that two months was an “adequate amount of time for white rust to express” symptoms. Most of the available research concluded white rust symptoms typically appear between five to 14 days, depending on climatic conditions. Higher temperatures increase the latency period, but typically not more than 14 days, according to PPQ.

Control efforts against white rust in the United States are costly, according to USDA-APHIS. If white rust is detected, growers typically must destroy all plants within a 1-meter radius of any infected plant, treat the entire production site and implement a host-free period to prevent reintroduction of the rust.

After a white rust outbreak in California in 2006, the estimated cost per acre of implementing the host-free period was $54,594, according to APHIS.

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For more: Arnold Tschanz, Plant Protection and Quarantine, (301) 734-5306; www.aphis.usda.gov.