Sudden oak death affecting rhododendrons, Douglas fir

In an effort to stop the spread of disease from California nurseries, the Washington State Department of Agriculture joined almost a dozen other states in placing a quarantine on nursery stock from California.

The emergency quarantine is in response to the spread of sudden oak death from infected nursery stock from California. Sudden oak death is a new, invasive disease affecting about 60 species of woody plants, including camellias, rhododendrons, evergreen huckleberries and Douglas fir.

The disease is caused by the fungal-like organism, Phytophthora ramorum. Sudden oak death is not a food safety concern.

"I undertake this measure with great reluctance," said Valoria Loveland, WSDA director. "However, we must protect the natural environment of the state and maintain the trust and confidence of our trading partners. We need to ensure our nursery, forest and agricultural industries remain economically sound."

Phytophthora ramorum was recently found in nursery stock imported from at least two southern California locations.

The emergency rule requires susceptible species of nursery plants from California to be inspected and issued a certificate confirming they are free of Phytophthora ramorum before they leave their state of origin. The rule also requires that a copy of the certificate must be sent to WSDA offices prior to shipment.

WSDA implemented precautionary measures almost a month ago to try and prevent the disease from spreading to Washington nurseries. The agency issued an emergency order requiring nurseries to notify WSDA of all incoming shipments of woody plants and shrubs from anywhere outside the state. This would allow WSDA staff to inspect and test suspect stock before it enters the market.

Through both of these measures WSDA hopes to prevent any further infestations and to identify and eradicate the disease wherever it has entered the state.

Common symptoms of sudden oak death are withered and blackened leaves and stems. However, WSDA staff and nursery associations point out that these symptoms are also symptoms of many other diseases.

"The fact a plant in Washington has a leaf or stem that is withered or black doesn't mean it has sudden oak death," said Tom Wessels, WSDA's plant services program manager. "Over the last year and a half, we've tested more than 21,000 samples and less than one percent have been positive for the disease."

Phytophthora ramorum has never been found in Washington outside a nursery.