Sudden Oak Death Detected in Pennsylvania

On Feb. 18, 2010 the Penn State Plant Disease Clinic received a sample of Laurus nobilis (actual sample photographed at left), known commonly as bay laurel, true laurel, sweet bay, laurel tree, Grecian laurel, or bay tree. The tips of the leaves submitted were dead or dying and it was reported by the grower that 95% of well rooted plants in 12 or so flats exhibited the symptoms. The United States Department of Agriculture-Animal Plant Health Inspection Service (USDA-APHIS) confirmed the plants to be infected with Phytophthora ramorum, the Sudden Oak Death pathogen known to occur in trees and shrubs on the west coast of the U.S. and in Europe. Phytophthora ramorum can infect many important ornamental trees and shrubs under the right conditions. There is a great deal of concern that this fungus-like organism could cause significant economic damage to eastern forests and landscapes if not excluded from the region.

The’ bay laurel’ submitted was not Umbelluiaria californica, the California bay or California bay laurel that grows on the west coast and is a major host of Phytophthora ramorum that then spreads to oaks. However, Laurus nobilis is known to be a host of Ph. ramorum.

SO WHAT YOU SAY!!
Phytophthora ramorum has, to date, been excluded from the eastern U.S. but this occurrence may indicate that the plant pathogen is now or will soon be in the region from multiple sources. In 2009, Laurus nobilis was named as the Herb of the Year by the International Herb Association (IHA). Laurus nobilis seed can be purchased from a number of sources including through Amazon.com. Web information indicates that the seed is difficult to germinate. It is my understanding that people have been encouraged to grow this plant and that it has been used in various Master Gardener projects. If seed or tissue associated with seed is actually the source of the pathogen, it is possible that Phytophthora ramorum has arrived in the east with seed purchased by backyard gardeners, etc. Where is the ‘failed to germinate’ material discarded? Where are plants with dying leaf tips discarded?

"It is VERY important to note that the P. ramorum was detected on a plant growing in a GREENHOUSE. There is NO EVIDENCE that Phytophthora ramorum is anywhere in the east outside that greenhouse. Certainly there is NO EVIDENCE THAT IT IS IN THE GENERAL ENVIRONMENT OR FOREST in the east. The reason for releasing the info was to remind us that P. ramorum COULD be brought to the east on plant material. The growing of Laurus by gardeners is being encouraged. Let's hope Laurus is not actually an important source of P. ramorum." Dr. Gary Morman, Professor of Plant Pathology, Penn State University