NORTHERN NUT GROWERS ASSOCIATION, INC.

A Stricken Tanoak

Tanoaks have been dying in California. Scientists call the disease that is killing them "sudden oak death syndrome". This syndrome was first seen five years ago in a small patch of tanoak trees near San Francisco. Since then, the syndrome has attacked three tree species and has spread over 350 miles along the California coast. There are concerns that the disease might spread to other species and into other states.

Researchers became increasingly concerned when a group of scientists discovered that the syndrome appeared to be a previously unknown species of Phytophthora, funguslike organisms that include the species that caused the potato blight in Ireland and the species that are presently killing oak trees in Europe and eucalyptus trees in Austrailia.

Symptoms

The first symptom of the syndrome is bleeding--red sap oozes from the bark. Later the tree is attacked by beetles that leave a coating of sawdust on the bark, and by fungi that sprout black wartlike growths on the trunk. Leaves change from green to brown very quickly.

How The Disease Is Spread

Researchers are not sure of how the disease spreads, but plant pathologists at the University of California at Davis discovered that the new Phytophthora makes a spore than can swim. This finding suggests that the disease could move in water. The disease can also have spores that move via soil, wind, hiking shoes, beetle feet or tires. It is possible that humans are spreading the disease after visiting and infected area.

According to scientists, the spores that cause the disease are likely to spread outside of California. However, they will only cause problems if tree species in the new areas are susceptible and if the Phytophthora can withstand a variety of climates. Researchers are testing both conditions.

Since this article has been written, there have been new developments relating to the cause of the disease. These have been posted on our news page. Click here to transfer to the news page.

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