Sudden Oak Death
DB: This is Earth and Sky – on a disease that’s devastating oak trees in the western U.S.
JB: One of the visible symptoms of Sudden Oak Death is a black ooze that bleeds from the bark of the tree. The foliage of infected trees often turns from green to brown in a few weeks. The end for infected oak trees comes quickly – and, so far, there’s no cure.
DB: Sudden Oak Death first showed up along the central California coast about a decade ago. Tanoaks, coast live oaks, and black oaks have been hardest hit by this bark disease. Tens of thousands of trees have died. The disease has spread from Big Sur to Mendocino in California, and scientists fear further spread.
JB: No one knows yet how to contain the disease, which spreads in mud and splashes of rain. The fungus that causes Sudden Oak Death is related to the species responsible for the Irish potato famine. Another version of this fungus, by the way, is also killing eucalyptus trees in Australia.
DB: For now, in some forested areas along the U.S. west coast, quarantines are in effect. People can help by not transporting plants out of infected areas – and by washing mud off their shoes after walking in place where the fungus might be lurking. That’s today’s show – was made possible by the National Fish and Wildlife Foundation, in cooperation with the U.S. Forest Service. We’re Block and Byrd for Earth and Sky.
The following individuals were interviewed for today’s show. Our thanks to:
Susan Frankel
Plant pathologist
United States Department of Agriculture Forest Service Pacific Southwest Region
David Rizzo
Associate professor of plant pathology
University of California, Davis
Web links to related information:
The California Oak Mortality Task Force
Marin County UCCE Sudden Oak Death
Author’s Notes:
Many fungi don’t cause disease. Instead, they benefit a forest by breaking down and recycling dead organic material such as logs and leaves. This transfers their nutrients back to the soil where they can be used by other trees. Some trees depend on fungi to help their roots absorb water and nutrients.
Before the Sudden Oak Dath fungus’s discovery in the U.S., it had been found only on rhododendron plants in Germany and the Netherlands. How the disease got to California remains a mystery. Because Sudden Oak Death is brand new, scientists still have a lot to figure out. Perhaps the biggest mystery is where the disease came from. One possibility is that the fungus hitchhiked on a European rhododendron plant, then escaped from a nursery. The disease may have also come from somewhere else where it exists but hasn’t yet been identified.
According to Susan Frankel, a Forest Service plant pathologist, “The pathagen does have limits – [it’s] limited to oak forests – only within 45 miles of the coast.”
It’s not just an oak problem. Madrone, buckeye, and huckleberry are among the 10 kinds of plants that have come down with Sudden Oak Death so far. Sudden Oak Death affects different species of plants in different ways. No one knows why some species are harder hit than others. “That is the 64,000 dollar question,” says UC Davis plant pathologist David Rizzo. Answering it might help scientists breed genetic resistance or impede the spread of the disease.
The species of Phytophthora that causes Sudden Oak Death received its own name just last week (first week of July, 2001). It’s now called Phytophthora remorum. Remorum means “little branches.”
Additional Teacher Resources
U.S. Forest Service, Six Rivers National Forest: Sudden Oak Death Frequently Asked Questions
A brief overview of the symptoms and implications of Sudden Oak Death in California.
Invasivespecies.gov, Species Profiles: Sudden Oak Death, Phytophthora ramorum
A great resource! This site provides several links to information, publications and organizations at the Federal, State, and International level concerning invasive plant species, including Sudden Oak Death.
U.S. Department of Agriculture, Agricultural Research Service: Sudden Oak Death: ARS Scientists Fight Back
Sudden Oak Death? a mostly mysterious disease? affects not only these majestic hardwoods but many other trees and shrubs, including backyard favorites like azaleas, camellias, and rhododendrons. This article gives more insight into this mysterious disease as well as the efforts being made by scientists to combat it.
