|TREES MAY ESCAPE DISEASE|
|January 22, 2002 12:00 am|
The jury is still out on what Sudden Oak Death disease may do to redwood trees, said Oregon Department of Forestry Forest Health Monitoring Specialist Mike McWilliams.
He told members of the Brookings-Harbor Garden Club Monday that a good scientist may have jumped the gun a bit when he told the media that redwoods may be a host species for Phytophthora ramorum, a fungus-like disease.
McWilliams said the disease organism was found in water on some wilting redwood sprouts, but that doesnt necessarily mean it was responsible for the condition of those sprouts.
He said hes seen infected tanoaks among redwood groves in California, and the disease didnt appear to be affecting the redwoods.
He said he would be surprised if the disease could kill healthy adult redwood trees, but even if it could kill only sprouts it would affect redwood reproduction.
I dont think it would wipe out the coastal redwoods, said McWilliams, but were not putting anything past this fungus. Its had us scratching our heads from day one.
After touring infected sights near Brookings again Tuesday, he said he changed his theory about three times on how the disease migrates and what it affects.
On Monday, McWilliams was leaning toward a theory that birds, possibly fantailed pigeons, may have carried the disease to the Brookings area from the San Francisco Bay area.
In Oregon, the disease has been confirmed only near Brookings, mostly along Joe Hall and Mayfield creeks. Those areas are under a quarantine.
McWilliams said eradication efforts appear to have been successful in Oregon, so far.
As in California, Sudden Oak Death killed tanoaks near Brookings. McWilliams said it has also damaged leaf-tips in rhododendrons and branches in evergreen huckleberry plants, though it has not killed those species in Curry County.
No infected myrtlewood trees have been found in Oregon, though the disease has damaged, but not killed, some in California.
It has not affected azaleas, but McWilliams said he will keep an eye on Azalea Park, since it is so close to areas infected by the puzzling disease.
He said Sudden Oak Death disease was identified in the Bay Area in 1995, though it had probably been killing oaks since 1993.
It was first discovered killing large black oaks in private neighborhoods. Because beetles moved into the dying trees, they were thought to be suffering from a beetle infestation problem.
By 2000, an unknown phytophthora was identified as the agent killing the oaks. It was similar, but not identical, to one found in Germany and The Netherlands since 1993.
In 2001, it was named Phytophthora ramorum by the Germans, though no one knows where the disease originated.
The organism is called a fungus, but one of the three types of spores in it has flagella and can swim.
McWilliams said that makes it more like an animal or a red algae. He said it can be blown about in the wind, and splashed onto hosts by rain.
Its a very flexible organism, said McWilliams, which makes it very scary.
He said the disease is not native to either the United States or Europe. It infects parts of plants above the ground, not the roots.
It is spread by rain-splash and wind, and can be transported in soil and plant material. No one, however, knows how the disease skipped from the Bay Area to Brookings.
It was discovered near Brookings in July 2001 by McWilliams and Ellen Goheen, of the U.S. Forest Service.
Aerial surveys revealed patches of dying tanoaks and ground surveys confirmed the sites near Brookings were suffering from Sudden Oak Death.
McWilliams said cultures of the fungus can be successfully grown only half the time, but DNA tests can positively identify the organism.
A year ago, Sudden Oak Death was found only near the Bay Area, and only affected various species of oaks.
Then it was found on rhododendron, myrtlewood, evergreen huckleberry, madrone, big-leaf maple, viburnum, buckeye, manzanita, California honeysuckle and coffeeberry. It affects the leaves and branches of those species, but doesnt kill them.
McWilliams said red oak and pin oaks are also susceptible, which concerns people on the East Coast.
The disease blackens rhododendron leaves, similar to sunburn, but with a more diffuse margin between healthy and dead tissue.
It hasnt affected myrtles in Oregon, but has caused minor leaf-tip dieback in California.
If the disease is found on leaves, McWilliams recommends removing and burning them. Do not, he said, put infected leaves in the compost.
The disease causes cankers on the branches of evergreen huckleberry, but mainly in the crown of the plant. He said many things can cause similar symptoms. The disease would have to be confirmed with DNA analysis.
The disease has been identified in 10 counties in California. The northernmost site is 100 miles south of Oregon.
The Brookings sites are under quarantine, which means movement in and out is restricted.
Log trucks coming out of the areas must be washed, and host material is not allowed to be moved out.
McWilliams said the disease was also found recently on the south bank of the Chetco River, across from the confluence with Joe Hall Creek.
He said another unknown phytophthora was discovered killing a small patch of tanoak two-tenths of a mile across the California border.
Surveys conducted in December did not find the disease in Oregon outside of the nine infected sites near Brookings. McWilliams believes the disease has been in Oregon about two years.
Discrete patches of diseased trees suggest point introductions of the pathogen, said McWilliams.
Some infested areas are remote, others are near roads, trails and logging. There is no obvious link to human activity.
McWilliams and other officials met with key landowners and worked out an eradication plan.
The infested areas were delineated, with a 100-foot buffer zone. Landowners have already cut and piled all host material on eight of the nine sites.
The material has been burned on two sites, and will be burned on the rest when conditions permit. The sites will continue to be monitored.
McWilliams said no chemical treatments have yet been found to be effective.
He said the eradication effort may have been successful because the disease was discovered early in Oregon, the infected areas were small and heat appears to kill the pathogen.
He said California is too far gone for eradication to stop the disease. He said they are more worried about dead trees falling on houses there.
In the future, said McWilliams, the forestry department and forest service will continue to survey areas adjacent to infected sites, monitor the treated areas, resample other sites and conduct aerial surveys.
He advised garden club members to not buy rhododendrons grown in Bay area nurseries.
Its a very bad idea to buy plants from infested areas, he said.
He also advised members to be careful with plants they bring to the annual sale in May. If grown near an infested site, he said, use common sense and watch for symptoms.