Cedar trees begin recovery from fungus infestation
Once, the Port Orford cedar was the most prized tree in the Northwest woods.For Americans, it made stadium seats, boats and outdoor furniture that would not rot. From the Japanese, it fetched high prices for use in sushi bars.It is was prized, too, as an ornamental, its feathery fronds ranging from gold to blue.Then in the 1920s, a fungus-algae mix known as root rot began to kill the trees. For decades it has seemed an impossible dream that it could be defeated.But in the past 10 years, university and government researchers have begun to produce trees that are practically immune, offering hope for a new nursery stock and stands in the wild.Next year, Monrovia Growers in Dayton, Ore., will start selling an ornamental variety grafted to rootstock that resists the disease in the Portland, Ore., and Seattle areas.Everett Hansen, professor of plant pathology at Oregon State University, said he knew of no other campaign against a tree-killer that has achieved so much success so quickly.But he warns that the battle is not over. The disease could easily mutate to a form that attacks even the resistant trees.Root rot – Phytophthora lateralis – is a close relative of the sudden oak death pathogen that has wiped out oak stands in Northern California and southwestern Oregon. It likely hitched a ride on a ship from Asia, although no one knows for sure how it arrived in Seattle.It spread through the Northwest on mud attached to cars and trucks.In most trees, the fungus can spread through the whole root system to the base of the trunk, blocking the flow of nutrients. But the resistant trees are able to stop the spread to varying degrees.”It’s almost an immune response,” said Hansen. “It’s about as close as a plant comes to that kind of a response.”Samples of some 12,000 trees found surviving amid stands that succumbed to the disease were brought in for testing, and about 100 were found with varying resistance, said U.S. Forest Service geneticist Richard Sniezko at the Dorena Genetic Resource Center outside Cottage Grove, Ore.Port Orford cedar is particularly suited to the quick development of resistant strains because it can be rooted from cuttings as well as grown from seed, and young trees can be forced to produce seed within just three years, Sniezko said.Monrovia is relying on one genetic type for root stock, grafting other varieties onto it. But for planting in the wild the Forest Service and BLM needed a range of genetic types, said Sniezko.That way if the disease mutates, more trees are likely to survive. It also provides trees that can grow at a variety of sites with different altitude, rainfall and soil type.The first seed produced in 2002 was put out in test plots, and is doing well, said Sniezko.Some seedlings are being planted to restore creeksides burned by the Biscuit Fire on the Siskiyou National Forest, but widescale planting is hampered because there is far less logging going on, so far fewer places to reforest, Hansen said.Nurseries had been afraid to grow Port Orford cedar because of the disease problems, but Monrovia started working with seven resistant trees from OSU about five years ago, and chose one to use as root stock for grafting some of the old varieties, said conifer grower Ron Kinney.Next year the company plans to offer about 1,000 of a variety called Silber Star, which has a bluish foliage, and more varieties will follow in coming years, he said.
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