Resistant Cedars May Be Answer To Root Rot Fungus After 44 Years Of Searching, Seeds Of Success Sown

Forty-four years ago, Lewis Roth began looking along streams and bogs in the Siskiyou Mountains and Coast Range for Port Orford cedars that survived while all around them others died from a swimming fungus that attacked their roots.

Carrying on Roth’s work at Oregon State University, plant pathology Prof. Everett Hansen is now overseeing the breeding of seedlings at the Dorena Tree Improvement Center outside Cottage Grove that stand up to the scourge commonly known as Port Orford root rot.

In perhaps 10 more years - 54 years after Roth began his search - the U.S. Forest Service hopes to begin planting the descendants of these seedlings as silver bullets against the deadly march of Phytophthora lateralis (fi-TOP-tor-ah lat-er-AL-is), which attacks the most valuable tree in the West.

After testing “thousands upon thousands upon thousands” of trees, Hansen has identified about 200 that have varying degrees of resistance, but only five that really stand up to the fungus.

“Ah, 510015,” Hansen said fondly as he read the yellow tag on a spindly 4-year-old tree growing in a cold greenhouse at the tree improvement center. “This is one of our best trees. It’s off the Gasquet District of the Six Rivers National Forest,” in Northern California. “It looks kind of strange because it’s been treated with hormones a number of times,” to force it to produce seed at a young age.

Phytophthora lateralis first showed up in the Northwest in the 1920s, when it started killing Port Orford cedar grown for landscaping materials in Seattle nurseries, eventually wiping out a thriving industry. Nobody knows where it came from. Some theorize it hitchhiked from Asia in the roots of imported seedlings. Others think it was lying dormant in the Northwest and came to life.

The spore of the fungus likes water and has a little tail for swimming. It hitchhiked south in mud stuck to the wheels of cars and trucks. In 1952 it showed up in Mingus Park in Coos Bay, at the center of the Port Orford cedar’s range, which runs from southwestern Oregon into northwestern California.

“Three cedar trees started dying,” Hansen said. “They were full of bark beetles. Being high-value trees, they salvaged them quickly before the bark beetles spread, not realizing the real problem was root rot.”

Carrying mud laden with the spores, the logging equipment spread the fungus throughout the lowland forest around Coos Bay. From there it spread up and down the coast, wherever roads could take it.

It now infects 10 percent of the Port Orford cedar’s range on national forests, and perhaps more on private lands, said Don Goheen, plant pathologist for the U.S. Forest Service’s Southwest Oregon Insect and Disease Technical Center.

It wasn’t until the 1980s that the U.S. Forest Service realized the fungus was hitchhiking in mud on logging equipment. To stop the spread, the agency has closed off roads through Port Orford cedar areas and requires vehicles that go through infected areas to wash off the contaminated mud.

There appears to be little threat the fungus could totally wipe out Port Orford cedar, but these defensive measures haven’t stopped the spread, Goheen said.

Once it is brought into a drainage, the spores move downhill, following rivulets and creeks until they sense the chemicals given off by the roots of a Port Orford cedar. Like a dog tracking a scent, a spore swims until it touches a root, where it sends out a little tube that penetrates the cell walls and spreads through the inner bark, killing the fine roots.

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.

Roth started looking for resistant trees in 1952. People would tell him of seeing a single tree living in the midst of dead ones, and he would take a cutting and root it. Then he would dip the roots in water laden with the spores and plant it to see if the tree could survive.

But all his cuttings died.

After he retired, Roth learned that by keeping the trees in a warm greenhouse, he was making the environment too favorable for the fungus. Even resistant trees had no chance.

By keeping the trees in natural conditions, Hansen began finding ones that did not die right away. That was 1987. Even some of the trees Roth had first identified as failures proved to be successes.

Last year, the tree improvement center produced 26,000 seeds from resistant trees, but it is a long way from producing trees for replanting sites ravaged by the fungus.

Though the volume of Port Orford cedar cut each year is small, it is the most valuable tree on national forests in the West.

Port Orford cedar is most highly valued in Japan, where it stands in for the native Hinoki cedar for sushi bars and beams in traditional buildings. Monks will come to Oregon forests to choose a particular tree for a temple.

The 92.5 million board feet of Port Orford cedar logs shipped to Japan from Coos Bay in 1995 averaged $6,160.73 per thousand board feet, compared with $1,013.76 for Douglas fir, the next most valuable species.

“We have a lot more hope than we did awhile ago,” Goheen said of the prospects of stopping the spread of the fungus. “Without the resistant trees, the only way to deal with the disease is to keep it from getting into new areas. That has proven to be extremely difficult.”