An Asian fungus that attacks oaks trees, rhododendrons, mountain laurel and related species is the newest threat on the horizon for Western North Carolina ecosystems, according to plant pathologists and foresters.

For the past seven years the fungus, known as Sudden Oak Death, has been moving up the Pacific Coast, killing stands of oak trees and shrubs in its path. Three weeks ago, the fungus escaped from California in a nursery shipment from Monrovia Nursery, one of the largest plant suppliers in the nation. Shipments of potentially infected material went to 39 states. Plant pathologists hope to track down and test every plant shipped from the nursery not only the week of the outbreak, but for the past 12 months. Unfortunately, contaminated shrubs or trees could well be planted in people’s backyards by now, said Steve Oak with the United State Forest Service in Asheville.

“We should be very concerned,” said Oak. “This is exactly what we have been trying to guard against.”

Ecologists fear the fungus, known as Phytophthora Ramorum, could take the same toll on oak and rhododendron species as the Chestnut blight did to the American Chestnut in the early 1900s. The Chestnut blight was also an Asian fungus. Just 30 years after being introduced in the U.S., every Chestnut tree on the eastern seaboard was dead

“The genus Phytophthora is a nasty, nasty fungus,” said Robert Bruck, a North Carolina State University plant pathologist.

Should the fungus land in Western North Carolina, Sudden Oak Death could have devastating consequences for Appalachian forests.

“We’ve been aware that Sudden Oak Death could arrive here at any time for several years now,” said Christine Johnson, supervisory forester with the Great Smoky Mountains National Park. “We have all been wanting a quarantine on plant material coming out of California.”

When the shipment of contaminated nursery stock occurred three weeks ago, the states of Georgia, Tennessee and Florida enacted quarantines on all nursery shipments from California. North Carolina has not done so. Nursery stock shipments in the 1900s through the 1920s were the primary culprit in spreading the Chestnut blight.

The fungus can potentially spread through contaminated soil picked up on hiker’s boots, mountain bike tires, or tent poles, Johnson said. Visitors to state and national parks in California and Oregon are given explicit instructions on cleaning all outdoor gear to prevent the spread. Parks with known infected areas, such as Muir Woods, home to the giant sequoias, have set up wash stations.

Bob Miller, spokesman for the Great Smoky Mountains National Park, said the impacts on wildlife could be potentially devastating.

“Oaks filled much of the void in terms of mast production for wildlife after the chestnut died,” Miller said. “One reason deer and turkey and bear populations have rebounded in the past 20 years or so is that large oak trees have finally filled in the missing niche left in the forest by chestnuts.”

Aiding and abetting

The Phytophthora escape was first detected three weeks ago on a contaminated Camellia shrub shipped out of Monrovia Nursery. Once discovered, all new shipments from Monrovia were halted, but nurseries scattered across 39 states had already received batches of potentially infected plant material that week alone.

Plant pathologists are systematically testing those shipments to determine whether infected stock arrived in their state, according to Oak with the U.S. Forest Service in Asheville.

So far, infected material made it to three nurseries in Florida and in at least one other state that officials have not yet identified, said Oak. Some states discovered no contaminated stock among Monrovia shipments, while others have not yet finished the complex testing regimen.

“Information on this changes daily. Even less than that. New information is being revealed all the time,” said Oak. Oak, a leading expert in the new and emerging field surrounding Sudden Oak Death, is working around the clock as part of a national team formulating strategies for tracking, identifying and containment of fungus.

The biggest concern is not the recent batch of shipments, however, as those have been successfully quarantined for testing. The bigger fear is that Monrovia has been shipping infected material for some time, as a plant can carry the fungus without showing immediate signs, Oak said.

“We know that species grown in the same lots as plants that were infected were shipped,” Oak said.

Monrovia is legally obliged to provide plant officials with the past 12 months of shipment records. But retail garden centers could have long since sold the Monrovia stock.

“We just don’t know what’s going on yet,” Oak said. “We don’t have a good detection strategy to track individual sales from somebody’s nursery.”

In addition, Monrovia is not sharing information on shipments made more than 12 months ago. Oak said a plant shipped out in February 2003 could have been grown in the same lot as the known contaminated species, but the destination of those plants will never be known.

Sales made that long ago might be a lost cause anyway, as tracking within the wholesale sector stops with the retail trade. Tracking every plant to its final destination would be impossible, according to Bill Skelton, a horticulture specialist with the North Carolina Cooperative Extension.

“It would be very difficult to have that degree of tracking established in the industry,” said Skelton.

Spotting Phytophthora

The best-case scenario is that all infected plant material shipped out of Monrovia is found and destroyed, Oak said.

“The worst scenario is it’s confirmed positive in several nurseries and it is possible that infected stock has gone into people’s backyards and from there slopped over into the natural forest,” Oak said.

If that happened, a massive public information campaign — akin to a product recall — would have to be launched to help homeowners determine if they had infected plants.

“It would be dependent on everybody who ever bought a Monrovia plant in the past two years a) knowing it was from Monrovia, and b) participating in it,” Oak said.

Signs of Phytophthora are brown spots on leaves ranging from the size of a dime to a quarter to the whole leaf, eventually leading to foliage loss. Of course, ambiguous brown spots are the symptoms of numerous plant diseases, including over watering, and are not always of consequence.

“There’s that game of 20 questions you have to play all at the same time. Just because a leaf has spots on it doesn’t indicate by any means that it’s Sudden Oak Death,” said Bill Skelton, a horticulture specialist with the North Carolina Cooperative Extension in Waynesville.

Further, a plant can be a host to Phytophthora, spreading large quantities of spores into the ecosystem, without showing any signs of the disease itself. Skelton said when in doubt, he would advise nursery owners to quarantine suspicious plants and send a leaf sample off for testing.

“It is a potentially very damaging situation. From a North Carolina perspective, everybody is just watching it really, really close. We’re doing everything we can to restrict its movement and minimize its spread,” Skelton said.

There is no protocol established yet for homeowners who purchased a Monrovia plant known to be host of Phytophthora in the past year. But there is one factor working in WNC’s favor, according to Craig Artley, the owner of Grass Roots Nursery in Waynesville.

The infected Monrovia nursery is in Southern California, where climates are much warmer, Artley said.

“Southern California is not a comparable growing area to ours. We get our products out of the Oregon nursery or local areas. We feel that we’re clean,” Artley said.

Artley, an experienced nursery man, cautions against an alarmist view.

“Disease and insect problems are every day functions,” Artley said.

He said the protocol in place to halt the spread of the pathogens worked in this case — the escape was discovered, tracked and destroyed.

“Everything that’s shipped should be inspected. If it’s inspected and certified, you shouldn’t be getting any infected material.”

Last year, Oak, along with NCSU researchers, surveyed nurseries in North Carolina and six other states.

“We processed over 10,000 leaf samples and they came up all negative,” Oak said.

As there are many funguses within the Phytophthora family, the only way to positively identify the fungus is a molecular DNA test.

“There’s no dip stick you can put in the soil and it comes up red and you know you have trouble. It’s a very elegant testing system,” Oak said.

A national Sudden Oak Death hotline has been set-up at 888.703.4457.

Fungus factoids

The fungus first turned up in 1996 in forests of Southern California. Stands of 30 to 40 oak trees would go from healthy to dead in about three months.

“Foresters were really stumped as to why these trees were dying,” Bruck said. The mystery disease was called Sudden Oak Death. It was another five years before Berkley researcher Mike Rizzo pinpointed the cause of the disease to be an Asian fungus.

“This is the same story we keep living over and over again,” Bruck said.

Native dogwoods across the South are being annihilated by an Asiatic fungus. Same with the beech bark disease and with elms.

“The list goes on and on and on,” Bruck said.

In Oregon, foresters are attempting to isolate and burn the infected stands.

“Absolute destruction of trees, roots and soils around the infected area might — and the key word is might — be able to control this disease,” Bruck said. Similar tactics were taken with the chestnut blight, a fungus also in Phytophthora family, but they were unsuccessful.

Oak said that is because the blight had already reached a “critical mass.”

“It was too late. It was already too established. It was already into the power curve,” Oak said.

Oak spent last week examining infected stands in Oregon and experimenting with containment methods. Researchers are still unclear exactly how the fungus spreads. With the chestnut blight, spores of the fungus were transported on the fur, feathers and feet of animals that came in contact with infected material. The spores were also spread through the air on wind-driven rain.

“How aggressive is this oak pathogen going to be? We don’t know. The jury is out on Phytophthora Ramorum,” Bruck said.

Researchers first thought the fungus preferred cooler, wetter weather, according to Mike Benson, who is also an NCSU plant pathologist. Western North Carolina was pegged as an ideal climate for the fungus, while the warmer regions of the south, including the North Carolina Piedmont and more southerly states, did not have as much to worry about.

But now, the fungus has been discovered in one area of Oregon that has 100-degree temperatures in the summer and single digit humidity levels.

Oak said it would be “total speculation” to peg the fungus to a climate at this point. Isolated contaminations also have been documented in the United Kingdom and the Netherlands.

Plant politics

Without the assistance from humans, the fungus could feasibly eventually spread to the eastern seaboard, Bruck said.

“There are oak trees from one side of the country to the other,” Bruck said.

But that’s not the biggest fear for ecologists.

“At this point, it is the human assisted spread we need to be careful of,” Oak said.

Ecologist and plant pathologists believe the government should be more aggressive in combating this pathogen.

In the meantime, Oak recommends those doing spring landscaping buy as many plants as possible that have been locally grown. This means not only supporting the more mom-and-pop nursery businesses, but also asking them where their stock came from.

“There’s no reason why we can’t grow all our own nursery stock in North Carolina,” Oak said. Indeed, the nursery business is the fastest-growing sector of agriculture in North Carolina and ranks third in the Western North Carolina agricultural economy. But, large-scale nurseries like Monrovia can produce huge quantities of plants with an economy of scale, Oak said. However, this does not account for the huge risk and cost that will be born by taxpayers over the Phytophthora scare, let alone a Phytophthora outbreak, Oak said.

Oak wants a total lock down on all plant shipments across state lines.

In fact, it’s too risky not to, said Bruck.

“What are the costs of annihilating the oak population of the United States? It is unthinkable,” Bruck said. “No one comes for tourism if there’s dead trees. When two people come down with SARS, everybody goes berserk. But when it comes to plants ...”