The plant disease you’re referring to, Sasha, is called Sudden Oak Death (SOD), and it has the potential to do some very bad things to the dominant hardwood that covers 18 million acres of the southern Appalachians. The sudden oak death pathogen comes from the Phytophthora genus-whose scientific name means “plant destroyer”- and it is one bad blight. One notorious member of the family is P. infestans, a.k.a. the potato blight that caused the Irish famine in the mid-19th century.

Sudden oak death is a fungus-like pathogen spread by water or infected soil or plant material. A tree can be infected for years, with persistent symptomatic bark cankers. Yet once the leaves begin to wilt and die, the tree succumbs rapidly. Signs of crown dieback signal end stage decline and imminent death. Hundreds of thousands of coastal live oaks, black oaks, and tanoaks in California and southern Oregon have died since the disease was first detected a decade ago. It was so new to scientists that it wasn’t identified until 1999. One disturbing aspect of the disease is that several plant species, mainly understory trees and shrubs, serve as carriers of the fungus. It sickens them with a less virulent form of the disease, but they can spread the spores to oaks, which are the terminal hosts. Some of the host species read like a Who’s Who of the Eastern understory: rhododendron, mountain laurel, witch hazel, and horse chestnut. Ornamental shrubs such as lilac and camellia are also among the nearly 60 host species that have so far been identified.As devastating as sudden oak death has been in the West, it was considered contained to a quarantine zone of 12 northern and central coastal California counties and part of one in southern Oregon. Then, last March, contaminated host plants were shipped from a large nursery in southern California. The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) quickly moved to extend the quarantine to the entire state. But its actions may have come too late.The nursery shipped infected camellias to more than 100 other nurseries and garden centers in 14 states, including North Carolina, Tennessee, Maryland, Virginia, Alabama, and Georgia. The USDA shifted $15.5 million in emergency funding to APHIS to track down the infected stock to each nursery and set up a series of test plots in adjacent forested area to monitor their health.The great fear, of course, is that the pathogen has managed to move into the wild forest. Some of the nursery stock was sold during the affected time period and it could be anywhere. So far, none of the APHIS test plots have tested positive. But the disease-which favors the moist, cool conditions found in the Appalachians-has forest and plant pathologists spooked. Not all of the 38 oak species native to the East would be affected. But those that are-species including northern red oak and chestnut oak-make up huge percentages of the Appalachian forest. The northern red oak can comprise 80 percent of the canopy in some areas, while the chestnut oak is a member of the white oak group, which includes highly valued and long-lived trees. If the pathogen escapes into the wild and manages to infect these and other species, the effect on the Appalachians and entire Eastern landscape could be transformative. It’s no wonder that comparisons to the chestnut blight and Dutch elm disease are now being mentioned in the same breath as sudden oak death.Still, no one knows just how the pathogen will affect trees in the East. And, so far, last year’s accidental introduction doesn’t mean that the disease is established. Vigilance, education, and maintaining a strict western quarantine remain the best defense against sudden oak death. California has given the world many wonderful things, but this is one export nobody wants. For more information, visit the USDA’s SOD home page: www.na.fs.fed.us/SOD.Naturalist William Cocke can be reached at wtc4q@virginia.edu.