Dozens of headlines this week have claimed that a humble mold is threatening to ruin Christmas. CBS News and the Associated Press reported that phytophthora root disease is killing Christmas trees across the country.
However, contrary to the reports, experts in Oregon, the nation’s top Christmas tree producer, say the threat posed by root rot is relatively small.
Root rot is a tree disease caused by a variety of water molds, which produce swimming spores that can spread through poorly drained soil.
An aggressive species of phytophthora mold is a serious problem for Christmas tree farmers who grow Frasier firs in North Carolina, and a native species of phytophthora mold does affect some noble firs in the Northwest.
Gary Chastener, a tree disease expert at Washington State University, says most Christmas tree farmers in Oregon have been able to manage the disease without major losses by planting Douglas firs and other disease-resistant evergreens in wetter areas.
Furthermore, Chastagner says an estimate cited by the Associated Press and CBS news that phytophthora root rot could cost the Christmas tree and nursery industry $304 million a year actually refers to the potential cost of the spread of an entirely different tree disease: sudden oak death.
“That figure that’s being reported of $300 million has nothing to do with phytophthora root rot in Christmas tree plantations,” Chastagner says.
Chastanger says reporters appear to have mixed up their phytophthora molds, confusing Phytophthora ramorum, the pathogen that causes sudden oak death, with the native phytophthora molds that infect some fir species in Oregon.
“The fact of the matter is, phytophthora ramorum has never been found in a Christmas tree planting. It’s an exotic phytophthora species that there is a federal quarantine on,” he says.
Phytophthora is the name of a genus of water molds. That genus includes several hundred individual species of molds, many of which cause crop damage. One of these molds, for example, is the pathogen that caused the Irish potato famine of the 1840s.
The bottom line: root rot is not ruining Christmas in Oregon. In fact, Northwest Christmas tree growers say they expect to have a good year this year, due to an improved price for Noble fir trees after years of low prices due to oversupply.
According to the Pacific Northwest Christmas Tree Association, growers will harvest about 6.5 million trees in Oregon and 2.3 million trees in Washington this year. Christmas trees from the Northwest are sold in big box stores across the country and exported to Mexico, Asia, and South America.