Dec. 23, 2003 — Christmas trees are bringing home more than holiday cheer in California: some are also bringing disease.
A fungal tree disease called pitch canker has popped up on Christmas tree lots, in landscaping and in native forests of 19 California counties. Christmas trees could spread the disease further.
"This is affecting lots of pines," said plant pathologist Tom Gordon of the University of California at Davis. The disease is not deadly to trees, but can kill limbs and create unsightly and hazardous conditions.
The Christmas tree that is the most worrisome is the fast-growing Monterey Pine, native to California's Central Coast mountains, and a favorite of the "cut-your-own" Christmas tree farms, Gordon said. It's also an important lumber tree in countries around the world and has been considered for listing as a threatened species in its native range.
Christmas tree lots already found with infected Monterey pine trees include those in San Mateo County, north of San Francisco, and the populous southern coastal counties of Los Angeles, Orange and San Diego. So far pitch canker has not made it inland to the Sierra Nevada, said Gordon, and officials would like to keep it that way.
The pitch canker fungus, Fusarium circinatum, gets from tree to tree by hitching a ride on insects, Gordon explained. The fungus usually kills just the limb or area on the trunk where it first infects. Dead limbs then pose the hazard of falling on roads or houses. To help keep the disease from spreading to landscaping trees or forests, Californians are being asked to recycle, chip or compost their trees as soon as they are finished serving as holiday decorations. They are also being asked not to transport trees east past Interstate 5, which roughly divides the coastal ranges from the uninfected Sierra Nevada.
"A good general rule is to keep the trees in the area where they were grown," said Gordon. Even a healthy looking Christmas tree might harbor the disease, he said.
Pitch canker was originally discovered in pine plantations in the Southeastern United States in the 1940s. It was discovered in California in 1986.
"We donâ??t really know where it came from in California," said U.S. Forest Service's Susan Frankel. "It could have come in on firewood, needles, root stock, Christmas trees. Who knows?"
The point now, she said, is to keep it from spreading.
Among the trees vulnerable to pitch canker are gray pine, coulter pine, Torrey pine, ponderosa pine, shore pine and Douglas fir.
