Tree-Killing Mistletoe Threatens Local Forests : Environment: Federal crews are working to eradicate cousin of popular Yuletide symbol, which is strangling pines in Los Padres and big arbores in Angeles.


At a time when mistletoe sprigs tied with red ribbon are beginning to appear in grocery stores and Christmas shops, the U.S. Forest Service is trying to control mistletoe in the forest, where the popular Yuletide symbol is a tree-killing parasite.

True mistletoe, with its broad, furry leaves, is of less concern than a more virulent cousin that is strangling Jeffrey pines on top of Pine Mountain in the Los Padres National Forest and big trees in the Crystal Lake recreation area in the Angeles National Forest.

The more threatening variety, known as dwarf mistletoe, is so pervasive that foresters say they must take swift action to avoid losing a 200-acre stand of trees at Pine Mountain north of Ojai.

“If we let it go any longer, all the trees up there will die and it will be Bald Mountain instead of Pine Mountain,” said Terry Austin, resources forester with the Los Padres National Forest.


Los Padres officials are developing a plan to eradicate the dwarf mistletoe and are asking for comments from interested parties.

Control measures will probably include pruning affected branches and, in some cases, removing infected trees. No chemical treatment is planned.

The felled trees would be replaced with native species that are not susceptible to mistletoe infestation, Austin said.

The plan is to attack the parasite in three 20-acre stands near Pine Mountain Campground.


“That’s our most popular campground because it’s a real forest,” Austin said of the site, which is covered with 100-foot-tall pines and affords ocean views. “People can enjoy the view up there and still be in the trees and enjoy the smells of the forest.”

Austin is in the process of tagging all of the trees, ranking them by degree of infection and the type of treatment they will need. She said people, possibly misguided campers fearing all marked trees would be cut down, have been removing the tags and making her job more difficult.

“I have tagged 580 trees so far and 75 of them were taken down,” she said.

Angeles forest officials are in the fourth year of a five-year attack on mistletoe near the Crystal Lake campground and picnic area north of Azusa, where ponderosa, Jeffrey pines and white firs have been “severely impacted by mistletoe,” said Karen Fortus, resource officer for the Mt. Baldy District of the forest.

About 800 trees have been marked for treatment, and each spring, crews have cut infested limbs and branches, which are chipped into compost and spread on the forest floor. However, several trees as tall as 150 feet have had to be removed, Fortus said.

Both true mistletoe, which mainly attacks hardwoods such as oak, and the dwarf variety that most often infests pines and other conifers, are naturally occurring parasites that can ravage trees weakened by drought or disease.

Both types are parasitic, but dwarf mistletoe is more harmful because it depends entirely on the host tree for nourishment, causing branches to swell and break as it slowly saps the tree of life.

Dwarf mistletoe spreads quickly as the female of the species produces berries. As the berries swell with water in the spring, the pressure causes them to burst, spitting out sticky seeds that can travel 30 or 40 feet.


“Just imagine if the wind is blowing how far those seeds could travel,” Austin said. “With their sticky coating, those seeds stick wherever they land. And once a tree is heavily infected at its crown, it usually dies within 15 years.”

Mistletoe is pervasive, and control efforts often are focused on popular recreation areas in tall timber, both to preserve the big trees for the enjoyment of visitors and because trees killed or weakened by mistletoe become a safety hazard.

Steve Bear, resource officer for the Tujunga district of the Angeles forest, said foresters there have had to do “selective surgery” from time to time, including a couple of years ago, when about 50 trees were removed from a heavily infested area at Mt. Gleason.

Mistletoe is also common in the Saugus district of the Angeles forest north of the Santa Clarita Valley, but it does not now pose a serious problem, district ranger Mike Wickman said.

Rick Burgess, a board member of the Channel Islands branch of the California Native Plant Society, said he supports the Forest Service’s efforts to suppress the pesky plant.

“As long as they are very selective and they don’t remove too many trees, that might be an effective way of controlling the mistletoe,” he said.

Austin of the Los Padres forest said that the drought years of the late 1980s and early 1990s allowed a true or Christmas mistletoe to become firmly embedded in the cottonwoods and willows around Lion Campground in Rose Valley.

There were a lot of broken limbs and weakened trees in the area. She has since tagged all of those trees as well and has tracked their recovery.


“We did some pruning and some tree removal there and, with the rains, they seem to be coming back,” Austin said. “But it’s much more urgent at Pine Mountain because if they go untreated, they will die.”

The natural course of lightning-caused fires in the forest would probably eventually take care of the problem, Austin said. “But we don’t allow campgrounds to burn,” she said.

“People may be alarmed that we’re going to be cutting down trees up there,” Austin said. “But once they understand that we are trying to save the trees for the future, we hope they will understand.”