Archive for the ‘Invasive species’ Category

Help the Hemlocks

Tuesday, March 10th, 2009

I first saw the hemlock wooly adelgid in action about 15 years ago. Its telltale wooly white egg masses appeared on a few branches of three hemlock trees in my next-door neighbor’s yard in Park Slope, Brooklyn. Within three years the trees were dead. Since then the insect, which arrived in North America from Asia in the 1920s, has become a major scourge of eastern forests from Maine to Georgia. It is spreading rapidly into the oldest and largest hemlock stands in the Southern Appalachians, where some of the trees are 800 years old and more than 175 feet tall.

In fact, new research suggests the hemlock woolly adelgid is killing hemlock trees even faster than expected in the Southern Appalachians and most of the region’s hemlocks could be dead within the next decade. The hemlock plays a fundamental role in the ecology and hydrology of mountain habitats. Its thick, evergreen canopies help cool mountain streams that are home to trout. Many birds find shelter and places to nest in the hemlock’s evergreen boughs. In one study, 96 percent of all wood thrush nests found by surveyors were in hemlocks. Some warblers only nest in hemlocks.

Few of the growing number of U.S. native trees beset by pestilence have a federal task force devoted to their survival. The hemlock does. Among other things, the Hemlock Wooly Adelgid Action Team coordinates control efforts and runs a public education and outreach campaign. While homeowners can treat individual trees with horticultural oils or chemical pesticides, this isn’t practical for entire forests of afflicted trees. The most promising backwoods treatments found so far are two tiny nonnative beetles that dine voraciously on adelgids (and, scientists say, only adelgids). Tests in Connecticut and Virginia show that these beetles can reduce hemlock wooly adelgid populations by 47 to 87 percent in five months. The beetles have been released in selected areas throughout the Southern Appalachians.

Still, the scale of the hemlock wooly adelgid epidemic is so huge that scientists and public land managers won’t be able to contain it without the public’s help. Details on how you can monitor and treat trees on your own property and get involved in efforts to protect hemlocks in the wild are on the Hemlock Wooly Adelgid Action Team’s website.

Will Somebody Please Adopt This Tree?

Friday, December 12th, 2008

This year there seem to be more Fraser firs than ever for sale in my neighborhood, the Upper West Side of Manhattan. No big surprise. Woody plant expert Michael Dirr once called them the “Cadillac of Christmas Trees.” Fraser firs have a gorgeous pyramid shape and a profusion of soft, short needles arranged spirally around the branches. They also smell great. 

What is shocking is the stark contrast between the countless Fraser firs that line city streets, lending a festive air during the holidays, and the gray skeletons found in the tree’s native habitat. The species is endemic to the seven highest peaks in North Carolina, Tennessee, and Virginia; it is found nowhere else in the world. But in the past fifty years the number of mature Fraser firs on these mountains has declined by as much as 91 percent. The species is threatened with extinction in the wild largely because of an introduced insect, the balsam wooly adelgid, which first appeared in the southern Appalachians in 1957. The insect attacks by entering the trunk of a tree through fissures in its bark that develop as it ages; two to seven years later, the tree is dead.

Another threat to the Fraser fir: As temperatures rise due to global warming, it has nowhere to go. It can’t migrate upward to cooler, higher habitat because it already grows at high elevations on those seven mountains, in forests believed to be ice age relicts. When the last of the Pleistocene glaciers retreated north, Fraser fir was left stranded on these mountaintops, which have climates similar to those of Maine and Quebec. 

Someday it may be possible to see Fraser fir only on Christmas tree farms, or frigid Gotham streets.

The species is in the National Collection of Endangered Plants, under the auspices of the Center for Plant Conservation, a coalition of botanical gardens. But Fraser fir deserves to live wild and free, outside the cultivated confines of a farm, a garden collection, or a seed bank. For a number of years, the National Park Service reportedly tried to control the balsam wooly adelgid at Clingman’s Dome in Tennessee, using the only effective control known to date — coating each limb of each tree with a mild soap. But this proved too time consuming and costly and was given up.

Scientists and government officials have their hands full with invasive pests and imperiled plants, not to mention budget cuts and a host of other impediments. But citizens can fill the gap. Another endangered native conifer, the Florida torreya, has a group of activists, the Torreya Guardians, advocating and acting on its behalf. Friends of the Fraser fir anyone?

Invasive Truffle

Thursday, May 29th, 2008

A paper in the journal New Phytologist has truffle aficionados in a panic. Written by Claude Murat from the Dipartimento di Biologia Vegetale dell’Università di Torino and his colleagues, it documents the recent discovery of the aggressive Chinese black truffle, Tuber indicum, at an Italian truffle plantation. “We dread that T. indicum will spread all over Europe and crowd out T. melanosporum and perhaps other truffle species,” Murat told Science News. Lovers of the fungal lumps, underground reproductive structures that fetch astronomical prices in gourmet markets, turn up their noses at the Chinese species, considered much less flavorful and aromatic than European natives like the Périgord black truffle, T. melanosporum, and the even more precious Piedmont white truffle, T. magnatum. The record price of a single white truffle, $330,000, was set in December 2007, for a 3.3-pound specimen unearthed near Pisa by Luciano Savini and his dog Rocco.