“If we’d gotten imidacloprid in ’97, we could have saved a lot more hemlocks,” Gubler says.Īnd this effort is just a stopgap. They’ve had the most success with imidacloprid, a neurotoxin injected into the soil and absorbed by the hemlocks, which kills the adelgids for as long as seven years.īut for almost all of the trees, it was too late. Park officials started in 1997 with insecticidal soaps and oils, then pesticides, but were limited by the immense cost and logistical difficulties of reaching trees scattered throughout a mountainous forest to spray twice a year. Treatments were long on effort and short on results. “By 2002, we saw upwards of 95% mortality in all our hemlock stands,” Gubler laments. Within a few years, the trees started dying, first at warmer low elevations, then spreading rapidly throughout the park, exacerbated by gypsy moth infestation and drought. It was first spotted in Shenandoah in 1988, the year Gubler started working here. HWA first arrived in the Pacific Northwest from Japan in the 1920s and spread to Washington, D.C., and Richmond, Virginia, by the 1950s, likely through infected nursery plants.įrom there the adelgid has moved about 20 miles a year. Once a hemlock is infested, its death sentence is three to 10 years. With no natural predators in the United States, before long natural reproduction leads to thousands of the insects slowly starving the tree to death. Twice a year, the HWA lays between 50 and 300 eggs the young bite into the base of a hemlock needle and suck out sap, disrupting the flow of nutrients. The hemlock woolly adelgid ( Adeleges tsugae if you like Latin HWA for our purposes) is an aphid-like insect that takes its name from its sole prey and a protective white fluff it secretes to protect its eggs. The vicious attacker destroying this national natural treasure is no bigger than a speck of dust, which explains part of the difficulty in combating the threat. Hemlock wooly adelgids, the white clumps on this branch, are attacking eastern hemlocks. “Those are our heartbreak areas,” Gubler admits. Limberlost, saved by the Pollocks 100 years ago, had the oldest stand of old-growth hemlocks in the park, which now lie rotting on the ground. Instead of Five Forks and Appomattox, Gubler had the battles of Hemlock Springs, Rapidan Camp and Limberlost. For a decade, Gubler has been on desperate mission to try to save the trees, an effort that often seems more of a lost cause than the Army of Northern Virginia’s last desperate battles of 1865. Migrating songbirds such as the Blackburnian Warbler, Black-throated Green Warbler, Wood Thrush and Blue-headed Vireo seek out hemlocks almost exclusively.īut as the hemlocks have gone, so have the trout and songbirds. Hemlocks’ deep shade can cool stream water as much as 7 degrees Fahrenheit, ideal for brook trout. “Where you found hemlocks, you found particularly beautiful areas with unique ecosystems, shaded streams with brook trout and specific songbirds that needed that habitat,” says Rolf Gubler, Shenandoah’s biologist and forest pest manager. Workers building the President’s cabin were explicitly ordered to incorporate an old hemlock rather than chop it down. When President Herbert Hoover and his wife, Lou Henry, needed a place to escape Washington during the Great Depression, they picked a spot in a hemlock grove along the trout-filled headwaters of the Rapidan River. Some of these trees were up to 500 years old.Ī century ago, local legend holds, a particularly beautiful grove of old-growth trees was saved from loggers when George Freeman Pollock and his wife, Addie, owners of Skyland Resort, paid them $10 per tree to leave the hemlocks alone. Now 95% of them are dead, rotting on the forest floor or still standing above the canopy as gray ghosts, with a few scattered survivors living on borrowed time as their attackers literally suck the life out of them. Just 15 years ago, the eastern hemlock tree, the mighty Redwood of the East, was a scenic highlight of Virginia’s Skyline Drive, creating the shady groves that put Shenandoah National Park on the conservation map.
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