Green Hitch-hikers: Invasive Species Hitching a Ride into the Park
Ken Voorhis, Great Smoky Mountains Institute
The Smokies added two new species to its list of known park species this spring, but they were species that should not be here. One is a shiny green beetle, which could cause the death of hundreds of ash trees in and around the park. The other is a bright green tree frog and the jury is still out as to whether it will harm the park. Both probably hitched a ride to the park on visitors' vehicles and/or in firewood brought into the park.
The green tree frog (Hyla cinerea) appears to have been breeding in one spot in Cades Cove near the campground for several years. Photographer Brian Shults first called it to the attention of park officials in 2011 but we were not able to relocate the population until this June. This species is native to the coastal plain of southern states, a long way from the Great Smoky Mountains. While they certainly are feeding on insects here in the park, they may or may not have any impact on any of them, or on the other species of amphibians that share their breeding ponds. The park plans to study the tree frogs in the park to determine if they pose a threat. In the meantime, check over your vehicles and trailers, especially in wheel wells and underneath, for any unwanted hitch-hikers before visiting the park.
The emerald ash borer (EAB) was found near the Sugarlands Visitor Center and in the Greenbrier area in late May, 2012. Since it was first found in Michigan in 2002, EAB has spread to 15 states and two Canadian provinces and killed tens of millions of trees. Movement of firewood and unprocessed logs are the primary means of their spread, and it is not the only pest to move this way. As of March, 2012 emerald ash borer and thousand cankers disease of walnut have each been detected in six counties in east Tennessee. Another species moved by firewood, the Asian long-horned beetle, has been found within 300 miles of the park to the north.
Although these pests eventually will have an impact on the forests of the Smokies the best way to slow their advance is by not moving firewood and untreated logs. If you are traveling to the park to camp and want a campfire, use either dead and fallen trees near your campsite or buy firewood that is USDA APHIS certified pest free. APHIS does not provide a list of certified firewood suppliers so you may have to search online for sources near your destination. Certified pest free firewood will have a certification stamp for a particular pest right on the package.
In advance of their arrival, the park has conducted an inventory of its ash trees using volunteer citizen scientists from our neighboring communities. The Smokies has two ash species found in several forest communities: white ash is common across a wide range of elevations and green ash is less common and at low elevation. While ash is not found in pure stands, the ash borer is likely to find these scattered trees and kill many of them. Park resource managers have begun surveying ash trees for symptoms of ash borer infestation, as well as working with Dr. Richard Baird of Mississippi State University to survey walnuts for symptoms of thousand cankers disease.
Thousand cankers disease (TCD) is a caused by the fungus Geosmithia mobida that causes decline and mortality in black walnut and which gains access to the tree with the help of the tiny (2 mm long) walnut twig beetle. Butternut is an uncommon relative of black walnut in the Smokies and is also believed susceptible to TCD. Symptoms of TCD can take ten years to develop and include yellowed and dying leaves and branch dieback. Infested branches will have pencil point size emergence holes and careful peeling of the bark will reveal tiny larval development tunnels (galleries) and dark stained canker infections.
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Did You Know?
Ninety seven historic structures, including grist mills, churches, schools, barns, and the homes of early settlers, preserve Southern Appalachian mountain heritage in the park. More...