Introduction and Spread of Nonnative Species

• In timber, produce, seeds, or nursery stock.

• In wood used for packing crates. The Asian gypsy moth and the Formosan termite were introduced in this manner.

• In freight viaby railway cars, tractors, aircraft, automobiles, bicycles, ships, and other vehicles.

• In ballast water dumped from ships.

• On hiking boots, camping equipment, and lawn furniture.

• In or on soil.

Negative Impacts of Invasive Species

• Invasive species control describes basic strategies available for solving exotic species problems.

Four basic strategies are available for solving exotic species problems: prevention, eradication, suppression, and biological control.

1. Prevention is the identification and interdiction of exotic species or their propagules before they enter the United States.
2. Eradication is the complete elimination of a population of an introduced exotic. It is effective against relatively small, localized infestations but requires intense effort and may be relatively expensive. In the case of plants, extensive use of herbicides is usually necessary, and some injury to desirable plants or the surrounding environment may be unavoidable. Eradication of large, well-established populations usually is not feasible.
3. Suppression is the periodic control or elimination of a population of exotics within a generally infested area. Suppression offers only a temporary solution to the exotic problem, and generally must be repeated at regular intervals. It generally becomes a permanent maintenance project unless biological control can be established.
4. Biological control involves the identification and introduction of an exotic species' natural control agents, usually herbivores, predators, parasites, or pathogens from its native environment. This is an expensive and time-consuming process because extensive research must be conducted to ensure that the proposed control agent will not cause further problems in its new environment. Biological control, if successful, brings the exotic species into balance with its environment so that it continues to be a component of the plant community but will not dominate it. However, biological control is not always possible or practical. (SAMAB 1996e).

Control of invasive species in the the Southern Appalachians

Control of exotic species on public land iscomplicated by the patchwork of jurisdictions; national parks, national forests, state, and private lands vary considerably in their approach to exotic species control. Of federal lands in the Southern Appalachians, only national parks have programs to control exotic plants. Approximately 40 invasive plant species are currently controlled in national parks in the region. Land managers cite the lack of money and personnel as the most serious immediate impediments to control. Althoughland managersare aware of the problem, addressing it will be difficult without additional resources (SAMAB 2001).

National forests in the Southern Appalachians have generally not attempted to control exotic plants except for kudzu, which has serious localized impacts on forestry. In fact, nonnative plants such as crown vetch, lespedezas, white dutch clover, and tall fescue have commonly been planted for erosion control after timber harvests and road construction, or as food for wildlife. Other exotics, such as privet, threaten to become problems in spots on national forests. Where national parks adjoin national forests and other federal and state ownerships, uncontrolled infestations of exotic plants often cross boundaries and create continuing management problems for the parks (SAMAB 2001).

In recent years, the Federal Government has increased support for the control of invasive species. On February 3,1999, President Clinton signed an Executive Order (#13112) to strengthen the control of invasive species by preventing introductions, minimizing damaging effects of invasive species, monitoring invasive species populations, conducting research, and restoring ecosystems and habitats (USDA Forest Service 2000).

Exotic plant species have been introduced into the Southern Appalachians since the beginning of European settlement of the region. Many of these introductions have posed no problems, remaining essentially within the boundaries of human cultivation. Some, however, have escaped and spread, displacing native vegetation, causing ecological disturbance and, in some cases, causing economic loss or impairing land use (SAMAB 1996e).

Most Invasive Plant Species in the Southern Appalachians

SAMAB formed the Southern Appalachian Native Plant and Invasive Species Initiative to increase understanding and awareness of invasive plants in the Southern Appalachians. As a part of this initiative, an Invasive Plants Assessment is being conducted to determine the extent and impact of invasive plants in the Southern Appalachians. One of the initial results of this assessment is to identify the most problematic invasive plants on public land of the region. SAMAB queried 41 state, Federal, and nongovernmental agencies about nonnative species. Although a total of 263 plant species were reported as invasive within the region, with most agencies reporting a particular set of "dirty dozen" species which posed their greatest ongoing and potential management headaches (Table:Frequently reported invasive plant species on public land in the Southern Appalachians). Some of the most frequently reported invasive plants are described below (National Park Service 1999). Links direct readers to species descriptions in "Exotic Pest Plants of Southeastern Forests" (Miller 2001).

A more extensive list of nonnative invasive plantsin the Eastern United States can be found at a website maintained by The University of Georgia, the USDA APHIS PPQ and the USDA Forest Service Forest Health Technology Enterprise Team. This sitecontains a synthesis of recent publications by the USDA Forest Service, National Park Service, U.S. Fish and Wildlife Service, USDA APHIS PPQ, and the Southeast Exotic Pest Plant Council. It covers identification characteristics, distribution, and control options for 97 tree, shrub, vine, grass, fern, forb, and aquatic plant species that are invading the Eastern United States. For each species, a menu of control options is presented, including mechanical treatments, specific herbicide prescriptions, and, for selected species, recent advances in biological control.

Japanese honeysuckle, Lonicera japonica, was introduced to the United States for erosion control before 1860. Most honeysuckle occurs in the Piedmont, where it is found in greatest abundance is in abandoned cropland, or rolling uplands with loamy, well-drained soils (Craver 1982). Large "impenetrable" mats occur in some areas (Stransky 1984). It competes with young timber in 10 percent of forest land from Georgia to Maryland. In South Carolina forests, the average volume occupied by honeysuckle was 12,813 ft³/ac (897 m³/ha) with a range of 1422-26176 ft³/ac (100-1932 m³/ha) (Giles 2001).

From a practical viewpoint, Japanese honeysuckle cannot be eradicated. However, it can be controlled by shading. Percent of tree stocking has an effect on density, but not occurrence, of honeysuckle. In a study conducted near Nacogdoches, Texas, Japanese honeysuckle grown in an open field was nearly 8 times more prolific than honeysuckle grown beneath a forest of shortleaf (Pinus echinata) and loblolly pine (P. taeda) (Hall and Alcaniz 1968). Stem length per plant for open-field honeysuckle was 8,369 cm and 1,009 cm beneath trees. Therefore, clearcutting should be used with caution in some areas and, instead, group and single-tree selection cuts might be used to assure control by shading. Both mechanical and chemical means have been used to control honeysuckle. Velpar herbicide appears to be more effective than mechanical suppression. Among successful mechanical methods during site regeneration arebrush-hogging and planting seedlings or disking with natural regeneration (McLemore 1984, Giles 2001).

Although Japanese honeysuckle is considered to be a forest pest, it does offer some benefits. It is eaten by at least 14 wildlife species and is favored in some areas by deer. In a study of seasonal nutrient quality and digestibility of Japanese honeysuckle, it was found that seasonal variations in nutrient quality and metabolic usefulness of leaves and twigs are closely associated with plant growth and tissue maturation. During rapid spring growth, leaves and twigs are most succulent and their dry matter fractionare highest in nutrition and digestibility. During the summer, as twig growth slows, fiber deposition increases in maturing tissues and quality and digestibility decline. Twigs express this decline to a greater degree than leaves. Throughout the year, leaves generallyhave highnutrientcontent and are more digestibile than twigs (Giles 2001).

Japanese honeysuckle is also valued for erosion control and its aesthetic qualities.