The following nonnative insect and pathogen species are threats to forest health in the southern Appalachians:

Insects	Pathogens
Gypsy Moth	Chestnut Blight
Asiatic Oak Weevil	Dutch Elm Disease
BROKEN-LINK Hemlock Wooly Adelgid	Butternut Canker
Balsam Wooly Adelgid	BROKEN-LINK Dogwood Anthracnose
Asian Longhorned Beetle	Sudden Oak Death
Emerald Ash Borer

Asian longhorned beetle oviposition site

The Asian longhorned beetle, Anoplophora glabripennis, is a recently introduced pest from China. It is believed to have entered the United States inside solid wood packing material from China (USDA Forest Service 2002). It was first discovered in the United States in 1996 in New York. In 1998, an infestation was found in Chicago. In 2002, Asian longhorned beetles were found in New Jersey. Eradication programs have been initiated and it is yet undetermined whether this pest exists elsewhere in the United States.

Asian longhorned beetle adult

Adult Asian longhorned beetles are 1 to 1 1/2 inches in length with antennae that can be 1 to 2 1/2 times their body length (USDA Forest Service 2002). Adult bodies are black with white mottles. The antennae have a distinctive black and white banding pattern. The feet often have a bluish tinge. After mating, females chew dime-sized depressions in the bark of hardwoods to lay their eggs in (USDA APHIS 2004). After hatching, the larvae bore into the tree to feed upon the vascular tissue. The larvae continue to bore into the wood of the tree, forming large tunnels and galleries. The larvae pupate in the wood near the surface. The newly formed adults emerge through large, perfectly round exit holes (3/8 inch in diameter). Emergence usually occurs from June to October (USDA Forest Service 2002).

Asian longhorned beetle larvae

The damage resulting from an Asian longhorned beetle infestation reduces the commericial value of trees and can kill trees if the infestation is severe (USDA APHIS 2004). Many species of hardwoods can serve as hosts (USDA APHIS 2004), including:

• Maples (Acer)
• Horse chestnuts, buckeyes (Aesculus)
• Willows (Salix)
• Elms (Ulmus)
• Birch (Betula)

The major host species for Asian longhorned beetle are usually not a dominant overstory species in southern Appalachian forests. However, they can comprise a significant proportion of the overstory, increase biodiversity, and are important ecologically. If Asian longhorned beetles further expand their range and become established in large forests, the potential exists for it to spread into the southern Appalachians. Infestations could reduce biodiversity and alter species compositions of southern Appalachian forests. The extent and severity of the damage is unknown.

Asian longhorned beetle damage

Emerald ash borer current distribution

Emerald ash borer, Agrilus planipennis, is a newly introduced species (found in 2002) from Asia. Populations have been found in southern Michigan, Ohio, and Indiana (USDA Forest Service 2004). Maryland and Virginia have also reported infested tree nurseries. Larvae feed on phloem and sapwood of ash species (Fraxinus spp.) girdling and killing the trees. In America, white ash (F. americana), green ash (F. pennsylvanica), and black ash (F. nigra) have been infested as well as ornamental varieties of ash.

Emerald ash borer adult

The emerald ash borer usually has a one year life cycle. Adults emerge in early summer. The adult beetles usually live for about three weeks, during which they are very active during warm, sunny days (USDA Forest Service 2002). Adults feed upon ash leaves and lay their eggs in bark crevices of ash trees. Once the eggs hatch, larvae bore into the cambium layer and begin making winding S-shaped galleries. The larvae overwinter inside the tree and pupation begins in late spring. The new adults emerge in early summer, leaving a clear cut, D-shaped exit hole (USDA Forest Service 2002).

Emerald ash borer larva

Adults are large, slender beetles (7-14 mm in length) (USDA Forest Service 2002). Adult bodies are green to bronze in color. The wing covers are noticably metallic green in color. The larvae are 26-32 mm in length, cream colored, and dorsa-ventrally flattened.

Typical infestation symptoms include the presence of D-shaped exit holes, vertical splitting of the bark, and epicormal sprouts (USDA Forest Service 2002). Crown dieback usually occurs after two years of infestation. Trees often die after 3-4 years of infestation.

Although ash species do not dominate the southern Appalachians as they do in other eastern forests, they still comprise a significant proportion of the forest canopy. Emerald ash borers have the potential to severely reduce the occurence of ash throughout the southern Appalachians, alter the ecosystem and reduce the forest canopy biodiversity. For more information on emerald ash borer click here.

Emerald ash borer exit hole

Emerald ash borer infestation
symptoms, epicormal growth

History

Sudden oak death zone line symptoms

Sudden oak death, caused by the pathogen Phytophthora ramorum, is a potentially devastating disease. Recently, P. ramorum has been found in nurseries in the eastern United States. P. ramorum, the causal agent of sudden oak death, has not been found outside of imported ornamental shrubs in the eastern United States. The disease, first found in coastal California in 1995, was thought to be restricted to California but in April 2004, P. ramorum was detected in nurseries in Georgia. Surveys in other states followed, leading to infected nursery stock being found in 7 other states. The disease has not been found outside of imported nursery stock, but some plants were sold to landowners before it was discovered that they may have been infected. Once sudden oak death was found in infested nursery stock, quarantines were initiated on some California nurseries and growers until they were declared to be free of P. ramorum.

Symptoms and Impacts

Sudden oak death bleeding canker symptom

Since sudden oak death was discovered in 1995, tens of thousands of tanoaks (Lithocarpus densiflorus), coast live oaks (Quercus agrifolia), and California black oaks (Quercus kelloggii) have been killed by a newly identified fungus. The impacts on eastern oaks, one of the most abundant groups in the southern Appalachians, and closely related species are unknown but sudden oak death has the potential to devastate populations and severely alter the ecoystem functions and biodiversity of eastern hardwood forests. Huge economic impacts to the hardwood timber industry could also incur.

Sudden oak death causes cankers on stems of oaks. Trees often bleed a reddish or black ooze from the cankers. Under the bark of infected trees, necrotic tissue surrounded by black zone lines often can be found (USDA Forest Service 2002). Cankered trees may survive for one to several seasons. Once crown dieback begins, leaves turn brown within a few weeks.

The disease usually does not spread from oak to oak since it rarely produces spores from infected oaks. However, the pathogen infects many species of shrubs. Two common genera for host plants are Rhododendron (common in the Appalachians) and Camellia (USDA APHIS 2004). These shrubs are not killed, but spores are readily produced on infected leaves, which display spotting and blighting symptoms. Another common symptom is twig dieback.

Survey and Detection

P. ramorum symptoms on Rhododendron

Many pathogens exists that can exhibit similar symptoms as P. ramorum thus correct diagnosis requires complicated labratory analyses. For this reason, surveying and detection of sudden oak death quickly becomes an expensive endeavor. The potential impacts of sudden oak death is so great that, despite the cost, large scale survey projects are underway. USDA-APHIS PPQ (Plant Protection and Quarantine), as well as state agricultural agencies are conducting nursery surveys, and sending samples of symptomatic plants for lab analysis. A large scale effort to track down any plants that were sold to homeowners for inspection is also underway. Forest transects near high risk areas are also being surveyed by state forest agencies and the USDA Forest Service. The Great Smoky Mountains National Park has also initiated a survey program. Any infected material is destroyed along with nearby individuals that could serve as a host.

For more information as well as an updated host list click here.