Emerald Ash Borer |
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Background
Overview
In June, 2002, the emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) was identified as the causal agent in ash tree decline and mortality in the Detroit metropolitan area. For several years before this identification, homeowners and arborists in southeast Michigan attributed the loss of their ash trees to “ash yellows”. The trees exhibited a top-down crown dieback, dense sprouting from trunks (epicormic shoots), and other signs of tree stress typical of ash yellows. The infested ash trees displayed dying crowns in the second year of infestation and most died from EAB within five years.
This non-native beetle was unknown in North America until its discovery in southeast Michigan and neighboring Windsor, Ontario, Canada in June, 2002. Before the end of the month, the Michigan Department of Agriculture (MDA) issued a quarantine of six southeastern counties (Livingston, Macomb, Monroe, Oakland, Washtenaw, and Wayne) to prevent and control the spread of EAB. Under the quarantine, ash trees, branches, logs, and firewood could not be moved from the infested counties.
Throughout 2002 MDA conducted extensive surveys in the quarantined counties to determine the extent of the infestation. Additional EAB detections spurred agriculture officials in Ohio and Indiana to deploy survey teams of their own. Subsequently, EAB was detected in Ohio in February 2003 and in Indiana in April 2004.
APHIS worked with State cooperators to develop strategies to detect, control and ultimately eradicate EAB. Detection efforts consisted of using sentinel trees (trap trees) for survey, federal and state quarantines were issued to control the spread of EAB, and eradication efforts focused on the removal all host trees within a half mile radius of an infested tree.
While EAB program partners collectively worked to contain the infestation, the scientific community aggressively studied EAB to learn more about its biology. Early on, researchers agreed that controlling the artificial spread (human-assisted) of EAB was critical for the program. Also, the evaluation of patterns of ash decline and mortality, together with the examination of individual ash trees, provided researchers with a solid foundation to date the EAB’s arrival in North America—in the early to mid 1990s.
Today, EAB infestations have been detected in 10 states; Illinois, Indiana, Michigan, Ohio, and Pennsylvania, together with isolated infestations in Maryland, Missouri, Virginia, West Virginia, and Wisconsin. Strategies to manage the pest currently focus on survey activities using a new detection tool, a panel trap, along with regulatory activities and public awareness campaigns to prevent human-assisted movement. Outreach efforts have emphasized “Don’t Move Firewood”, as firewood movement is a primary method of artificial spread for this pest. APHIS continues to identify effective tools to manage and control EAB populations.
This non-native pest poses an enormous threat to our urban and rural forests. EAB kills stressed and healthy trees and is so aggressive that ash trees may die within two or three years after they become infested. If it is not contained and managed, the impact of emerald ash borer beetle in North America will be similar to that of the devastation caused by two fungal diseases, Chestnut blight and Dutch elm disease, which destroyed dominant species of woodland and urban forests in the 20th century.
Non-native organisms, like the emerald ash borer, are often more destructive in a new range because they do not have natural population controls such as parasites, predators, or diseases. Host plants, innocent of previous contact with an organism, have not had time to adapt and develop effective defenses against them.
Impacts of the Emerald Ash Borer
Emerald ash borer is a serious pest and quarantines are established around infestations. Larvae feed in the phloem and outer sapwood producing galleries that eventually girdle and kill the tree. This invasive pest has had a devastating impact on communities that now face significant tree removal costs associated with dead or dying ash trees that pose a threat to public safety.
Ash trees are as important ecologically in the forests of the northeastern United States and eastern Canada, as they are economically. Ash trees fill gaps in the forest and provide shade for the forest floor. They are very desirable for urban tree planting because they grow well under difficult conditions. Ash wood is valued for flooring, furniture, sports equipment (e.g., baseball bats, hockey sticks, oars), tool handles, and supplies for dairies, poultry operations and beekeepers.
Other repercussions include decreased property values, losses in the long-term supply of ash wood, decreased air quality, increased electricity use during hot weather, and negative impacts on Native American cultures that use ash wood for traditional crafts and ceremonies. In addition, there are other detrimental impacts on wildlife and natural ecosystems. As a vital component of forest succession, ash colonizes and stabilizes disturbed areas. In addition, ash is one of the few native trees able to out-compete weeds that prevent most other species from becoming established.
States which become infested could lose billions of dollars in forest products and quarantines imposed by state and federal agencies may have serious consequences for plant and wood products industries. Severe damage may also occur within the tourist industry with the loss of tree cover in campgrounds.
Biology
Mating occurs shortly after emergence, with females mating multiple times. The female may lay 1-23 eggs at a time, with one being the norm. Each female can lay 60-90 eggs in their lifetime, depositing them individually in bark crevices on the trunk and major branches. Eggs typically hatch in 7-10 days. Minute larvae bore through the bark and into the cambium where they feed on the phloem. As they feed, the larvae create long serpentine galleries (20-30 cm.) filled with frass, which enlarge in width as they grow. Larvae continue development until late summer or early fall. Pupal development is variable according to humidity and temperature. After pupae transform into adults in the spring, the beetle takes 1 to 2 weeks before it emerges through D-shaped exit holes 3-4 mm wide. Adults prefer clear, calm days and the warm, sunny sides of the trees and can be observed in the sunlit portions of the crown. Adult females live approximately 22 days; whereas males live an average of 13 days.
Images
Hosts
In the United States and Canada only ash trees (Fraxinus spp.) are known to be affected. Ash trees are widespread in the United States and all 16 native ash species are susceptible to EAB attack. Six native ashes are valuable commercial species, while the others are important in communities as integral parts of rural and urban landscapes. The national urban impact from EAB could exceed $20 billion. Healthy ash trees of any size (from as little as two inches in diameter) can be affected.
Distribution
The emerald ash borer’s native range includes China, Mongolia, North Korea, South Korea, Japan, Taiwan, and the Russian Far East.
In North America, EAB infestations are known to exist in Illinois, Indiana, Maryland, Michigan, Missouri, Ohio, Pennsylvania, Virginia, Wisconsin and West Virginia, as well as the Canadian provinces of Ontario and Quebec
Symptoms
- Symptoms of emerald ash borer include:
- Initial thinning of the foliage or crown dieback.
- Epicormic shoots may or may not be present on declining trees.
- Woodpecker injury--woodpeckers strip away small patches of bark, so that they can extract the borers.
- D-shaped emergence holes, about 3 mm in diameter.
- Larval galleries--typical galleries meander, bending suddenly, and are packed with frass.