Emerald Ash Borer |
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Background
Overview
For several years, homeowners and landscapers in Southeast Michigan were concerned about the loss of their ash trees to “ash yellows,” thinking that the problem was due to a combination of disease, drought, pollution, acid rain, and poor soils. The trees exhibited a top-down dieback, yellowing leaves, dense sprouting from roots and trunks (“epicormic shoots”), and other signs of tree stress typical of ash decline or other native phloem borers such as two-lined chestnut borer. One-third to one-half of the affected ash trees’ branches died within a year, and most of the canopy was dead within two years.
The Emerald Ash Borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), was identified as the causative agent in ash tree mortality and decline in the Detroit metropolitan area. This beetle was unknown in North America until June 2002, when it was discovered killing ash trees in southeast Michigan and neighboring Windsor, Ontario, Canada, located across the river from Detroit, Michigan. Before the end of the month, the Michigan Department of Agriculture 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 affected counties.
The phase of decline in individual ash trees examined during survey activities suggests that EAB could have been established in Michigan and Canada almost a decade ago. APHIS worked with cooperators in the development of a cooperative strategy to contain and ultimately eradicate EAB. Control efforts consist of removing all host trees within a half mile radius of an infested tree, using sentinel detection or trap trees for survey, and conducting visual surveys to delimit the area of infestation.
While the survey continued in the Lower Peninsula of Michigan, indicating that their infestation was more wide spread than initially anticipated, early in 2003 EAB larvae also were detected on four residential properties in Lucas County, Ohio. Then in August, more beetles were positively identified from the city of Hicksville in Defiance County. Subsequent infestations have also been discovered in fourteen additional counties in Ohio.
Neighboring Indiana discovered their first EAB infestation in April 2004 in ash trees located in a Steuben County campground, approximately 40 miles north of Fort Wayne. With continued survey in this state, the infestation has been discovered in another six counties. Both Indiana and Ohio are conducting state-wide surveys in 2006 to determine the extent of their EAB infestations.
On June 9, 2006, APHIS confirmed the detection of Emerald Ash Borer in Illinois for the first time. A homeowner in a rural subdivision near Lily Lake, about 40 miles west of Chicago in central Kane County, discovered the beetle and alerted APHIS officials. APHIS and Illinois Department of Agriculture (IDOA) officials immediately began delimiting survey activities to determine the extent of the EAB infestation in Kane County. Detection surveys are being conducted in the nine counties surrounding Kane County, which include areas in Wisconsin. In addition, the program will conduct an inventory of nurseries, campgrounds, and other high-priority sites, such as new residential or recent commercial developments with ash tree landscaping.
A second infestation was detected on July 12, 2006, in the Cook County village of Wilmette by Wilmette Village Foresters. A survey has begun to determine the extent of this infestation. On July 21, 2006, EAB was also detected in the northwest portion of Evanston in Cook County. These detections were made as a result of an EAB state survey that had been intensified as a consequence of other EAB detections in the state.
In late August 2003, Emerald Ash Borer was found in Maryland at a Prince George’s County nursery. An investigation uncovered a Michigan nursery owner had shipped 123 ash trees to southern Maryland, a violation of the Michigan quarantine. A portion of the ash trees in Maryland were sold and sent to Virginia for planting in that state. These trees were traced down and then removed in the hopes of preventing infestations from developing.
The owner pleaded no contest and in December a District Court judge ordered him to pay the maximum $12,300 fine and spend 200 community service hours helping Michigan communities remove dead ash trees.
Maryland and Virginia continued to trap with sentinel trees and had no detections until September 2006 when Maryland discovered EAB in the Brandywine area. On August 22, 2006, two larvae were recovered from ash trees located in the Clinton/Brandywine area of southern Prince George’s County during ongoing survey and eradication activities begun after the detection of the insect in Maryland in 2003. Virginia examined their detection trees for the 2006 season, but found no EAB.
Over the next several months, USDA-APHIS and Maryland officials thoroughly investigated the area for the presence of the pest using several survey methods, including destructive sampling. In addition to survey, regulatory, and control activities, the program is planning an aggressive outreach and education campaign to enlist the support and cooperation of homeowners and businesses.
On June 26, 2007, APHIS confirmed the detection of emerald ash borer (EAB), in the Cranberry Township of Butler County, Pennsylvania, which is located 10 miles north of Pittsburgh. This detection was made by APHIS personnel conducting visual inspections for ash decline along Pennsylvania’s I-76 corridor in proximity to the Ohio border following the June 20, 2007, confirmed detection of EAB at an I-76 rest-area 5 miles into the Ohio side of the border. APHIS officials observed and investigated ash tree decline in the parking lot of a commercial establishment and captured two suspect specimens, which were confirmed to be EAB.
In response to this latest detection, surveys are being conducted by the Pennsylvania Department of Agriculture, United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine; Pennsylvania Department of Conservation and Natural Resources, Bureau of Forestry, Division of Forest Pest Management; Pennsylvania State University, Cooperative Extension, Department of Entomology; and certified arborists to further delineate the extent of the infestation. As a result, on Friday, June 29, 2007, EAB was confirmed in Allegheny County, Marshall Township. APHIS cooperated with the State of Pennsylvania to continue to carry out delimiting surveys around the affected area, and an investigation was conducted to determine the origin or nursery source of the affected trees and evaluate the immediate area for other possible pathways through which EAB may have been introduced. Four counties in Pennsylvania (Butler, Allegheny, Lawrence, and Beaver) will be quarantined for the pest.
In October 2007, an EAB larva was discovered in a West Virginia Department of Agriculture detection tree located in Fayette County. It is believed that the pest arrived in firewood that was illegally transported by tourists visiting the New River Gorge area.
This non-native pest poses an enormous threat to our urban and rural forests. EAB kills healthy trees and is so aggressive that ash trees may die within two or three years after they become infested with the beetle. If it is not contained and eradicated, the impact of Emerald Ash Borer beetle attacks on ash in North America will be similar to that of the devastation from two fungal diseases, Chestnut Blight and Dutch Elm Disease, which destroyed woodland and urban forests in the 20th century.
Importance of the Emerald Ash Borer
Emerald ash borer is a serious pest of quarantine significance. Larvae feed in the phloem and outer sapwood, producing galleries that eventually girdle and kill branches as well as entire trees. This invasive pest has had a devastating impact on communities that now face tremendous tree removal costs associated with dead or dying ash trees that pose a public safety threat.
Ash trees are important to wildlife species because of their seed production. Ash wood is also valued for flooring, furniture, sports equipment (baseball bats, hockey sticks), tool handles, and numerous items requiring strong, hard wood with less rigidity than maple. These trees are as important ecologically in the forests of the northeastern United States and eastern Canada, as they are economically. They are sought out for urban tree planting, partly because they are not defoliated by the (exotic) gypsy moth.
Other repercussions include decreased property values, losses in long-term supply of ash wood, decreased air quality, increased electricity use during hot weather, and impacts on Native American cultures that use ash wood for traditional crafts and ceremonies. In addition, there are other negative impacts on wildlife and natural ecosystems. As a vital component of forest succession, ash colonizes and stabilizes disturbed areas. Ash also is one of the few native trees able to out-compete weeds that prevent most other species from getting established.
States which become infested could lose billions of dollars in forest products, and quarantines imposed by state and federal agencies may have dire consequences for plant and wood products industries. Severe damage would also occur within the tourist industry.
Exotic 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.
Biology
Mating occurs during the first 7-10 days after emergence, with females mating multiple times. Each female lays an average of 77 eggs in bark crevices from late May through July, and these hatch in 7 to 9 days. Larvae tunnel in the cambial layer, feeding on the phloem and outer sapwood, and move into the sapwood as they increase in size. Larva feed aggressively until cooler fall temperatures arrive, and then over winter in the tree. Pupation occurs in late April to June. The pupal chamber is constructed by tunneling into the sapwood at a shallow angle. Newly-formed adults remain in their pupal chambers for 8-15 days, then bore through the bark to the outside.
Adults emerge in mid-May, peaking in late June and may continue emerging as late as mid and late July. 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.
Hosts
In the United States and Canada only ash trees (Fraxinus spp.) appear to be affected. Ash trees are widespread in Canada and the United States. 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 urban landscape. The national urban impact from EAB could exceed $20 billion. Healthy ash trees of any size (from as little as 5 cm in diameter) can be affected.
Chinese scientists report that EAB can also attack trees in the genus Ulmus (elm), Juglans (walnut and butternut), and Pterocarya (wingnut). Pterocarya species are not native to North America but are in the same family as walnuts, pecans, and hickories (genus Carya). One trait common to all these genera is that the wood is ring porous. So far, only ash trees have been infested in North America, even in mixed stands of ash and American elm.
Distribution
Emerald ash borer occurs in China, Mongolia, Inner Mongolia, Korea, Japan, Taiwan and the Russian Far East.
In North America, EAB currently has infestations in Michigan, Ohio, Indiana, Illinois, and Maryland, as well as Windsor, Ontario, Canada.
Symptoms
Symptoms of the ash decline/borer complex include:
- Initial thinning or yellowing of the foliage (general or limited to certain branches).
- 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, are probably present in multiple year infestations.
- Larval galleries--typical galleries meander, bending suddenly, and are packed with frass.