The Emerald Ash Borer
"The Green Menace"
The Threat
The emerald ash borer (EAB) is a very small but very destructive beetle. Metallic green in color, its slender body measures 1/2 inch in length and 1/8 inch wide. The average adult beetle can easily fit on a penny.
Native to China and Eastern Asia, the EAB probably landed in North America hidden in wood packing materials commonly used to ship consumer goods, auto parts, and the like. Although no one can say for sure when EAB arrived in southeastern Michigan, the scientific community believes the beetle went undetcted for 5 o 7 years, based on its widespread distribution and destrction. EAB was officially identified in the summer of 2002.
This beetle is currently known to be responsible for the death or decline of more than 6 million ash trees in a 13-county area around detroit. EAB has also impacted various communities in Essex County, Ontario, and the Canadian city of Windsor, across the Detroit River. Canadian officials estimate that between 100,000 and 200,000 ash trees are infested.Although large EAB infestations are concentrated in Michigan and parts of Canada, the States of Ohio, Maryland, Indiana, and Virginia have also found EAB in smaller, somewhat contained areas.
In terms of the range and extent of the EAB infestation in North America, the human element is of particular significance. Unknowingly, people's behaviors associated with everyday living and commerce have greatly contributed to the spread of the EAB. The movement of any ash tree products (e.g. branches, logs, wood chips larger than 1 inch, nursery stock, and firewood) advances the spread of EAB. Thus, human behavior is a defining factor in the spread of EAB.
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Scientifically Speaking
Entomologists from the United States and Canada have been studying the EAB to learn more about its biology and behavior. Because this pest has never been found anywhere in North America prior to the current infestation, this information is continually being updated.
Scientists have discovered that the beetle has a 1-year life cycle. From May to August, adults emerge from overwintering sites under bark and mate. Females lay eggs in bark crevices, and the eggs hatch in about 10 days. The eggs develop into wormlike larvae, which tunnel under the bark to feed and grow throughout the fall. The activity eventually kills the tree. Larvae lie dormant during the winter and emerge from trees in May as adults, leaving a unique D-shaped exit hole.
Here are some key discoveries about the EAB:
- On this continent, EAB attacks only ash trees, and all the ashes - white, black, and green, etc. - are at risk except the mountain ashes.
- EAB is a good flyer but tends to fly only relatively short distances (about 1/2 mile)
- We cannot count on natural predation to control EAB: the beetle has no known predators in North America, although woodpeckers will eat them.
- EAB infestation is always fatal to ash trees. Infested trees will decline from the top down and will be dead in 1 to 3 years, even if the trees were healthy before being attacked by EAB.
It is extremely difficult to determine whether an ash tree is infested or not infested with EAB because tree decline is usually gradual. Early symptoms of an infestation might include dead branches near the top of a tree or perhaps wild, leafy shoots growing out from its lower trunk. D-shaped tunnels are significant signs of EAB.
If a tree is infested with the EAB, tree removal is recommended as the most effective way to eliminate these exotic pests and prevent the species' further spread. By felling a tree and chipping it into pieces 1 inch across or smaller, no viable larvae will remain.
Treatment options may eventually be approved for some homeowners living in a generally infested area where suppression efforts are being used, with the understanding that treatments are not a cure. At best, a homeowner might only prolong a tree's decline. Every EAB-infested tree will die.
Cooperation is Key
The public at large is esential to eliminate this pest. Below are some things you can do now to lessen the likelihood of EAB's becoming established in the United States.
- Don't move firewood. Humans unknowingly contribute to the spread of EAB when they move firewood. Eab larvae can survive hidden under the bark of firewood. Play it safe: don't move any firewood and you won't move any beetles.
- Visually inspect your trees. Early detection is a key factor. If trees display any sign or symptom of EAB infestation, contat your State agriculture agency.
- Spread the word. Talk to your neighbors, friends, and coworkers and get them onboard. Public awareness and education is an ongoing process; support the effort.
- Know State and Federal regulations. Make sure you understand the regulations that govern your own State and those States and Provinces you may visit.
- Ask questions. If you receive ash nursery stock, know it's origin and your supplier. EAB larvae may be hiding under the tree bark.
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*All information and images courtesy of the USDA (Program Aid No. 1769)
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