Figure 2—S-shaped tunnels, made by EAB larvae, 

riddle infested ash trees.

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 now believes the beetle went 

undetected for up to 12 years, based on its widespread distribution and destruction. 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 15 million ash trees 

in a 20-county area around Detroit. EAB has also 

impacted various communities in Ontario, Canada. 

Essex County, across the river from Detroit, was 

declared infested with EAB in 2002. Canadian officials estimate that between 100,000 and 200,000 ash 

trees are infested and will die in Essex. The neighboring county, Chatham–Kent, has recently been declared 

to be infested with EAB.

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, woodchips, nursery stock, and firewood) advances the spread of EAB. Consider this: current research 

suggests that the natural spread or movement of the 

EAB is about 1/2 mile each year. If that estimate is 

accurate and the length of time EAB has been present is 12 years, at press time (April 2005) the generally infested area in Michigan* should cover about 

113 square miles. But as of 2005, Michigan’s generally infested area covers almost 13,000 square miles! 

Human behavior is a defining factor in the spread of 

EAB.

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 being continually updated.

Scientists have discovered that, in a temperate climate, the beetle can develop from egg to adult in as 

little as 1 year. 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. This activity eventually kills 

the tree. Larvae lay 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 

(Fraxinus spp.), and all the ashes—green, white, 

and black, etc.—are at risk except the mountain 

ashes (Sorbus spp.), which are not a true ash.

■ 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.

■ EAB is under a great deal of scientific scrutiny now. 

New information and discoveries will improve 

managers’ ability to detect, control, and eradicate 

the beetle.

Signs and Symptoms

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 exit holes and bark 

splits exposing S-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. Considering the most current science, the 

U.S. Department of Agriculture’s Animal and Plant 

Health Inspection Service recommends felling infested 

trees, chipping them, and burning the chips.

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.

Because new treatment options and methods are 

expected to become available in the future, we encourage homeowners to talk to their local Extension Office 

or State department of agriculture for the most up-todate information.

Figure 1—The adult emerald ash borer, an exotic 

wood-boring beetle, attacks ash trees exclusively.

_________

* These calculations are based on the beetle’s having 

appeared at only one point of introduction.

Figure 3—The D-shaped exit 

hole is a unique signature of 

the EAB.

Figure 4—Epicormic shoots 

are a telltale sign of a tree 

under stress.
The Cooperative Mix

Detection, control, and eradication of EAB is a huge 

undertaking. Cooperation between Federal and State 

government agencies, municipalities, universities, the 

greening industry, and the public at large is essential 

to eliminate this pest.

Here 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, contact 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 its point of origin and your supplier. EAB larvae may be hiding under the tree bark.

The U.S. Department of Agriculture (USDA) prohibits discrimination 

in all its programs and activities on the basis of race, color, national 

origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply 

to all programs.) Persons with disabilities who require alternative 

means for communication of program information (Braille, large 

print, audiotape, etc.) should contact USDA’s TARGET Center at 

(202) 720–2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, 

Office of Civil Rights, Room 326–W, Whitten Building, 14th and 

Independence Avenue, SW, Washington, DC 20250–9410 or call 

(202) 720–5964 (voice and TDD). USDA is an equal opportunity 

provider and employer.

Cover photo: Bark’s-eye view of the emerald ash borer, a 

foreign insect that attacks all species of ash trees except the 

mountain ash, which is not a true ash.

Photo credits: The cover photograph and figure 6 were taken by 

APHIS PPQ employee Dr. James E. Zablotny. APHIS gratefully 

acknowledges the cooperation of Michigan State University’s 

David Cappaert, who supplied the images used in figures 1 and 

5. Those photographs are reproduced by permission. The images 

in figures 2, 3, and 4 were supplied by PPQ employees David R. 

McKay, Brian Sullivan, and James W. Smith, respectively.

Web sites: http://www.aphis.usda.gov

 http://www.na.fs.fed.us/spfo/eab

 http://www.emeraldashborer.info

Issued July 2004

Revised April 2005

United States Department of Agriculture

Animal and Plant Health Inspection Service

Program Aid No. 1769

Emerald 

Ash Borer

The Green Menace Figure 6—The female beetle lays eggs in 

bark crevices of ash trees.

Figure 5—EAB larvae can be transported to new 

locations while hidden under the bark of firewood.

These Web sites offer more-detailed information 

about the EAB.

http://www.aphis.usda.gov

http://www.na.fs.fed.us/spfo/eab

http://www.emeraldashborer.info

Toll-free information line: 1–866–322–4512