Emerald Ash Borer in Michigan
Sarah Brodeur Campbell, 18 December 2003.
The emerald ash borer (Agrilus planipennis Fairmaire,
is an introduced pest
from Asia, which has recently been discovered in
several counties in Michigan, two Ohio counties, and one county in Canada. This
leaflet is intended for the general public in Michigan. It
is to serve as a recognition guide for identifying the emerald ash borer. Since the range of the emerald ash borer
within the United States and much information associated with the
life cycle of this insect is not yet certain, individuals finding this species
should contact their local Forest Service office or a local Department of
Adult beetles are a dark metallic green color
and are roughly a half inch long and 1/16 inch wide. Adult females are larger in size than
males. Both sexes have narrow, elongated
bodies and are hairless. The surface of
the wing cases is metallic green, and the body is either brassy or golden
green. When the wings are spread, the
top of the abdomen usually covered by the wings is a metallic coppery red. The head of the beetle is somewhat smaller
than the upper thorax and wing cases, which are the
same size. The covering on the upper
thorax is sculpted and wavy, and the wing cases are rough and grainy. The tips of the wing cases are rounded and
the edges have small toothlike projections.
Adult beetles are both larger and greener than native related species,
like the bronze birch borer.
Adults are typically seen on or near infested trees
and are active during the daytime, preferring warm, sunny days. On hot days (above 32°C or 90°F) or on windy or rainy days they are found sheltering
in bark crevices or foliage. If they are
disturbed, adult beetles will fall to the ground and feign death.
Larvae are a creamy white color. They are usually 26-32 cm
when full grown,
and are flattened from the top to the
bottom. The abdomen has 10
segments. The last abdominal segment has
a pair of brown appendages shaped like pincers.
The head, which is brown, is usually not visible except for the
mouthparts. Pupae are also creamy white.
Larvae and pupae are found under the bark of infested trees.
EAB (Bottom view)
Eggs are light yellow and oval, turning
brownish yellow before they hatch. The
center of each egg is slightly convex.
Eggs are 0.6 mm in size and found on the bark surface or in bark
crevices on ash trees.
Range and Hosts
ash borer is originally from an area in Asia encompassing northeastern China,
and the Russian Far East. In its native
range, the beetle feeds on a variety of hardwood trees, such as Chinese ash (F. chinensis).
The emerald ash borer has been
discovered in several counties in southeastern Michigan and two counties in
Ohio, Essex County, Ontario, and Prince George’s County, Maryland. The quarantined counties in Michigan
are Monroe, Lenawee, Wayne,
Washtenaw, Livingston, Lapeer, St. Clair, Genesee,
Ingham, Jackson, and Shiawassee, as
of August 2003. The emerald ash borer
has also been discovered in isolated pockets in Eaton,
Kent, and Saginaw
counties of Michigan, as of
August 2003, with another possible infestation in Ottawa
County. In February 2003, the emerald ash borer was
discovered in Lucas County, Ohio, and has since been found in Defiance County, Ohio,
only two miles from the Indiana
border. In September 2003, emerald ash borers were positively identified in
nursery trees in Maryland, and
the infested trees were destroyed.
Although it was not discovered in Michigan
until 2002, evidence was found to suggest that the species has been present in
those areas for at least 5 years. In Michigan,
it has only been observed feeding on white, green, and black ash (Fraxinus americana, F. pennsylvanica, and F. nigra) as well as several varieties
of horticultural ash. Appendix 2 gives a
map indicting the range of Fraxinus (Ash) species in the northern
US. This species of beetle can kill trees
of all sizes. Stress, such as from
drought, can make ash trees more vulnerable to the emerald ash borer, but
vigorous trees undergoing regular watering and fertilization have also been
borers have a one to two-year life cycle in Michigan. In southern Michigan,
their life cycle is only one year, with larvae overwintering as full-grown
larvae, but they can overwinter for 2 years as larvae in colder regions. Little is know about
the life cycle of the emerald ash borer in the US,
but work on this subject is ongoing at the North Central Research Station of
the US Forest Service.
beetles emerge from mid-May to late June.
Males live for approximately 13 days, and female adults live for
approximately 22 days. The females can
mate several times and lay eggs around 7-9 days after mating. A single female lays 65-90 eggs in her
lifetime, which are individually deposited on the bark surface or in bark
crevices of the ash tree trunk or branches.
Eggs are usually deposited on the sunny side of the tree. Egg laying can take
place from late May to early August in Michigan.
7-10 days after oviposition, and the emerging larvae tunnel into the cambial
region of the host tree. They feed on
the phloem and sapwood, creating flat, wide tunnels that zigzag to create a
distinctive S-shape. The feeding gallery
widens with the growth of the larva, and is generally 20-30 cm in length. The galley is typically filled with fine
frass and sawdust.
overwinter as full-grown larvae, creating a shallow chamber in the sapwood for
this purpose. They pupate in late April
to early May. Newly hatched adults
remain in the chamber for approximately 1-2 weeks to allow their exoskeletons
to properly harden. Then they bore a
D-shaped exit hole through the bark of the tree and emerge headfirst.
through their lifetimes on the foliage of ash trees, typically consuming 0.45
cm^2 a day. Feeding by adults leaves irregularly shaped leaves with jagged
edges. While the beetles usually only
fly locally, they can disperse a few kilometers by flight, usually in search of
new host trees.
source of movement for the species is anthropogenic. Any life stage of the emerald ash borer can
be moved in raw wood with bark. For
example, eggs, larvae, or adult beetles can be moved in firewood, lumber with
attached bark, or nursery trees.
dieback is usually the first symptom of infestation, as the presence of emerald
ash borers is difficult to detect.
D-shaped exit holes are present on the branches and trunk of infested
trees after the first year of infestation.
Trees may also produce calluses over feeding galleries, which may cause
5-10 cm vertical splits in the bark.
branches die when feeding tunnels completely encircle (girdle) the branch. In the first year of infestation, trees may
lose 30-50% of the canopy, and 2-3 years of infestation often kills trees. Dense shoots may appear on the trunk at the
boundary between living and dead tissue, and are also produced by the roots.
a tree has been infested for 1-2 years, bark may fall off the infested trunk or
branches, showing the distinctive feeding galleries in the sapwood. This bark sloughing, along with crown dieback
and shoot production are the principal signs that a tree is infested with
emerald ash borers.
hairy woodpeckers are frequently observed feeding on infested trees, eating the
Not much is
known about this insect in North America. Currently, studies are underway at the North
Central Research Station of the US Forest Service investigating infested
firewood, insecticide application, natural enemies, seasonal development of the
emerald ash borer in North America, trapping and
monitoring, and within tree distribution of the insect. Hopefully, surveying and control programs for
the emerald ash borer will be developed from this research. Biological control is one method of control
promising hope, as researchers are investigating natural enemies from the
insect’s home range.
Ash is a
common species in both natural and urban forests in the US
and Canada. It is widely planted as a shade tree in urban
areas, and provided more than 149 million cubic feet of timber products in the US
in 2001. On 16 July 2002, ash trees and ash wood products
were quarantined in the state of Michigan,
with the intent of limiting the spread of the beetle through human assistance.
trees within the quarantined counties in Michigan
(see Range) need to be considered for management at this time. Insecticide will probably not help infested
trees, as the internal damage to sapwood may be too great for the tree to
recover. Insecticides may, however, work
to protect healthy trees from infestation.
Trees that are treated with preventative insecticides, such as
imidacloprid, bidrin, or contact insecticides, need to be treated on a yearly
basis. It is best if trees are treated
by arborists rather than by homeowners.
As always, all insecticides and pesticides should be applied in
accordance with their labels. Trees that
are watered and fertilized on a regular basis will be less stressed and
therefore possibly less susceptible to attack.
treatment for infested trees is to remove them.
After removal, infested trees need to be chipped, de-barked, or
burned. This should be done before May,
in order to prevent adult beetles from emerging. Marshalling centers have been set up in
infested counties to provide no-cost disposal of ash wood.
possibility in place of management is to plant alternative tree species in
infested areas where emerald ash borer will become a problem. The emerald ash borer has been known to only
kill ash trees in Michigan. Therefore, planting alternative species in
cities, towns, and at homes will limit the available host trees for the emerald
Department of Agriculture. Site accessed 05 Sept 2003. http://www.na.fs.fed.us/spfo/eab/images2/riskmap.html
- USDA. Site accessed 05 Sept 2003.
DG & Russell, H. Dec.
Alert: Emerald Ash Borer. USDA
Forest Service, Northeastern
photos used in this pest leaflet are courtesy of the USDA. Site accessed 05 Sept 2003.
Food Inspection Agency Science Branch.
Site accessed 05 Sept 2003. Agrilus
planipennis Fairmaire: Emerald Ash Borer. http://www.inspection.gc.ca/english/sci/surv/data/agrplae.shtml
North Central Research Station.
Site accessed 05 Sept 2003
and 21 Nov 2003. http://www.ncrs.fs.fed.us/4501/eab/index.html
of the Michigan
Entomological Society. Sept
2002. The Emerald Ash Borer: A New
Exotic Pest in North America.
JD et al. Aug. 2002. Ash Pests. Bugwood.
Site accessed 05 Sept 2003. Http://www.forestpests.org/ash/ashpests.html
D & McCullough, D. March
2003. What Can Homeowners do to
Protect Their Trees from the Emerald Ash Borer? Michigan
- Linsmeier-Wurfel, S.
31 July 2003. “Isolated pocket of Emerald Ash Borer
Confirmed in Kent County: Survey to begin at Wyoming
location to determine extent of infestation.” Http://www.michigan.gov/minewswire/.
- Linsmeier-Wurfel, S.
5 August 2003. “State takes additional Emerald Ash
Borer control steps: Quarantine
transport of ash nursery stock banned in Lower Peninsula.” Http://www.michigan.gov/minewswire/.
Department of Agriculture. 15
August 2003. Fact
Sheet: Emerald Ash Borer in Ohio. http://www.state.oh.us/agr/COMM-facts-eab-8152003.html
Dept. of Agriculture News Release. 02 September 2003. “New Exotic Pest Identified in Maryland’s
Ash Trees.” http://www.mda.state.md.us/press/eabrel.html.