Emerald Ash Borer in Michigan

Information Sheet

Sarah Brodeur Campbell, 18 December 2003.

The emerald ash borer (Agrilus planipennis Fairmaire, Coleoptera: Buprestidae)

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 Agriculture office.

Identification

Adult EAB

A. Storer, MTU

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.

Adult EAB J.W. Smith

Larvae are a creamy white color. They are usually 26-32 cm when full grown,

Adult EAB (Bottom view)

J.W. Smith

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.

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.

Larval instars

D. Cappaert

Range and Hosts

The emerald ash borer is originally from an area in Asia encompassing northeastern China, Korea, Taiwan, Mongolia, Japan, 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, Oakland, Macomb, 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 killed.

Life History

Emerald ash 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.

Adult 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.

Galleries

A. Storer

MTU

Eggs hatch 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.

The larvae 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.

Adults feed 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.

One main 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.

Symptoms

Canopy 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.

D-Shaped Exit Hole

D. McCullough, MSU

Canopy 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.

After 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.

Downy and hairy woodpeckers are frequently observed feeding on infested trees, eating the larvae.

Ash Decline

J.W. Smith

Woodpecker Attacks

D. Cappaert

Gallery and Sprouts

J. W. Smith

Bark Fissure

J. W. Smith

Management

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.

Only ash 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.

The best 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.

A 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 ash borer.

References:

1. Michigan Department of Agriculture. Site accessed 05 Sept 2003. http://www.na.fs.fed.us/spfo/eab/images2/riskmap.html
2. USDA. Site accessed 05 Sept 2003. http://www.ncrs.fs.fed.us/4501/eab/maps.html
3. McCullough, DG & Russell, H. Dec. 2002. Pest Alert: Emerald Ash Borer. USDA Forest Service, Northeastern Area.
4. All photos used in this pest leaflet are courtesy of the USDA. Site accessed 05 Sept 2003. http://www.na.fs.fed.us/spfo/eab/img/img.html
5. Canadian 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
6. USDA North Central Research Station. Site accessed 05 Sept 2003 and 21 Nov 2003. http://www.ncrs.fs.fed.us/4501/eab/index.html
7. Newsletter of the Michigan Entomological Society. Sept 2002. The Emerald Ash Borer: A New Exotic Pest in North America. 47: 3-4.
8. Solomon, JD et al. Aug. 2002. Ash Pests. Bugwood. Site accessed 05 Sept 2003. Http://www.forestpests.org/ash/ashpests.html
9. Smitley, D & McCullough, D. March 2003. What Can Homeowners do to Protect Their Trees from the Emerald Ash Borer? Michigan State University.
10. 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/.
11. Linsmeier-Wurfel, S. 5 August 2003. “State takes additional Emerald Ash Borer control steps: Quarantine expanded; sale, transport of ash nursery stock banned in Lower Peninsula.” Http://www.michigan.gov/minewswire/.
12. Ohio Department of Agriculture. 15 August 2003. Fact Sheet: Emerald Ash Borer in Ohio. http://www.state.oh.us/agr/COMM-facts-eab-8152003.html
13. Maryland 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.