YOUR GARDEN — Plant Information

Pests, Problems, and Diseases

Emerald Ash Borer

HISTORY

The emerald ash borer was first discovered in the United States near Detroit, Michigan, in the summer of 2002. Horticulturalists were puzzled by the sudden decline and loss of hundreds of ash trees and determined their cause of death was attributed to a nonnative, highly destructive beetle, Agrilus planipennis, commonly called Emerald Ash Borer (EAB). EAB originated in Asia and most likely entered the United States in packing materials, such as wooden crates made out of ash. It is now believed that the emerald ash borer has been in the United States since 1990 or 1991. EAB was discovered in Illinois in June 2006, and as of August 2011, was found in 15 states across the country, as well as in Canada. Tens of millions of ash trees have been lost due to this invasive beetle.

Emerald ash borer larvae

Emerald ash borer

BIOLOGY & LIFE CYCLE

Adult beetles are elongated, approximately 1/8 to ½ inches long, and have metallic green wings with bronze bodies. EAB adults begin to emerge from ash trees as the weather warms in the spring and can continue emerging through August, Higher numbers are normally seen in June and early July. Adult beetles usually live for approximately three weeks. Beetles will hide in bark crevices and will occasionally feed on ash foliage, leaving small holes along leaf margins.

Shortly after emergence, adult beetles mate and lay eggs on the bark of ash trees (Fraxinus spp.) that are at least 1½ to 2 inches in diameter. Females will mate multiple times and can lay 60 to 90 eggs during their lifetime. Eggs hatch in approximately seven to ten days. After hatching, larvae chew their way through the tree´s bark and tunnel into the cambium layer where they continue their development. The larvae create serpentine galleries that affect the tree´s nutrient and water transportation system, causing it to decline and eventually die. The larvae overwinter in the tree and pupate in the spring as the weather warms. Research is currently being conducted to determine if larvae produced by late-emerging adults remain in trees for an additional year.

Adult beetles are capable of flying approximately ½ mile from infestation sites. However, they can travel much longer distances through the transportation of infested firewood and nursery stock.

Ash bark

Ash bark damage

DETECTION

Emerald ash borer is difficult, if not impossible, to detect in low-level infestations. The only certain way to confirm EAB is the presence of larva. The observation of one or more of the following warrants further investigation:

Positive ash tree identification (all Fraxinus species are susceptible)
If in doubt, visit Plant Information Service for positive tree identification.

D-shaped holes
As adults emerge in the spring, they leave distinctive D-shaped holes in tree branches and trunks that are approximately 1/8 inch in diameter. The holes may not be visible on the lower trunk or branches of the tree in less severe or recent infestations. Also, they can be difficult to detect in deeply furrowed, thick bark. The tree may require climbing in the upper canopy where bark isn’t as thick for detection of the D-shaped holes. The absence of D-shaped holes does not mean that the tree is not infested.

Tree canopy dieback
EAB usually attacks the tops of trees first and proceeds downward. Most often, the tops of trees experience the worst dieback, but this is not always the case. Infested trees have been known to have sporadic dieback throughout the tree.

Woodpecker damage
Woodpeckers often feed on the outer bark of EAB-infested trees, resulting in a “scraped” look.
Trees infested with EAB are generally stressed due to damage and may produce epicormic shoots either at the base of the trunk or in small amounts on the main trunk.

Splitting bark
Tree bark may split vertically on trees infested with EAB as a result of larval feeding galleries, oftentimes revealing tunnels beneath.

Larval tunneling
EAB-infested trees will exhibit larval tunneling beneath the bark.

PURPLE TRAPS

The use of purple traps is an important tool in the early detection of the emerald ash borer. Purple traps are hung in various locations throughout the state approximately 12 to 15 feet above the ground. They have three sides and are baited with oil from the manuka tree. The oil of manuka trees greatly resembles the volatile oils of ash trees (Fraxinus spp.) and attracts adult emerald ash borers. The traps are covered with a sticky gluelike substance that traps the beetles when they land on the trap. The traps are extremely useful in determining whether given areas have been infested and deciding upon management treatment options.

management

Chicago Botanic Garden Emerald Ash Borer Management Plan

PHOTO: emerald ash borer

Since 2002, when EAB was first detected, many municipalities have removed most ash trees to reduce monetary impacts, financial restrictions, and labor intensities. Other municipalities limit ash tree removal to infested trees only.

Government quarantines play an integral role in preventing EAB from spreading. The USDA Animal & Plant Inspection Service (APHIS) has federally restricted the movement of all ash products outside of the state of Illinois. Refer to www.aphis.usda.gov/plant_health/plant_pest_info/emerald_ash_b/index.shtml for up-to-date federal news releases. The Illinois Department of Agriculture has established quarantine zones throughout the state that regulates restricted articles, consisting of all ash tree species, EAB adults and larvae, branches, lumber, firewood, nursery stock, roots, green lumber, as well as composted and uncomposted wood chips The restricted articles also include all hardwood firewood, such as hickory, maple, and oak. Refer to www.agr.state.il.us/eab/index.php for up-to-date Illinois Department of Agriculture news releases.
In addition, the Illinois Department of Natural Resources (IDNR) prohibits transporting firewood that originated in a quarantined area to any state park, fish and wildlife area, natural area, campground, recreation area, or other property owned or managed by the IDNR.

As ash trees across the U.S. continue to be removed as a result of emerald ash borer infestations, homeowners are turning to sawmills in order to reuse the lumber. A list of arborists, sawyers, and woodworkers can be found on the Illinois Emerald Ash Borer Wood Utilization Team website at www.illinoisurbanwood.org/sawyers.html.

CHEMICAL TREATMENT

The effectiveness of insecticides continues to be researched and at present, there are no known chemicals that will cure an infested tree. Insecticide treatments are only used as preventatives, with the hope of extending the life of the tree, giving the owner time to plan for their ash removal and replacement. Better control using insecticides is evident with smaller trees, with trunk diameters of less than ten inches. Insecticide treatments should not be considered further away than 10 to 12 miles of known infestations. Several factors can determine the effectiveness of chemical treatments, including the original health and diameter of the tree, as well as timing of treatments. The cost benefits of annual treatment vs. removal and planting should be considered before deciding on the use of chemicals. Please call the Plant Information Service at (847) 835-0972 for approved insecticidal control options.

State-Wide Quarantine Enacted to Fight the Emerald Ash Borer

On November 21, 2006, the USDA's Animal and Plant Health Inspection Service announced the expansion of its Emerald Ash Borer (EAB) quarantine to include the entire states of Illinois, Indiana, and Ohio — more than doubling the previously quarantined area. With 14 states and two Canadian provinces now infested with emerald ash borer, it's no wonder property owners are worried.

Research is being conducted at universities to understand the beetle's life cycle and find ways to detect new infestations, control EAB adults and larvae, and contain the infestation.

Quarantines are in place to prevent infested ash firewood, logs, or nursery trees from being transported and starting new infestations.

What to know about EAB:

It attacks only ash trees (Fraxinus spp.).
Adult beetles are metallic green and about ½ inch long.
Adults leave a D-shaped exit hole in the bark when they emerge in spring.
Woodpeckers like EAB larvae; heavy woodpecker damage on ash trees may be a sign of infestation.
Firewood cannot be moved in many areas of Michigan, Illinois, Indiana, Maryland, Minnesota, Missouri, New York, Ohio, Ontario, Pennsylvania, Virginia, West Virginia, and Wisconsin because of the EAB quarantine.
It probably came from Asia in wood packing material.

For more information, visit www.emeraldashborer.info. Much of the information on this web page comes from this website, part of a multinational effort in Illinois, Indiana, Michigan, Iowa, Kentucky, Maryland, Minnesota, Missouri, New York, Ohio, Pennsylvania, Virginia, West Virginia, Wisconsin, Ontario, and Quebec to bring you the latest information about emerald ash borer.

Also, researchers and specialists from Ohio, Michigan, Indiana, Wisconsin, and Illinois have developed a publication for property owners that addresses various methods to treat ash trees for the pest. For a hard copy of this publication, Insecticide Options for Protecting Ash Trees from Emerald Ash Borer, call (517) 353-6740 at Michigan State University, and ask for bulletin number E3075.

Please contact Plant Information Service at (847) 835-0972 or via e-mail at plantinfo@chicagobotanic.org for more information.