The Emerald Ash Borer (EAB) is an invasive insect native to eastern Asia that attacks and eventually destroys healthy ash trees (Fraxinus spp.). It was discovered in 2002 in Michigan and Ontario and likely came here in a shipment of untreated wooden packing material from Asia.

Characteristics

The adult EAB is a long, slender insect with dark, metallic green coloured wings on top fading to a lighter, metallic brassy green colour on the rest of its body. It ranges in size from 8.5-14 mm (.3 - .6 in) with the females being slightly larger than the males. The larvae are creamy white in colour with a light brown head. The larval body is flattened and has ten segments with a pair of pincers on the last segment.

The adult EAB emerge from D-shaped holes it has made in the tree between mid May to late June. The adults are most active during the summer on calm, sunny days and tend to seek shelter in bark crevices on cooler, windy, rainy days or very hot days. They are strong flyers and experts propose ash-free zones as wide as 10 kms to prevent their spread. Adults feed on the leaves of the ash trees producing irregular shape patches with jagged edges. The adults mate and females produce anywhere from 65-90 eggs during its life cycle.

Eggs are deposited in the trunk and branches of a tree in among the cracks and crevices of the bark. The eggs generally hatch within 1-2 weeks and the larvae burrow in through the bark of the tree to the cambial layer. The larvae feed in this layer producing S-shaped tunnels that eventually girdle the tree. The larvae over-winter and in April the pupal stage begins and adults begin to form in May.

Distribution

The EAB is native to Asia and is found in China, Taiwan, Korea, Japan, Mongolia and eastern Russia. The discovery of EAB in North America was made in 2002 in southeastern Michigan, which shortly after lead to the discovery of EAB in soutwestern Ontario.  It has now been identified in the states of Michigan, Ohio, Indiana, Maryland, Illinois, West Virginia and Pennsylvania.  In Ontario the EAB is believed to have traveled across the Detroit River into the Windsor area.  Infestations were first discovered in Essex County and have since been found in the Municpality of Chatham-Kent, Elgin County, Lambton County and the City of London in Middlesex County.  Most recently an infestation has been detected in the County of Norfolk. 

In 2004 a 10x30km Ash Free Zone was established by the Canadian Food Inspection Agency in the Municipality of Chatham-Kent to slow the spread of the EAB.  Regulations for that zone have since been revoked due to established populations east of this area.

Impact

The tunnels created by the larvae in the cambial layer girdles the tree. Signs that a tree has been infested are apparent when the top of the tree begins to die back and there are much fewer leaves. The tree begins to produce root suckers or long shoots from the trunk of the tree. There are small D-shaped holes along the trunk where the adults emerged and often there will be cracks in the trunk from tree forming a callus where damage occurs.

The EAB attacks and kills all species of healthy and stressed ash trees within two or three years of infestation. It has killed green ash (Fraxinus pennsylvanica), white ash (Fraxinus americana) and black ash (F. nigra), as well as several horticultural varieties of ash. It could, however, have the greatest impact on blue ash (Fraxinus quadrangulata) and pumpkin ash (Fraxinus profunda) which are considered threatened in the area. EAB does not attack mountain ash (Sorbus spp.) since it is not a true ash.

All ash trees are an important part of the ecosystem providing food and habitat for many species of birds, mammals and insects. Ash also maintain soil structure, healthy watersheds and help clean the air of carbon dioxide and contaminants particularly in urban settings. The loss or decline of ash trees would limit habitat and food for many species and could impact forest and urban biodiversity.

The decline or elimination of ash trees from the North American landscape will have both economic and aesthetic impacts. Many ash trees are found in urban and rural landscapes and mature trees that are lost in these settings will be difficult to replace. Ash trees are a valuable tree in the forest product industry providing valuable timber for furniture, building products, boat building products and recreational products. Ash trees are also important for the nursery trade and their loss could impact this industry since the EAB can be transported on nursery stock.

Prevention

The Candian Food Inspection Agency (CFIA) placed a Infested Places Order for the County of Essex, the Municipality of Chatham-Kent, the County of Elgin, the County of Lambton and Middlesex County. The Infested Places Order restricts the movement of nursery stock, trees, logs, lumber and wood with bark attached, wood chips or bark chips, firewood and all untreated vehicles that were used to carry these articles for all ash species.  Following the new discovery of EAB in Norfolk County a quarantine was put in place within a five-kilometer radius of the infestation.

More information on the EAB can be found on the CFIA's website www.inspection.gc.ca

or the MNR's website: http://ontariosforests.mnr.gov.on.ca/foresthealthoverview.cfm

If you see EAB or signs of infestation call CFIA toll-free at 1-866 463-6017 or

the MNR at 1-800-667-1940.