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Emerald Ash Borer

Emerald Ash Borer (Agrilus planipennis) By Milka Hider

Relatively new to North America, the Emerald Ash Borer is believed to have been accidentally introduced in 2002 inside wood packing material imported from eastern Asia (MNR, 2010). The beetle has spread mostly through the human movement of infested materials such as dead ash logs, firewood and nursery stock from infested areas (Canadian Food Inspection Agency [CFIA], 2012) as well as through flight. Left unchecked, this highly invasive beetle has the potential to kill most of the 7.5 billion ash trees throughout North America (Golowenski, 2012). This insect attacks and kills all North American species of ash (Fraxinus spp.) (Ministry of Natural Resources [MNR], 2010) and, thus far, has destroyed millions of ash trees since its introduction to the United States and Canada. In order to preserve the ash population, and its ecological benefits to both our urban and forested areas in Canada an understanding of the lifecycle, identification, and possible control measures of the Emerald Ash Borer are necessary.

Early detection of the Emerald Ash Borer is very difficult as the eggs, which are deposited on the bark, are almost undetectable. The eggs are approximately one millimetre long and 0.6 millimetre in diameter (MNR, 2010). When hatched, the larvae bore through the bark and feed on the phloem and outer layer of new sapwood (MNR, 2010) where they remain and engage their developmental stages up to and including the adult stage. The larvae’s tunnelling movements destroy the phloem, effectively cutting off the transport of nutrients and water up and down the tree eventually killing the tree. An adult beetle is metallic green in colour and is 8.5 to 14.0 millimetres long and 3.1 to 3.4 millimetres wide. An infected tree is usually found in its second or third year of infestation which is evidenced by a dramatic loss of leaves in the crown and often a sudden profuse growth in long shoots at the base of the tree (Ontario Wood Lot Association, 2004). Further signs of an infected tree are cracks in the bark that appear as vertical splits, increased woodpecker activity trying to feed on the larvae under the bark, and exit holes which are distinctly D-shaped and are 3.5 to 4.0 millimetres across through which the adult beetles emerge. (University of Maryland, 2012)

Until more scientific knowledge is available, the greatest control measure to stop the spread of the Emerald Ash Borer is to regulate and/or restrict the movement of infested ash firewood, logs, and nursery stock. The Canadian Food Inspection Agency in partnership with other federal, provincial, and municipal governments is responsible for the eradication or control of plant pests that have been introduced to Canada. Once the Emerald Ash Borer was identified in Ontario, the Canadian Food Inspection Agency took the following immediate actions and issued government orders restricting the movement of infected materials and quarantined infected areas. The agency participated in the cutting and burning of ash trees that were in advanced stages of infestation and introduced compensation programs for tree replacement. They created a massive public awareness program with education on how to identify infected trees and the beetle itself. The plant industry and scientific communities were informed with information about the pest and insecticides that have been successfully applied to infected trees (CFIA, 2012).

The greatest challenge facing scientists working to stop the destruction of this insect is to discover a means of very early identification of infestation. Developing new survey methods, studying biological control through the use of pathogens and parasitoids (MNR, 2012), and studies of the beetle’s life cycle, feeding habits and host tree selection will provide the research needed to overcome this hurdle. Increased public awareness and the development of new effective and ecologically friendly insecticides will provide the vehicle necessary to control and eventually diminish the devastation of the Canadian Ash population.


Canadian Food Inspection Agency (May, 2012). Plant Protection, Insects, Emerald Ash Borer. Retrieved from borer/eng/1337273882117/1337273975030

Golowenski, D. (2012, October 21). Ash Trees Continue Road to Extinction, The Columbus Dispatch. Retrieved from to-extinction.html

Ministry of Natural Resources (January, 2010). Forest Health, Emerald Ash Borer.
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Ministry of Natural Resources (September, 2012) Emerald Ash Borer. Retrieved from

Ontario Woodlot Association (February, 2004). The Emerald Ash Borer, A Tiny killer of Ash Trees Hits Southwestern Ontario.

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University of Maryland (October, 2012). Home and Garden Information Center, Emerald Ash Borer. Retrieved from