What is an Emerald Ash Borer?

 Larva of the emerald ash borer (David Cappaert, Michigan State University)

Origin and Description of the Emerald Ash Borer

The emerald ash borer (EAB) is a small beetle, measuring 8.5 to 13.5 mm long by 3 mm wide. It has a metallic green-blue colour with iridescent highlights. This insect, native to Asia, is thought to have been transported to North America in infested wood or wooden pallets.

he adult feeds on ash leaves and lays its eggs under the tree's bark. The segmented white larvae feed on the cambium, the layer under the bark, and form trenches (galleries) which prevent nutrient circulation, causing the death of the tree. Once mature, the larvae metamorphose into adult borers who initiate the next egg-laying cycle.

The adult insect can be observed in the months of June through August, during which it emerges and reproduces.

Impact of the Emerald Ash Borer

This insect feeds exclusively on ash trees of the genus fraxinus in any of its varieties. In general, an infested tree dies in two or three years, as the larvae and their descendants feed on it year after year. It is important to know that the insect can be present in the tree for several years before the first visible signs of infestation appear.

Since 2002, this pest has killed more than 20 million ash trees in North America. This tree occupies an important place in Quebec's unspoiled environments and its cities. Strong yet flexible, its wood is used to manufacture many sturdy objects including furniture and floors, which gives it a significant economic value. Thus, the presence of this beetle represents a real threat to the environment and the economy if no action is taken to curb its spread.

How is it spread?

The emerald ash borer propagates in two ways:
  • The first is natural and of little concern, because the EAB only moves when it lacks food. It typically flies 10-12 metres on average. However, it is apparently capable of flying up to 10 kilometers in search of food. 
  • The second way is through human activity, including the transport of wood products and waste from felling trees infested by the insect. The latter is the main reason for the rapid dispersion of the emerald ash borer.