Invasive Species Council of Manitoba

Emerald Ash Borer(Agrilus planipennis )

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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.


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 Mayto 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.


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.

Information provided courtesty of the Ontario Federation of Anglers and Hunters and more information is available on their website.

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