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Victoria Day – Monday, May 20. View holiday hours for City of Winnipeg facilities and services.

Victoria Day – Monday, May 20. View holiday hours for City of Winnipeg facilities and services.

Insect Control

Emerald Ash Borer

What does the emerald ash borer look like?

Emerald ash borer

Adult beetles are metallic blue-green, narrow, hairless, elongate, 8.5 to 14.0 mm long and 3.1 to 3.4 mm wide. The head is flat and the vertex is shield-shaped. The eyes are bronze or black and kidney shaped. The prothorax is slightly wider than the head and is transversely rectangular, but is the same width as the anterior margin of the elytra. The posterior margins of the elytra are round and obtuse with small tooth-like projections on the edge. Mature larvae are 26 to 32 mm long and creamy white. The body is flat and broad shaped. The posterior ends of some segments are bell-shaped. The abdomen is 10-segmented. The 1st 8 segments each have one pair of spiracles and the last segment has one pair of brownish, pincer-like appendages.

What does EAB damage look like?

Immature beetles maturation feed on host tree foliage, creating irregular notches in the leaves. Eggs are laid singly on the bole or branches. First instar larvae bore through the bark and feed on the inner bark and the outer sapwood, eventually forming flat and wide (6 mm), "S-shaped" galleries that are filled with a fine brownish frass. Galleries are 9 to 16 cm long (up to 20 to 30 cm) and increase in width from the beginning to the end. Galleries can occur along the entire bole and in branches that are at least 2.5 cm in diameter. Callus tissue may be produced by the tree in response to larval feeding and may cause vertical bark cracks to occur over a gallery.

Pupation takes place at the end of a gallery just beneath the bark, or near the surface of the sapwood (5 to 10 mm) and even in the corky tissue of thick-barked trees. Beetles emerge through "D-shaped" exit holes, 3.5 by 4.1 mm in size. These holes are very difficult to find so careful inspection is required. Woodpecker activity may also indicate the presence of this beetle. Dying or dead trees, particularly with bark sloughing off and crown die-back can also be used as indicators of attack. Other signs of attack include a thinning crown, epicormic shoots, and vertical cracks on the trunk.

How can I control emerald ash borers?

You can help control the Emerald Ash Borer by not moving firewood. You can also have your ash trees treated with insecticide by a tree care company.

If you think you have found emerald ash borer you should contact 311.

Please visit the City of Winnipeg's Parks webpage for the latest EAB information .

What are those large triangular green traps hanging in the ash tree?

EAB trap

The large triangular green traps you see hanging in ash trees in Winnipeg are pheromone traps that are being used to monitor for the presence of the emerald ash borer. The City of Winnipeg and Province of Manitoba are monitoring these traps in conjunction with the Canadian Food Inspection Agency. The traps contain a pheromone that attracts the beetle to the trap and these traps will be in place from approximately mid-June until the end of August. Please do not disturb these traps as they are an important tool for determining if the beetle is present in the City of Winnipeg. If you find one on the ground or have any questions regarding the traps, please contact 311.

Last update: March 2, 2022
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or 1-877-311-4WPG
Media inquiries: 204-986-6000

Administrative Office and Research Laboratory
1539 Waverley Street
Winnipeg MB R3T 4V7

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Winnipeg MB R2L 1V2
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