What’s Bugging You? Emerald Ash Borer (Agrilus planipennis)

In 2002, the Emerald Ash Borer (EAB) arrived in North America from N.E. Asia in wood packing and shipping pallets. This jewel beetle was first detected in the cities of Windsor and Detroit. Until 2017, they remained in the Eastern part of Canada and the U.S where they have continued to destroy millions of ash trees (Genus-Fraxinus). The Emerald Ash Borer will not affect the Mountain Ash family (Genus- Sorbus). By 2017, they had spread to Winnipeg; probably via transported firewood, and so far have not been detected in Saskatchewan.

So, you may ask, if it isn’t in Saskatchewan, why should we be worried? As gardeners, we should be proactive and familiarize ourselves with this insect as ¼ of all the urban trees in Saskatchewan are varieties of Ash (Fraxinus). If Emerald Ash Borer occurs in our province, it will be catastrophic and very costly to remove and replace affected trees.

Most 8.7 billion Ash trees in North America are vulnerable. The Emerald Ash Borer is difficult to detect as they are very small and can be in an ash tree for up to 5 years before the tree starts showing symptoms. Once a population of EAB increases in size, they will kill all ash trees within an area in 8-10 years.

In N.E. Asia, the Emerald Ash Borer attacks only weakened, diseased or stressed trees. In North America they prefer to bore into the wood of healthy young ash trees but will also kill mature ash as well.

The Emerald Ash Borer (EAB) is quite striking in appearance. It is a bright metallic green and 8.5-14 mm long x 3.1-3.4 mm wide. When they open their elytra and wings they expose a bright red upper abdomen. EAB can spread 3 – 20 km per year through flight and/or infested ash firewood.

Emerald Ash Borer Life Cycle

Adult borers emerge from an ash tree in May; fly to another ash tree, eat the leaves and mate. The females lay white eggs in the bark crevices of the trunk. The fertile eggs will turn reddish brown. After hatching, the larvae chew through the bark to the adjacent cambium layer where they feed and create long S-shaped serpentine galleries. The feeding galleries of the larvae stop the flow of nutrients and water, eventually girdling and killing the tree. As they feed they pass through four larval stages or instars. In the fall the fourth instar larvae bore chambers into the sapwood and outer bark where they fold into a ‘J’ shape. There they pupate and become adults the following spring. To leave the tree, the adults chew a D-shaped hole through the bark and fly on to the next healthy ash.


A female can live six weeks and lay 40-70 eggs. Some of the females may live longer and produce more eggs during that time.

Woodpeckers are natural enemies of the EAB and will strip off the bark of ashes to get to the larvae. Unfortunately, they find the adults not as tasty so we cannot rely on them to totally stop the spread.

Symptoms of EAB are as follows:

Leaf chlorosis, thinning and die-back of the tree crown, whole branches dying, S-shaped larval galleries slightly visible on the bark of the tree – pushing up from the cambium layer, suckering from the base of the tree, and D-shaped holes on the main trunk and larger branches.

The key to managing the EAB threat is education, prevention, early detection and removal of infested trees. Scientists at the Canadian Forest Services (CFS) in collaboration with the CFIA (Canadian Food Inspection Agency) and the U.S. Dept. of Agriculture have been working on this insect problem for many years. They have developed monitoring tools such as pheromone –based traps that detect the beetles’ presence early on in a season. They also inspect sample ash branches for the insect in areas known to have high concentrations of ash trees.

Biological control is also being implemented with the release of three parasitoid wasp species in affected areas. These wasps hunt other jewel beetles and EAB if present. The wasps will not totally wipe out the populations but do help identify the locations of this pest. The USDA is also trialing the application of an insect fungal pathogen that will attack the beetle internally.

They also created a botanical systemic insecticide called TreeAzin that has been used since 2008. This insecticide is made from the oil of the seeds of the Neem tree and is manufactured by BioForest Technologies Inc. It is injected into the ash trees and is commercially available to licensed pesticide applicators in Manitoba and Eastern Canada.

The spread of EAB is limited by winter temps of approx. -38 degrees C. They can survive down to -30 C because of antifreeze chemicals in their bodies. The larvae can also survive high heat up to plus 53 degrees C.

We can also do our part. It is illegal to transport ash firewood and wood products from an infested area into a non- infested area. If you are travelling to an infested area of Canada in your vehicle, it is also advisable to give your car a wash before heading home. These wiley little guys have also been known to hitchhike to new feeding grounds!


I always welcome any updated new information on any subject I write about in my blogs. Please feel free to leave comments regarding this topic below. Thank you!

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