The emerald ash borer (EAB) is a highly destructive insect (originally from Asia) that feeds on ash trees, usually killing them within 2-3 years. The EAB was first discovered in the GTA around 2005 and has continued to devastate the ash tree population ever since. It is estimated that the City of Toronto will eventually lose almost all of its 860,000 ash trees (source: Landscape Ontario) and the outlook for York region is not much brighter.
The emerald ash borer’s worm-like larvae feed between the sapwood and bark along the entire length of the tree’s trunk, and on branches more than 2 cm in diameter. Larvae can be found under the bark during the summer months, although some can be found all year round. It is the feeding by the larvae (there can be hundreds even thousands of larvae in a single tree) that cuts off the flow of nutrients, which eventually kills the tree. The larvae leave an “S-shaped” or “zigzag” gallery of damage behind as they feed.
As the larva grows, it moults four times. At the end of the fourth moult, before becoming a pupa, the larva is J-shaped and has a slightly thicker and shorter body. This stage is called a pre-pupae and is first observed in September. An “exit” hole in the tree bark indicates when an adult has dug itself out to fly away and infest other trees.
Signs and symptoms are indicators of insect attack. A sign is physical damage to a tree, such as a gallery, a hole, or a feeding notch in the leaf, resulting from attack by the insect. A symptom is a tree’s response to insect attack and includes premature yellowing of foliage, dead branches, thinning crowns, or bark splits and cracks. It is important to be aware that similar signs and symptoms can be caused by other pests, drought, or cold stress and therefore you need an expert to verify that emerald ash borer is present in the tree.
New infestations of emerald ash borer are very difficult to detect. Usually by the time you detect these signs and symptoms, the tree is already heavily infested. However, if you identify these infested trees, there may be time to protect lightly infested trees in the area or slow the spread to other areas. This is why early detection is so important.
If you have an ash tree in your yard or on the city owned property in front of your home, you should learn about your options before taking any action. Visiting the website of your municipal and/or regional forestry departments will inform you of any programs that exist surrounding the control of EAB, and will indicate what measures are in place regarding trees planted on publicly owned land, including boulevard trees.
If your tree appears to be healthy…TREATMENT
While heavily-infested ash trees will ultimately succumb to the pest, healthy ash trees that are not yet infested or in the very early stages of infestation, can be treated. Currently TreeAzin, derived from the neem tree, is the only product registered for use in Canada against EAB. It is injected into the tree near the base and must be done by a licensed applicator. If your ash tree appears healthy, consider treatment with TreeAzin injections.
If your tree is infested…REMOVAL
If you decide to remove a tree on private property, you will have to incur the cost yourself. There may be removal permits required — check with your municipality. In many municipalities, infested trees that are located on the city-owned property in front of homes will be removed by municipal/regional forestry staff and replaced at no cost to homeowners.
REPLANTING. We encourage everyone who has space to plant new trees to replace those that have been or will be lost to EAB. Even if you haven’t personally lost a tree to EAB, planting new trees can help maintain the overall urban forest canopy.
– Ken Jorgenson