In many parts of Canada, the ash tree is a familiar part of the landscape, but this much-loved species is under threat from a foreign invader. The emerald ash borer first arrived in Canada more than a decade ago, and this innocuous green beetle now threatens millions of trees. If you have ash trees on your property, learn more about the threat from the emerald ash borer, and find out what you may need to do to control the spread of this voracious pest.
The emerald ash borer's arrival in Canada
Experts first detected the emerald ash borer in Ontario in 2002, but within a few years, the insect had quickly spread to other parts of the country. In the next thirty years, Canadian authorities estimate that the beetle will cause $2 billion of damage, irreversibly changing the landscape. In parts of Ottawa, the ash tree represents 20 percent of the tree canopy, highlighting the opportunity the emerald ash borer has to feed and the devastation the insect could cause.
The emerald ash borer spreads alarmingly quickly, partly because the insect has hardly any natural enemies in the Canadian ecosystem. To make matters worse, the ash tree has little natural resistance to attack, so the beetles can quickly take hold. Studies show that the beetle can kill the tree one to four years after infestation. Within six years of infestation, the emerald ash borer can kill 99 percent of affected trees in a given area.
How the emerald ash borer damages trees
An adult emerald ash borer is about 14 millimetres long. The insect has a distinctive iridescent, metallic green back, with a bright emerald-coloured underside. The insect also has large, striking kidney-shaped eyes. That aside, it's not the adult insects that cause the problem. It is the larvae that damage ash trees.
Adult beetles lay eggs on the ash tree's bark, which then hatch into the larvae. These larvae, which can grow up to 3 centimetres long, cause damage by boring tunnels into the bark to feed. These tunnels cut through the layer of bark that transports vital water and nutrients around the tree. Without this life-saving layer, the tree will quickly die.
Signs to look for
You won't normally recognise a problem with the emerald ash borer until the insect has infested your tree. At this stage, the tree will start to show tell-tale signs of an attack. These signs include:
- Loss of colour in the tree's uppermost leaves, due to water and nutrient loss
- Thinning of the tree's crown as the branches start to die from the top of the tree down
- New leafy sprouts appearing from the roots or trunk as the tree tries to find new ways to get the nutrients it needs
- S-shaped tunnels under the bark
- D-shaped exit holes in the bark
You may also start to see increased woodpecker activity around the tree. This problem occurs because the larvae offer a tasty food source for these birds.
Dealing with infested trees
Research shows that insecticide treatment can stop an infestation, but only in trees where canopy thinning does not exceed 50 percent. It's worth saving your ash if you catch the infestation early. A mature ash tree can add value to your property, can help keep your house shady and cool and can even stop soil erosion.
Nonetheless, if the infestation problem is more severe, you will need to remove the tree. Without intervention, an infested tree will not recover. An infested tree also poses a risk to neighbouring trees, so it's important to act quickly.
It's easier (and normally cheaper) for a removal specialist to get rid of an infested ash while the tree is structurally sound. The cost of the work will vary from one property to the next, and the scale and cost of the work can vary. Factors that can complicate the work include:
- The size of tree
- Proximity of the tree to your home and other structures
- Proximity of power lines
- Location of the tree relative to roads or public access
Contact a tree removal specialist to get a quote for the work. He or she can also help you find out what you can do with the unwanted wood. Although you can use the felled tree for firewood, it's illegal to transport the wood elsewhere in the state. You can face financial penalties if you break quarantine laws in some states and cities.
The emerald ash borer presents a significant threat to Canada's native ash tree population. If you discover an infestation on your property, take prompt action to stop these hungry beetles spreading further.
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