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Managing Diseases and Hazards

​​​​​To maintain the health and longevity of your tree, it is important to be aware of the potential risks and threats posed to your tree by disease and injury.

As a private property owner, it is your responsibility to ensure that your tree does not pose a risk to the lives or property of others - you may be liable for injuries or damage caused by your tree if it falls down.

If you suspect your tree is a potential hazard, strongly consider having the tree removed as soon as possible. If you are unsure of your tree's condition, contact a certified arborist to conduct an inspection of the tree. Depending on its condition, an arborist may be able to save a portion of the tree and provide valuable advice about how to prevent further damage.


Hazard Trees

A hazard tree is any tree that poses a threat to people or property. Common hazards include:

  • Broken or hanging branches
  • Root problems that risk the stability of the tree
  • Rotten wood or other threats to the structural integrity of the tree
  • Cracks, splits or fissures in the wood

Hazard trees are often at risk of falling over and causing damage or injury. If you observe any of these conditions or believe your tree to be hazardous, consider having a portion or the entire tree removed. Consult a certified arborist if you are unsure.



Threats to trees from disease come primarily from fungal infections and pest infestations. 

Emerald Ash Borer

The most common and threatening pest in Ontario today is the Emerald Ash B​orer.

The Emerald Ash Borer is a non-native invasive species that attacks and kills ash trees. The insect is estimated to have infested and killed approximately 70 million ash trees in North America since it was first discovered. I​t is widely expected that it will eliminate virtually all ash trees in Southern Ontario.

The Township of King has developed an Emerald Ash Borer Mana​gement Strategy to identify and mitigate damage caused by the invasive pest. The Region of York, in partnership with other York Region municipalities, is committed to addressing this issue and ensuring the health and longevity of urban forests across York Region.

If you suspect that an ash tree on your property has been infested with Emerald Ash Borer, contact a certified arborist. They will be able to provide you with an assessment of the tree's condition as well as advice on tree protection, removal and replacement.


Asian Longhorned Beetle

A secondary infestation threat also exists from the Asian Longhorned Beetle

This non-native invasive species targets healthy deciduous trees such as maple, birch, elm, poplar, and willow. The insect was first identified by the Canadian Food Inspection Agency (CFIA) in the City of Vaughan in 2003. Since then, quarantine measures implemented by the CFIA have effectively contained the insect, resulting in the declared eradication of the pest by the CFIA. However, the City of Mississauga has reported an emergence of the insect in 2014, leading to new concerns about its presence in Southern Ontario.

While the insect is not known to be present in King, please notify the Township and CFIA immediately should you see one.

Other Pests

Caterpillars and other insects may create infestations and promote disease. If you notice large numbers of insects in and around your tree, you may have an infestation. A certified arborist will be able to provide an effective solution to infestation.


Fungal Infections

Fungal infections can occur when trees are damaged and the inner wood is exposed. While they are not always lethal to the tree, they may threaten their structural integrity over time and shorten their lifespan, in addition to damaging the aesthetic appearance and overall health of the tree.

Common signs of infection include spots and discolouration on leaves, sections of dead leaves or branches, and growths in and around the trunk.

What do I do if I suspect my neighbour's tree is hazardous?

1. Talk to your neighbour

They may not be aware of the condition of their tree and will address the issue themselves. Always give your neighbours the opportunity to resolve the matter first - this approach maintains neighbourly relations and supports a positive community atmosphere.

2. Consult a certified arborist or tree nursery

If you are unsure of the condition of your neighbour's tree and they are unable or unwilling to address the matter, speak with an arborist or local tree nursery to determine if what you see is a genuine hazard. They may be able to provide advice without inspecting the tree directly.

3. Contact the Township's By-law Enforcement Department

If your neighbor is unable or unwilling to address a serious hazard tree that is at risk of falling down, contact the Township's By-law Enforcement Department. Dead or dying trees and shrubs​ need to be removed under the Township's Clean Yards By-law​. Please note that this should be a last resort - in the interests of good neighbourhood relations, it is better to resolve the matter privately.​

A By-law Enforcement Officer will attend the property and request that the tree be inspected to determine its structural integrity and overall safety. If the tree is shown to be a hazard, the Township may order the property owner to remove the tree.​