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Advice for a diseased or declining tree

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Bacterial blight on an apple tree
Photo: Espace pour la vie/Pascale Maynard
Bacterial blight on an apple tree
  • Bacterial blight on an apple tree
  • Pine needle scale
  • Mechanical damage to a tree trunk
  • Damage caused by a woodpecker on a tree trunk

Why is my tree in bad condition?

Several factors can have an impact on the state of a tree’s health. For example:

  • environmental stress: drought, extreme heat, high winds, frost, ice, etc.;
  • growing conditions that don’t suit the tree’s needs: insufficient sun, compacted or poorly drained soil, lack of nutrients, improper soil pH, etc.;
  • incorrect cultivation practices: failure to respect the hardiness zone, planting too deep, inadequate watering and fertilization, poor pruning techniques, pesticide application, etc.;
  • mechanical damage: injuries or breaks caused by a lawnmower or edger, by major work (excavation, raising or lowering of the soil level, use of heavy equipment, etc.), by snow thrown by a snowblower, etc.;
  • diseases, pest infestations (insects, mites) or damage caused by mammals or birds.

What to do with a tree in poor health?

It’s not always easy to identify the cause(s) of a problem, to determine if intervening is necessary and, if that’s the case, to decide the type of intervention to perform.

If the tree seems to be ill, declining or dangerous, here’s some advice.

If the tree in poor condition is on a public right-of-way

If the tree is located on a public right-of-way, get in touch with your borough (dial 311) or your municipality. Municipal employees will do an inspection of the tree and carry out the required interventions.

It is forbidden to prune or fell a tree in the public domain.

If you own the tree

  • Take the time to examine it closely, evaluate its growing conditions and review your maintenance practices.
  • Consult the Green Pages for information on planting, pruning and fertilizing trees as well as on certain pests and diseases.
  • If needed, ask for advice from qualified nursery or garden center personnel, or contact an arboriculture specialist.
  • The Société internationale d’arboriculture - Québec (SIAQ) is a group of professionals dedicated to the care and preservation of trees. On the SIAQ website you’ll find a list of experts who can visit you to evaluate your tree and offer solutions. A lot of information about trees and arboriculture is also available on the site.
  • If a phytosanitary treatment, trimming or felling should prove to be necessary, check with your municipality or borough concerning regulations.

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