Common Tree Diseases In Edmonton

alberta arborists

Common Tree Diseases In Edmonton

Black Knot, Fire Blight, & Other Common Tree Diseases In Edmonton

One of the most common questions Mike Burge of Arbor Man Tree Care gets asked is:  What tree diseases and infestations are most common to Edmonton?

The short answer is black knot disease, dothiorella wilt of elm, Fire Blight, & Bronze Leaf disease. The most common pests are aphids, borers, & leaf miners.

What are these pests and infestations?


Black knot disease

Black knot is a fungal disease that primarily affects chokeberry trees.  It causes brown to black swellings in the stems of cherry trees and is spread when the fungus spores in Spring.

How can it be treated?

  • Prune infected branches
  • Cutaway diseased material at least 6-8” below the knot
  • Sterilize pruning shears to prevent accidental spread of the disease
  • Burn infected prunings to prevent spreading after the material has been removed.

Dortiorella Elm Wilt

Dortiorella elm wilt is another fungal disease that causes wilting of elm trees.  It causes wilting or drooping of sapwood.  It is very difficult to distinguish from dutch elm disease.  The tree can fight the disease with proper care.   The disease can spread through spores and is hard to contain.

How can it be treated?

  • Keep tree’s stress level low. Watering during periods of drought can help lower tree stress
  • Pruning diseased limbs will help slow the infection
  • There are no anti-fungal treatments that have been shown to work on this disease

Dutch Elm Disease

Dutch Elm disease is a very serious disease that affects Elm trees.  It is also caused by a fungus and has destroyed millions of trees throughout North America.  Edmonton is one of the last places that has no Dutch elm disease.   It is transmitted by beetles which makes it very hard to contain.

How can it be treated?

  • Prevention is the most important part of treating this disease. It is illegal to prune elms from April 1 through September 30th.
  • Any elm branches that have been pruned must be disposed of or destroyed correctly
  • Elmwood cannot be kept as firewood and must be also destroyed if a tree is removed.

Ash Leaf Cone Roller

This is another caterpillar that feeds on the upper and lower leaf surfaces which causes them to look rolled.  They affect only ash trees and do not impact the health of the trees in a strongly negative way.

How can it be treated?

  • Spraying pesticides is not effective for this pest.
  • A tiny parasitic wasp can also suppress this type of caterpillar.
  • The damage is classified as cosmetic and is not serious.

Birch Leafminer

Birch leafminers are 3 species of sawflies that feed on the inner tissue of Birch tree leaves.  They cause the premature browning of birch trees in the Edmonton area.   This pest can cause the tree to be susceptible to other more serious problems.

How can it be treated?

  • Sytemic Tree Injections are the best way to treat the leaf miner.
  • Keep your birch trees healthy & well watered, and they can resist this pest.
  • Pruning deadwood, proper placement of birch trees, fertilizing them and water during drought will keep your trees resistant.

Spiny Ash Sawfly

The spiny ash sawfly is a small wasp whose larvae chew holes in leaves.  As they grow they will eat whole leaves.  The damage is primarily done to ash trees.

How can it be treated?

  • Pesticides are effective at treating this pest. Not recommended however
  • The damage from the sawfly is not significant enough typically to treat
  • Keeping your trees healthy will let them resist this pest
  • Pruning, fertilization, and water during drought will help your trees resist

There are many kinds of pests in the Edmonton region all with specific methods of treating them.  Make sure to call an expert at Arbor Man Tree Care to have your trees taken care of by a certified Arborist!

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