Common Tree Diseases In Edmonton

Black Knot, Dutch Elm, & 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, western gall rust on pines and Dutch elm disease.  The most common pests are; satin moth, ash leaf cone roller, birch leafminers and spiny ash sawfly.

What are these pests and infestations?

Black knot disease

Black knot is a fungal disease that mostly affects cherry trees.  It causes brown to black swellings in the stems of cherry trees and is spread during periods of warm, wet weather.

How can it be treated?

  • Prune infected branches
  • Cut away diseased material at least ½ inch 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

Western Gall Rust

Pine gall rust is a fungal disease of pine trees that affects trees in the Edmonton Region.  It causes hip cankers, oblong growths or galls on the branches or trunk of the tree.

How can it be treated?

  • Prevent transmission by removing brush near susceptible trees.
  • Removal of badly infected trees. They should be burned to prevent further infection.
  • A fungicidal spray can slow the infection
  • Pruning, as always, can also slow the infection

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.

Satin Moth

The satin moth in caterpillar state that feeds off willow and poplar trees.  It can damage these types of trees as they eat the leaves during growing months.

How can it be treated?

  • Spraying insecticide was the old way of dealing with this pest. There are better ways now.
  • There is a small parasitic wasp that can suppress the moth population
  • Greenish eggs can be scraped off the bottom of infected trees in July to limit the population
  • Also, a sticky band can be put on your tree to limit the caterpillars from climbing it.

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 effective but is not the best way to treat 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?

  • Pesticides can be used to treat this pest but they are not considered the best form of treatment
  • A tiny wasp (Lathrolestes luteolator) selectivity attacks this pest and can control the population
  • Keep your birch trees healthy 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!