Must-know advice for effectively treating your sick tree

November 27, 2014

If you have an ailing tree, chances are it's infected by one of four common tree diseases. Can it be saved? Here's some must-know advice for effectively treating your sick tree.
Powdery Mildew or white leaf disease

This type of fungus attacks the foliage of many species of trees. The leaves are covered by spots that resemble a white powder. The fungus first appears on the leaves in summer and stays until the leaves fall in autumn. The fungus usually has a minimal impact on the infected tree, but may stunt its growth—something to consider if the tree is young.

  • There's no specific treatment aside from raking up the affected leaves when they fall, ensuring proper ventilation of the plant and not watering it in the evening. It will also help reduce the chances of the disease spreading to any nearby trees.

Beech Bark Disease

This disease is caused by the beech scale: this insect drills holes into the bark, leaving the tree vulnerable to disease-causing fungi. It can be detected by the appearance of tree cankers and a white-coloured wax on the bark. A severe infestation causes a reddish-brown resin to leak from the tree.If you have an infected tree in your yard you can:

  • Spray the insects with very hot water (ensuring you don't scald yourself), scrub the bark with a stiff brush, or apply dormant oil (a home remedy made of vegetable oil and dish soap).

Dutch Elm Disease

This disease has killed countless elm trees and continues to wreak havoc, especially in eastern Canada. One of the symptoms causes leaves to wilt during the summer, turn brown, curl up and eventually fall off. Brown streaks will also be visible under the bark and on the inside of branches.

Dutch elm disease spreads very quickly and kills just as fast. Municipalities are undertaking large-scale programs to deal with it. If you have an infected tree:

  • Hire an arborist to evaluate the damage. If it can be saved, the arborist will trim off the infected branches, transplant varieties of resistant trees nearby and apply pesticide. Infected branches or tree stumps must be completely removed to prevent further spread of the disease.

White Pine Blister Rust

Tree rust is a fungal disease (mushroom) that attacks several plants. This particular strain preys specifically on white pines and is widespread across Canada. Its main symptoms are the appearance of a visible flow of resin from the bark, and the emergence of orange plates and cankerous lesions on the trunk which strangle it—as if it had a rope around it.

  • To treat tree rust, remove the cankers on the bark by hand or by cutting them off, while taking care to remove a little more than just the bark from around the affected area.

If you’re not sure what to do, consult an experienced arborist or other tree specialist to diagnose the problem and advise you on the best course of action. Your municipality or local garden centre should be able to provide you with names of recommended tree specialists.

Must-know advice for effectively treating your sick tree
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