Some tree diseases are caused by fungus or insects; others are due to poor care. What are themost common and destructive diseases that attack trees? How can they be treated?
Identifying the culprit
When the health of a tree is deteriorating, don’t immediately assume you’re facing an infestation of carpenter ants. Many culprits could be the cause.Two main reasons why illness in trees occurs are:
- Contamination by living organisms such as bacteria, viruses, fungi, insect infestations and destructive behaviour via larger animals.
- Environmental factors including frost, drought, poor drainage, moist conditions, lack of minerals and bad soil.
Insect infestations
With close inspection, you should see visible evidence including traces, furrows and sawdust. You may even witness a procession of pests on the tree's trunk, bark or branches.
You may also notice mounds of unknown substances on the underside of leaves, or you will see that leaves have been eaten away in several places. Discolouration of the leaves is also a sign, along with holes in the foliage.
- Common insects to look out for arecarpenter ants, termites, spruce budworms, span worms, birch borers, amber-marked birch leaf miner and emerald ash borer. They all hail from the forest and attack deciduous trees.
Mushrooms and bacteria
Fungi and bacteria grow well in hot and humid environments, like the soil. Therefore, when soil becomes contaminated the risk increases tenfold. They tend to settle in the fall and attack trees in the spring, as the temperature heats up.
- The emergence of brown, red or even black spots on a tree is usually the first indicator of fungal contamination. You’ll see these spots on the trunk, branches, roots or leaves.
- If mushrooms have already developed and are clearly visible, especially at the base of the tree, it means the tree has already begun to rot inside.
Other common diseases
- Twigs blight (larch, spruce, pine).
- Pitch canker (pine and fruit trees) attacks the branches and trunk.
- Annosus root rot (pine) attacks the roots.
- Dutch Elm Disease (the elm bark beetle carries fungi and bores into the tree) damages trunks and roots.
- Blister rust (spruce, fir, pine) attacks the needles and cones.
- Maple tar spot affects the foliage.
- Apple scabs (apples and pears) disfigures the leaves and fruit.
Prevention is better than a cure
With minimal effort, keeping these common enemies of trees at bay is easy. Here's how.
- Rake up all the leaves and branches that fall during the autumn and winter. You’ll alleviate excess moisture and reduce the risk of rot on the ground.
- Water your trees during dry spells.
- Apply the necessary fertilizer to trees in the spring, and again throughout the season to feed and strengthen them. They will be less vulnerable.
- Prune and cut away all broken or dead branches.
- Choose apple tree varieties that are resistant to apple scabs including Liberty, Dayton, Melrose, GoldRush and Wolf’s Paw.
