Deciduous trees are an important part of many landscapes; they serve as windbreakers and markers for property lines, and they also provide privacy, shade, and aesthetic value for your home. However, sometimes trees are planted in less than ideal locations or the conditions around existing trees are modified in a way that may put them at risk.

Trees that are under stress become more vulnerable to invasion by insects and pests. These invasions are often a symptom of underlying problems, such as poor soil aeration from overwatering. Identifying the problem early on and taking corrective action is crucial for improving the vigour of trees and preserving their integrity in the long run.

The first step to identifying disorders of broad-leaved trees is to determine whether the stress is biotic or living, or whether it is abiotic or non-living. Biotic stresses are the result of insects, mites, and disease such as bacteria or fungi, while abiotic stresses are the result of non-living factors such as the deficiency of water and nutrients, severe weather conditions, or the presence of chemicals such as salts or pesticides.

When looking for damage caused by insects, examine the affected tree carefully for signs of infestation. Many wood-boring insects create holes in the bark and sawdust during their tunnelling, while others such as the Gypsy moth leave behind empty cocoons. Other substances that can be left by insects include egg cases, honeydew, webbing, or feces.

Abiotic stresses can be more difficult to spot than biotic ones, but some strategies include checking the surrounding plants for similar issues, assessing the soil, checking the local weather conditions, and looking into any recent activity that might have occurred around the tree (such as construction or pesticide application).

It is important to remember that every year many trees are killed or damaged by human activity. Improper watering, improper maintenance, site alteration, construction stresses, and salt and pesticide damage are all significant threats to the health of trees in Ontario. Much of this harm can be avoided if we resolve to take greater care about the impact that our activities have on the environment, and for more information about identifying and removing threats to the trees around you please visit