• Aaron Cull

How to Save Ailing Trees from Pests


Insects on Calgary trees is a natural phenomenon- no pun intended! Many insects are beneficial including lacewings, dragonflies, lady bird beetles, Ichneumonid wasps, Braconid and chalcid wasps. As long as your trees are healthy and there are enough of these valuable insects, they will limit the damage of many invasive pests.

Remember! A pest is only a problem if it reaches a threshold where damage is evident and is adversely affecting the health of the host tree.

Elm trees are susceptible to Elm scale. An overabundance of aphids is a sign of a stressed tree. Aphids are unique in that they can produce multiple generations of offspring in a single year leading to destruction. As they begin feeding, they excrete a honeydew substance that drips onto vehicles, patio furniture. To make matters worse this substance, high in sugar, promotes the development of another host, sooty mold. Visible symptoms include a black color on the trunk and branches. Since the health is compromised, Elm scale, another host can begin to forage on the branches and canopy. Their circular silvery nature is quite evident against the black backdrop of the aphid/sooty mold combination.


As a homeowner, the earlier this infestation is recognized, the sooner a less invasive treatment can be administered to save your elm tree. This is by far one of the most severe diseases in Calgary. We recommend spraying your tree with a pressure washer with a gentle spray around 10psi on the bark and branches of the upper canopy if possible. If the bark becomes damaged, the spray is too strong. Repeat spraying after a week if visible insects are present. If this is not enough to deter them and you see subsequent damage, reach out to our board-certified pesticide applicators. Remember this disease can be irreversible if left unchecked. Death can result in as little as 5 years.


The applicators at Evergreen Ltd. will first assess your trees for any harmful pests. An Integrated Pest Management (IPM) will be implemented to assess the damage of the pest in question and suggestions will be made to reduce the presence of the pest to an acceptable level. This will allow your tree to prosper in its environment, prevent any liabilities to your house or pedestrians and/or large fees to remove. It is important to use the least toxic option to treat the pest and when possible NOT to use chemical pesticides. Chemicals can be harmful to the beneficial insects that also inhabit your trees.


Often a few cultural changes in watering duration/frequency and supplementing with nutrients 2x a year (mulch, soil, organic fertilizer) can protect your greatest asset. Avoid synthetic lawn fertilizers or companies selling you a product unless they disclose what they are applying. Fertilizers often contain many salt additives which can leach from your grass into the roots of the tree and dessicate them in as little as a single season.


Contact Evergreen LTD for assistance with tree pests, infections, diseases, or any tree ailment. We can help save your trees and restore them to health.

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