Insect pests

Last updated June 12, 2024

The island of Montréal is home to species of insect pests that can be harmful to plants and property. Find out how to prevent or limit damage to your property.

Several species of insect pests have been reported in Montréal:

  • hackberry nipplegall psyllids
  • aphids
  • brown marmorated stink bugs
  • digger wasps (sand wasps)

Hackberry nipplegall psyllids

The hackberry nipplegall psyllid does not pose a threat to a tree’s survival, nor is it harmful to human health. Psyillids are primarily an aesthetic annoyance. However„ dense clouds of the insects can sometimes enter a home in September and October through a mesh window screen.

If you see these signs, you may have psyllids:

  • galls on hackberry leaves
  • clouds of minuscule insects around the hackberry tree

Simple actions can be taken to limit psyllids inside the home when adult insects are active in the spring and fall:

  • Avoid leaving outdoor lights on for no reason, as psyllids are attracted to light.
  • Close the blinds or window curtains during the evening to ensure that psyllids are not attracted to indoor light.
  • Keep the doors and windows closed whenever possible. If it is not possible to keep the windows closed, you might want to consider changing your window screens for grey-coloured screens with finer mesh (seven mesh openings per centimetre). P. celtidisvesicula psyllids can easily pass through standard window screens (five mesh openings per centimetre).
  • Caulk and seal the cracks around doors and windows.
  • If a few psyllids manage to enter your home in spite of your efforts, use a vacuum cleaner to capture them. After suctioning, close and discard the vacuum bag.

Our experts have developed integrated pest management projects aimed at reducing the use of pesticides. 

The technique retained consists of placing a blue plastic tarpaulin around the tree trunk and coating it with a special glue. This pest control strategy  aims to capture adult psyllids during their active period in the spring and the fall.


While aphids in general have a minimal impact on tree health, they can be harmful on occasion. In situations where there is a major infestation, aphids can hinder sap circulation, thereby weakening the tree and affecting its growth.

If you see these signs, you may have aphids:

  • the presence of honeydew on the underside of leaves and at the extremities of new shoots
  • ants travelling back and forth
  • Carefully inspect your newly-acquired plants to avoid introducing intruders into your garden.
  • Maintain plant strength through balanced fertilizing and by properly pruning and watering during dry periods.
  • Avoid drastic pruning and an excess of nitrogen fertilizer, which  promotes the rapid growth of tender shoots (suckers).
  • Incorporate a few trap plants into your flower beds to attract and capture aphids. Regularly destroy and replace the plants, and opt for sensitive species such as nasturtiums and petunias.
  • Regularly weed your garden, as weeds can provide shelter to aphids.

If you see aphids on a plant inside or near your home, we recommend the following actions:

  • Dislodge the aphids using a strong water spray, and repeat as required.
  • Trim and discard infested stems and leaves.
  • Manually crush the insects on the plant.

Natural enemies can be used to keep aphid populations down to an ideal level so as not to inconvenience residents.

Here are some recommendations to invite natural predators into your garden:

  • Make sure you have plants that flower throughout the summer.
  • Plant vegetation at the foot of trees to diversify the microhabitats used by these insects at different stages of their development (ex. shade, sunlight, roots, etc.).
  • Use indigenous plants in your landscaping, as they attract predators while being well adapted to our climate.
  • With the onset of winter, dry leaves should stay on the ground, as much as possible, to give them temporary shelter. This will incite natural enemies to stay.

Brown marmorated stink bugs

In collaboration with the national brown marmorated stink bug surveillance network, we are coordinating efforts to promote screening and identify this pest.

The brown marmorated stink bug causes significant damage to a variety of crops once it has infested an area. It can attack several hundred plant species, including the following:

  • fruit crops (apples, pears, cherries, lemons, apricots, raspberries and blackberries)
  • vegetable crops (kidney beans, tomatoes, sweet corn, peppers, etc.)
  • ornamental plants (maple trees, elms, lilacs, catalpas, etc.)

The brown marmorated stink bug has a maddening tendency to find its way into homes come the fall.

It is not capable of reproducing inside buildings, but can still secrete foul-smelling substances when disturbed.

This species poses no danger to human or animal health.

The brown marmorated stink bug (Halyomorpha halys) can easily be mistaken for other types of plant bugs, given its yellowish brown base coloration speckled with black spots.

Its distinguishing features are as follows:

  • The insect measures between 12 and 17 mm in length.
  • Its marbled brown body is shaped like a shield.
  • Its antennae and the sides of its abdomen have alternating pale and dark bands.
  • There are no teeth on the cheeks and edges of its thorax.

To prevent the brown marmorated stink bug from entering a building and to avoid a species invasion, we recommend that you seal off all potential points of entry:

  • Seal all cracks.
  • Repair or replace damaged window screens.
  • Before the onset of fall, remove or cover window-mounted air conditioners.

Indoors, brown marmorated stink bugs can be eradicated using a vacuum cleaner. It is important to empty or rapidly dispose of the vacuum bag so as to avoid unpleasant odours.

Digger wasps (sand wasps)

The digger wasp (also called the “sand wasp”) flies over the surface of the sand in playgrounds before dropping down and digging into the sand until it disappears.

The digger wasp does not represent a public nuisance, other than frightening people. The risk of being stung by a digger wasp is very low, as stinging humans is not in its nature.

Why digger wasps should not be eradicated

A single digger wasp can capture several hundred insects per year. They are our allies, as they:

  • help control insect pests, such as plant bugs, aphids and flies
  • contribute to the pollination of plants and flowers
  • occasionally attack the emerald ash borer

Help identifying an insect

Do you need help identifying an insect that has caused damage to your property? The Ask Our Experts service offered by Space for Life lets you do just that.

Extermination specialists

If you see insect pests or insects that pose a danger to human health on your property or inside your home, please call an extermination specialist that is accredited by a recognized association, such as the Association québécoise de gestion parasitaire

Have you seen insect pests in parks, daycare centres or other public areas? Find out how to report pests on public property.

Learn more about the topic