A manager of an apartment building located in the residential neighbourhood of Saint-Basile-le-Grand, on the South Shore, requested our intervention after tenants on the ground floor reported an unusual coming and going of hornets along the front façade of the building. The building, consisting of six apartments on two floors, bordered an area of dense vegetation at the back. Initial inspection quickly revealed the presence of two separate nests: one in the crawl space under the ground floor balcony, the other under the eaves on the north side, in the almost permanent shade of the neighbouring tree.
Inspection and location of the two nests
In Saint-Basile-le-Grand, as in the residential areas of the Le Gardeur sector, apartment buildings from the eighties often had insulation under the balconies made with fiberglass materials that create accessible cavities. Our technician mapped the two nesting points and assessed the respective risks: the nest under the balcony was more exposed to residents, while the one under the eaves was larger, with an estimated activity of more than a hundred round trips per hour. Both nests had to be treated on the same day to prevent the survivors of one nest from joining the other and reconstituting a small but still dangerous colony.
Visual identification confirmed that they were indeed yellow-headed hornets, the most common species in Quebec, recognizable by their yellow markings on their heads and thorax. Unlike paper wasps whose nest remains open, the hornets’ nest is surrounded by a grey-beige envelope that protects the internal rays and makes direct access to the larvae impossible without prior treatment of the entrance. This distinction is essential in the choice of intervention method: a surface application would be ineffective, as workers outside the nest represent only a fraction of the total population. Only a treatment penetrating the envelope can reach the queen and larvae, guaranteeing the long-term elimination of the colony.
Simultaneous treatment of both foci
Our protocol for apartment buildings always calls for a coordinated response when multiple nests are present. Two technicians were deployed simultaneously: the first treated the nest under the balcony with an injection of residual insecticidal powder, while the second applied an expansive insecticidal foam in the eave cavity. The use of powder for the accessible nest and foam for the nest in closed spaces reflects our expertise in hornet extermination adapted to each type of configuration.
A forty-eight-hour waiting period was respected before the control visit. At this stage, no activity was observed around the two treatment points. Nests were removed and cavities were inspected for satellite nests or early hibernating queens. The manager was informed of each step in writing, in accordance with the rental management requirements.
Recommendations for the future management of the building
Following the intervention, we gave the manager a report detailing the points of vulnerability identified on the façade. Several caulking joints around windows and door sills had cracks that could allow future nesting of social insects. Caulking of entry points was strongly recommended before the start of the next cold season, when hornets are looking for protected areas to spend the winter.
For apartment buildings, pest management also involves raising awareness among tenants. We have provided an information sheet describing the behaviours to adopt in the presence of hornets: do not attempt to destroy a nest yourself, do not block the entrance to the nest (which causes a very aggressive defensive reaction), and immediately report any suspicious activity to the manager.
Comparable cases in residential buildings on the South Shore are documented in our portfolio, including this project dealing with a similar building and this file on wasps in rental settings. Our extermination company offers annual monitoring contracts specifically designed for building managers, with spring and summer visits to detect new colonies at an early stage, long before the situation gets out of hand. For an apartment building, the speed of detection and intervention is directly linked to tenant satisfaction and the reputation of the manager. A well-established pest management protocol is an integral part of responsible property management on the South Shore.