Ontario homeowners may soon find their houses under siege by unwelcome guests — swarms of Asian lady beetles. Pest experts warn that as temperatures plunge this fall, the invasive insects will begin their annual migration indoors, and some areas could see a surge far beyond the usual trickle.
“These beetles respond to sharp drops in temperature,” explained Alice Sinia, an entomologist with Orkin Canada. “When that cold shock comes, they move quickly and in large numbers, all at once.” The Weather Network is forecasting a warm October followed by an abrupt transition to winter in November — conditions that could trigger a sudden, heavy migration.
Unlike native ladybugs, Asian lady beetles are larger, more aggressive, and range in colour from orange to yellow-tan, with an “M”-shaped marking behind their heads. They often congregate on the sunny sides of buildings before slipping inside through cracks, vents, or gaps in windows and doors. Once indoors, they can release a strong odour, leave stains on walls and windows, and even bite, causing irritation for some people.
Prevention is key, experts say. Homeowners should seal gaps around windows and doors, repair screens and weather stripping, and inspect exterior walls for cracks. Exterior spray treatments can also help reduce infestations. If the beetles do get inside, the best option is to vacuum them up — ideally with a bagged vacuum that can be sealed and disposed of outside. Crushing them indoors will only worsen the smell and staining.
While the beetles don’t cause structural damage, their presence can attract other pests like carpet beetles, which feed on the dead insects. Signs of an infestation include large clusters on walls, windows, or light fixtures, and piles of beetles collecting indoors.
Though they may resemble harmless ladybugs, Asian lady beetles are proving to be a far bigger nuisance. With fall colours nearing their peak and colder days ahead, Ontario households should prepare now for the possibility of a very buggy invasion.