Regina, Saskatchewan has kicked off its yearly effort to guard city-owned trees from cankerworms, with spraying underway in targeted neighbourhoods since June 8, 2026. The annual program, run by the City’s Parks & Open Space Services, focuses on areas where insect counts are highest, aiming to prevent the leaf-eating larvae from weakening the urban forest.
“This program helps protect trees from cankerworms,” said Russell Eirich, Director of Parks & Open Space Services, in a City of Regina release. “We’re targeting areas where cankerworm numbers are highest so we can reduce damage and keep our trees in good shape.”
Crews are treating more than 4,000 trees this year, a slight dip from the 4,500 sprayed in 2025. The work is centred on parts of Cathedral, Heritage, Rosemont-Mount Royal, and Coronation Park, where monitoring with over 400 traps placed city-wide showed the greatest need.
The spray uses Foray 48B, a Health Canada-approved biological insecticide containing Bacillus thuringiensis subsp. kurstaki (BTK). The organic product kills cankerworms but is harmless to people, pets, and wildlife. It is applied when larvae are actively feeding, typically from mid-May to mid-June, though this year’s start came a bit later.
Residents in areas set for spraying get at least 48 hours’ notice through a hand-delivered flyer. The City recommends keeping family and pets indoors, shutting windows and doors, and moving cars off the street during the work. Only city-owned trees are treated; private trees are the owner’s responsibility.
Cankerworms, sometimes called inch worms, chew on fresh leaves of elm, Manitoba maple, and fruit trees. Repeated heavy defoliation can slow growth and even kill branches. The program relies on spring and fall trap counts to decide which spots need attention each year.
