Pesticide Application to Protect Native Plants and Animals in the Humber Arboretum

Starting on August 5, licensed staff from the City of Toronto's Urban Forestry department will be coming to control an invasive plant species in the Humber Arboretum with selective, targeted use of a pesticide. This work is vital in protecting the health and well-being of our local plants, animals, and ecosystems because the targeted species, dog-strangling vine, crowds out native vegetation and young trees and reduces the abundance of insects and other wildlife. Dog-strangling vine has a particularly negative impact on monarch butterflty populations, as the monarch butterfly mistakes the invasive plant for milkweed and lays eggs on plants which will not provide appropriate food for the monarch caterpillars.

The treatment area is marked with signs at every entry point around its edge. Information signage will be posted by city staff, along with the standard warning signage, to provide more information to Arboretum users. Warning signage is posted 24 hours before treatment, and is removed 48 hours following treatment, according to Ministry of the Environment and Climate Change guidelines.

Legislation: The Cosmetic Pesticide Ban, Regulation 63/09 under the Pesticides Act, allows some exceptions for non-cosmetic use of pesticides including a forestry exemption. The use of pesticides in forestry is essential to protect trees from competing vegetation in the maintenance or establishment of a forest. For more information about the Ontario Legislation call 416.325.4000 or visit

For more information about City of Toronto Forestry Management, please visit