Calgary is urging vigilance from green thumbs in light of a tree-killing disease that appears to have spread its branches into the city.

Relatively new to the city, bronze leaf disease afflicts various species and hybrids of poplar, killing the infected tree within three to five years of infection. The disease is being diagnosed and treated in trees dotting city parks. Officials are warning homeowners to keep an eye on trees in their yards to prevent widespread infection, transmitted via airborne spores which disperse in early spring. Infection can be detected by the leaves, which become a dark-reddish, chocolate brown or bronze colour.