Crews finished up the last of the tree pruning activity in Okotoks last week, giving way to the annual elm pruning ban.
The ban is in place from April 1 to Sept. 30 of each year to prevent the spread of Dutch Elm Disease.
Tree pruning is done in the 'dormant season' to target certain harmful species and diseases, as bark beetles rest during the winter months, and cuts aren't likely to attract them.
The beetles spread the disease by carrying the Ophiostoma ulmi fungus from tree to tree.
"They're a bark beetle, and if they feed on a tree that's infected with Dutch elm disease, the fungal spores attach to its body. Then, when it flies to a new tree that's not infected, then those spores can get into the tree and cause it to die," explains Urban Forestry Parks Technician with the Town of Okotoks, Gordon White. "It's a devastating disease and difficult to manage. So, our prevention here in Alberta, that's kind of spearheaded by the Society to Prevent Dutch Elm Disease, has been working tirelessly to try and keep Dutch elm disease out of our province, and to date we're doing a good job, in my opinion."
Thanks largely to those efforts, Alberta has the largest Dutch elm disease-free American elm in the world.
Avoiding pruning elm trees during the ban plays just one part in preventing the spread, says White.
"Another huge prevention measure is do not transport firewood. This is one of the main factors that has caused invasive pests and diseases to take hold in regions where they're not normally. Wood is transported across borders, and then the insects emerge and, next thing you know, they're spreading a disease or the insect itself might be the agent that's causing the damage. It's really important that we burn firewood locally. If you're pruning elm, it's important to know that you need to dispose of it immediately and that's by burn or bury. So practically taking it to the landfill and getting it buried with the rest of the garbage is really the preferred method."
The Government of Alberta has more information on Dutch elk disease on its website.