More than one hundred black ash trees disappeared from downtown St. Albert this weekend after they were ravaged by tiny leaf-sucking bugs.
City crews cut down 119 black ash trees along St. Thomas Street, Perron Street and St. Michael Street on Sunday, including several large ones in the St. Albert Place parking lot. A tiny bug called the cottony psyllid had killed the trees. The trees along St. Anne Street were elm trees and were not affected by the bug.
The trees were declared dead last year, says operations supervisor Mike Jones, but were left standing for the Christmas light show.
"We're taking out, citywide, probably 400 to 500 trees this year," he says, most of which were black ash.
The cottony psyllid is a European bug that sucks sap from trees, according to entomologist Ken Fry of Olds College. They get their name from the cotton-like wax they extrude when young to protect themselves from rain and chemicals, and appear to target black and Manchurian ash trees. As adults, they look like squished aphids. The bugs were first spotted in Deer Ridge in 2000 and are thought to have arrived on an imported tree.
The bug weakens trees by sucking sap from their leaves, says city tree pest foreman Scott Stanley, causing them to shrivel. This in itself isn't fatal, but it makes the trees vulnerable to drought and other pests.
The city has not found an effective way to fight the bug, Stanley says. Insecticidal soaps can work against the psyllid, he says, but the city would need a huge amount of it to treat all its affected trees. Crews have used an injected pesticide on affected trees for the last five years, but it's had little effect: about 1,000 black ash trees have died in the last two years.
As a result, the city has decided to phase out its black ashes entirely. "We're admitting defeat," Stanley says.
Bye bye black ash
Contractors will be planting replacement trees from Spruce Grove's Kiwi Nurseries over the next few weeks, Stanley says. The replacement trees — Brandon elms and blazing autumn maples — cost about $150 each.
Staff will no longer be planting black ash in the city, Jones says, as they have no effective way to defend them against the psyllid. Cities around Edmonton are taking similar steps. "There are some trees in Erin Ridge that are still doing quite well," he adds, and those will be left standing.
St. Albert has about 1,296 black ash trees, according to the city's tree inventory. They have smooth white bark and oval-shaped leaves.
Anyone who spots a tree that could be infested with the cottony psyllid should call public works at 780-453-1557.
The psyllid should not be confused with the ash-cone roller, which curls rather than shrivels leaves. Cone-rollers are the golden worms that ride silk lines in the summer.
