City pitches $1.2M plan to save tree canopy from tiny pests

Thestarphoenix.com
Oct. 5, 2017
By Phil Tank

Saskatoon city hall is proposing a million-dollar plan to protect the city's beloved urban forest from European invaders about three millimetres long.

City of Saskatoon staff have been tracking the advance of a lice species native to Europe that targets black ash trees for more than two years. An assessment done this summer suggests 1,000 damaged trees should be removed, a city report says.

The report says the use of insecticides has only helped delay the need for trees to be removed and so a $1.2-million plan to remove and replant trees is recommended.

"Tree removal and replacement of affected trees in appropriate sites with another tree species is the most viable option to ensure the long-term health of Saskatoon's urban forest," the report says.

The tree lice, known as cottony ash psyllids, first appeared in Saskatoon in 2006, but virtually disappeared for unknown reasons in 2009. The species reappeared in the summer of 2015.

So far this year, 92 trees were removed and replaced in the Broadway, downtown and Riversdale business improvement districts with another 29 removed along 22nd Street.

The city tried injecting insecticides into susceptible trees in the spring, but it did not appear to slow down the trees' decline, the report says.

The city's urban forestry division is proposing the city spend $1.2 million over two years to replace affected trees. Funding for the $757,000 first year of the plan has been identified as coming from various reserve funds.

Funding sources for the second year of the plan of $423,000 have not yet been identified, the report says.

The City of Saskatoon's tree inventory number more than 105,000, about 27 per cent of which are ash species. Ash species were planted in Prairie cities in response to the threat posed by Dutch elm disease.

Now ash trees face the threat from psyllids as well as the emerald ash borer, which has not yet been found in Saskatoon.

Tree lice, which defoliate susceptible trees, devastated urban forests in Alberta cities. Calgary and Edmonton lost most of their susceptible trees and neither city plants black ash trees any longer, the report says.

Residents can identify the pest's presence by white cotton on ash leaves as well as leaves that have curled or turned brown or yellow. The tiny insects are light green or yellow green.