The City of Ottawa is testing a chemical insecticide more commonly used to kill grubs in its fight to curb the spread of the emerald ash borer.

The city's strategy has thus far been to inject a biological insecticide to try to save some trees, and fell those that are already dead.

But as the invasive pest bores into ash trees as far afield as Fitzroy and Richmond, councillor Maria McRae said she's keen to have another option to fight the pest.

"We've instructed the forester to do whatever he can to save these trees," said McRae.

Chemical not biologically based

A private company called Davey Tree has given the city some of a chemical called Confidor that it uses to try out on two dozen trees.

The active ingredient is used in a lawn chemical to control grubs and Davey is testing whether it will work on infested ash trees.

Forester David Barkley said the chemical is not biologically based like Tree-Azin, the insecticide that's already used around the city.

City to plant 2,700 new trees

But he said Health Canada has approved its use and the tree takes it up directly.

"It's an injection, so it's not a spray, or a folial application or a soil drenching like they've done in other areas," said Barkley.

McRae said the key to preserving the city's tree cover lies with planting a variety of trees to replace thousands of ash trees as they die off.

City workers will plant 2,700 new trees in the coming weeks, she said.