One-fifth of ash trees the city is trying to save are dying anyway

The news has gone from bad to worse for the city's ash trees. Even many of the trees the city hopes save by injecting them with a pricey insecticide are dying.

And it's having trouble finding specimens that are healthy enough to be injected.

The city aims to inject 800 of Hamilton's most significant ash trees with TreeAzin. Among its targets: the iconic ash trees in Gore Park, and streets in Stoney Creek where all of canopy is ash.

But of the 207 trees injected so far, 19 per cent have died anyway. Crews have had to fell three large trees in Gore Park that the city tried to save, said Steve Barnhart, manager of forestry and horticulture. The injections simply didn't work.

Barnhart wasn't sure what to expect. But one in five trees dying despite the treatment is disheartening.

"It's a tough one," Barnhart said. "An insecticide, by its nature, should be effective."

I firmly believe at the end of the day, it doesn't matter what we do. We're going to lose all of the ash trees.- Coun. Maria Pearson

But many trees were already weakened by a 2013 ice storm, which could have led to more die back, he said. It's hard to tell.

Royal Botanical Gardens (RBG) has used TreeAzin to try to save 20 of its largest, more ecologically significant ash trees. And many of those have died too, said Lindsay Burtenshaw, RBG's terrestrial ecologist.

"I didn't expect to lose them," she said.

The ash borer problem dates back to 2002, when the invasive species was found in Windsor. Despite government efforts, it spread across Ontario and was found in Hamilton in 2009. Once the borer invades a tree, its death is swift and certain.

Searching for healthy trees

In 2012, the city approved a $26.2-million plan to remove all of its ash trees along streets and in public parks and cemeteries. That included the plan to save 800 of its most significant ash trees, with a $100,000 annual budget to do the required biennial update injections.

• Hamilton has lost 7,000 ash trees so far - and it's already painful
• City to identify 800 'high value' ash trees fit for insecticide treatment

The city has removed 6,761 trees and 3,747 stumps so far. Only 1,946 replacement trees have been planted, but staff plan to step that up in 2015 to total 3,777. The removal rate is about 2,300 trees per year.

As for the injections, Barnhart said the city wants to do about 600 more, but it's having trouble finding any left that are healthy enough to qualify.

Can any be saved?

In the next three weeks, city staff will take inventory to determine if there's been more loss. It's also in a hurry to identify new candidates — the injection window is June to August. 

The city is also looking at alternatives to TreeAzin. But at some point, Coun. Maria Pearson said, council will have to ask whether it's worth the tax dollars.

"That's the dilemma we're facing," said the Ward 10 councillor. "That's going to be the next issue we deal with."

"I firmly believe at the end of the day, it doesn't matter what we do. We're going to lose all of the ash trees."

The Hamilton Conservation Authority hasn't injected any trees, said Lesley McDonell, terrestrial ecologist. It has only monitored the trees and cut them when they started to die.