Information circling the Internet earlier this week suggested a silver lining to London’s record-breaking cold weather emergency — the death of the dreaded emerald ash borer.
As it turns out, people may have gotten their hopes up a little too early. According to Taylor Scarr, provincial forest entomologist with the Ministry of Natural Resources, the cold snap happened too late in the winter to be much of a help.
“There may be some impact of the cold weather on the survival of emerald ash borer in Ontario, but I think it will be minimal,” Scarr said. “It didn’t get cold enough, soon enough, fast enough. It has to happen early, it has to happen fast, and it has to happen deeply.”
Reports stemming from research out of Minnesota earlier this week said the extreme temperatures associated with the so-called Arctic Vortex might kill off a “significant percentage” of emerald ash borer larvae.
Scarr, however, said studies done in Ontario, including ones spearheaded by Brent Sinclair at Western University, found that once temperatures drop down to the -30C range, about half of the emerald ash borer larvae have a probability of dying. Put another way, it means still half of the insects will survive.
And that, Scarr said, was looking at the temperatures in January and February. If these cold temperatures would have occurred in November or December, it might have had more of an impact.
“There may be some minimal impact, but the point where half of them die is -30C, which is still colder than most of Ontario got,” said Scarr, adding that even with London’s record low of -26C, at this time of year, “there will still be pretty good survival.”
Julie Ryan, director of programs at Reforest London, said she was aware of the reports, a link to one article was even posted on the organization’s Facebook page.
Ryan understands both the temperature issues and the insulating factors of snow and tree back, but adds anything that helps reduce the insect’s population in London is a good thing.
“It probably just means a slowdown, it’s not like they are going to be wiped out,” Ryan said. “If the cold can slow the ash borer down, we say bring it on. Of course, we might be alone in that.”
The information quoted on the Internet, Scarr said, was related to the Minnesota study that was done between October and December. The insect is much more cold tolerant in January and February because it has had time to adjust.
The longer the emerald ash borer is exposed to the cold, the longer it has to build up natural anti-freeze in their system — something that is common for most insects over the winter.
“If we have quick a flash-freeze, drops from 0C to -25C in October, then a lot of them will die,” Scarr said. “If it happens in January or February, this time of year they are in their most cold-tolerant stage.”
Another mitigating factor is the temperature in the air isn’t the same as under the bark of a tree, which provides further protection. The insects under the thicker parts of the tree such as the trunk (as opposed to branches), will have increased cold tolerance. In addition, any snow packed around the tree will provide insulation as well.
Ironically, Scarr just happened to be in Annapolis, Maryland at a special meeting on invasive species where he sat in on a presentation on emerald ash borer. The presentation was being made by a colleague from Moscow, a northern city where the emerald ash borer does just fine.
“I knew about those news reports, so I asked him specifically about the cold temperatures we have seen and he said don’t count on it helping with your emerald ash borer problem,” Scarr said. “It survives and spreads quite well in the Moscow area and they have a lot colder temperatures than we do.”