When it's below zero my nose hairs freeze - do invasive beetles freeze, too?
Posted by David Brooks | Tuesday, December 17, 2013
One of the reasons that we're seeing more invasive species hereabouts, from possums to ticks to black swallowwort, is that extreme winter conditions that can kill off those southerners are becoming less common due to climate change. (Climate models say, and so far the data agrees, that we will have more comparative warming in winter than in summer as we keep pumping out greenhouse gas to trap infrared energy.)
So when my front-door thermometer says six below, as it did this morning*, I inhale deeply, feeling my hose hairs freeze as a biological confirmation of temperature, then pump my fist in the air and cry: "Take that, you invaders!"
Alas, at least as far as tree-killing insects go, occasional wicked coldness won't slow them down much, according to research. Consider this depressing report from ISO Ontario:
Dave Roden, an entomologist with the Canadian Forest Service (CFS) at the Great Lakes Research Centre in Sault Ste. Marie, has been studying the “super cooling point” of the Asian long-horned beetle (ALB). That’s the point at which the last drop of water freezes in living tissue.
Roden believes the super cooling point for the ALB is –26 C (-15 F). As the weather turns cold, the insects undergo biochemical changes and produce glycol, or sugar, which prevents them from freezing unless they reach the super cooling point, “Just like the antifreeze you put in your car.”
But, he adds, some insects are “freeze-tolerant.” “They quite happily freeze. You can take the temperature down to where you want, and when the temperature comes back up, they come back to life.” Roden has exposed some beetles to temperatures as low as –40 C for 24 hours and seen them revive, mature and reproduce the next generation of insects.
So we were a good 10 degree to warm to really freeze Asian longhorned beetles. Ugh.
It's just as bad for emerald ash borer, as this research paper from USDA and folks in Minnesota says:
We found that larvae collected from naturally infested trees in Saint Paul, MN... had an average supercooling point of -25 C.
Again, we were 10 degrees too warm yesterday. It takes some real Northern New Hampshire cold snaps to slow down these invaders, and those cold snaps are getting ever rarer.
*It's an analog thermometer. Mhe back-door thermometer, which is digital, said zero degrees. Both are in roughly similar situations - located under a porch roof - so I assume the difference is technical, not micro-climate-related.