Mountain pine beetle mortality: it’s cold outside – but is it cold enough?

Photo_MPB_beetle_under_bark_sm2

Mountain pine beetles are vulnerable to the cold – but not as vulnerable as other insects, thanks to a special adaptation.

When it comes to winter weather, the equation is simple for most Albertans: the hotter, the better – and the past few weeks have certainly been hotter than most. Unfortunately, all good things must end, and in most parts of the province, our unseasonably warm weather has been replaced by the usual deep-freeze…at least for now.

But the cold (like many unpleasant things) has fringe benefits. Conditions are great for skiing, and there’s no longer a (long) line for the 7-11 Slurpee machine. And if you’ve lived in Alberta for long enough, you might have heard another one: cold weather, while bad for us, is even worse for the scourge of our forests: the mountain pine beetle.

Insects aren’t known for being able to thrive in sub-zero temperatures, so it might make sense that the colder it gets, the worse it will be on the beetle. But the truth is a little more complicated than that.

 The curious case of the antifreeze beetle

Most insects die in the cold because the water in their bodies freezes – but mountain pine beetles are cunning little critters. Rather than just waiting to be wiped out by sub-zero temperatures, they protect themselves from the cold by producing their own antifreeze – a chemical called glycerol – and stock-piling it in their bodies. The glycerol in their bodies helps keep the beetles from freezing.

The beetles start producing ‘anti-freeze’ in the late fall, and reach their full tolerance to the cold by January. Once this happens, they can still be killed by cold temperatures, but things have got to get really frosty – with sustained temperatures of -40 C or lower for at least two full days.

It’s much easier for cold weather to impact beetles when it happens in one of two specific ways:

1. When we get unseasonably cold weather early, before the beetles have had a chance to produce glycerol for the winter – in November, or even before that.

2. When there are extreme fluctuations in winter temperatures – we go from cold to unseasonably warm (like the past two weeks) back to below freezing. Once it gets warmer again, glycerol deposits start to break down and beetles start to lose their cold tolerance. When the mercury drops again, they’re more vulnerable to cold.

(It’s worth noting that this only applies to ambient temperatures – that is, how cold it is without taking wind chill into account. Unfortunately, wind chill doesn’t make the trees the beetles are in any colder.)

 So – what does this mean for Alberta’s fight with the mountain pine beetle?

We’re still working to better understand exactly how changes in temperature can affect mountain pine beetle survival. That’s why we’re supporting research by Dr. Kathy Bleiker over at the Canadian Forest Service’s Pacific Forestry Centre.

The goal of this research is to tell us more about how cold severity, duration, and fluctuation impact the mountain pine beetle, how it becomes cold-tolerant, and how it loses that tolerance. The research will use special environmental chambers to expose eggs, larvae, pupae, and adult beetles to different conditions. Hopefully, what we learn about the beetle through this research will allow us to better plan our next plan of attack.

Want more info about the mountain pine beetle, why it’s bad, and how we’re fighting infestations? Head to http://www.mpb.alberta.ca. And in the meantime, as we swing back into colder weather, just remember: if you’re hating it, mountain pine beetles are hating it more.

Understanding how beetles adapt to the cold helps us make sure our plan of attack is as proactive as possible. (Say that 10 times fast.)

Understanding how beetles adapt to the cold helps us make sure our plan of attack is as proactive as possible. (Say that 10 times fast.)

2 thoughts on “Mountain pine beetle mortality: it’s cold outside – but is it cold enough?

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  2. Pingback: Mountain pine beetle mortality: it’s cold outside – but is it cold enough? | lizfavot

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