Die! Larvae, Die!


I know everybody is tired of people complaining about the cold- it is February, it’s supposed to be cold. So, I am going to turn it around, as I sit at my desk, gazing out the window at…hey, what is that squirrel eating? Avocado pit? Stupid squirrel, get out of the compost pile!

Where were we? Ah, yes, gazing out the window at the frosty back yard, I am both gleeful, and hopeful.

Gleeful, knowing that here on the flat it is -2 Fahrenheit, but up in the mountains, it is colder. Maybe cold enough in the woods to freeze the pine beetle larvae that are eating up our trees. Maybe it will be cold enough, long enough, to destroy a large percentage of the larvae, and we can get our woods back.

I say our woods, knowing that foresters and naturalists and others who take the long view see that pine trees falling to pine beetles doesn’t kill the forest, it just changes the forest. I’d like to be one of those people who take the long view, but I can’t. I love the woods, and I hate to see the trees go brown and topple over.

Pine beetles have always been here, but typically young trees can survive the attacks, and bitter cold kills many of the larvae, so there has been a balance in the past. Recently, winters haven’t been cold enough for long enough to kill them. So the forest changes.

Now the new larval threat is Emerald Ash Borer- they haven’t always been here- they came over from their native China around ten years ago, and are spreading. Native ash trees have no resistance. Signs of the insects have been found in Boulder County, (Boulder! Dang hippies!) and they are under quarantine. No products made from ash trees are supposed to leave the county, no mulch, no firewood, no nursery trees. Knowing that we are right next door, though, and that beetles don’t respect county lines, makes me wonder if they are soon to be discovered here in Larimer county.

They attack…well, not attack really. I mean the bugs are just living their lives, right, having sex, making babies, but it feels like an attack. So, the adult female ash borer lays her eggs in bark crevices of branches of ash trees. The larvae develop in the space between the bark and the wood, the cambium. The thin green layer of cambium is where sap flows, where water and nutrients flow out to the leaves from the soil. If enough larvae develop and destroy the cambium, that branch dies. If enough branches die, the tree dies.

The long view of the forester or the naturalist is hard here, too. Even harder, actually, because as much as I love the woods, I don’t live there. I have 2 big ash trees in my yard, and there are many more in my neighborhood. Losing these big old shade trees would will break my heart. Sigh. They will die eventually.

The city of Minneapolis has set up a system of proactively chopping down ash trees, and replacing them with different varieties of trees. Yep, chopping down trees that are fine, because in a few years they won’t be fine.

How does this connect to the weather? (Remember, 600 words ago I started out by saying I wouldn’t complain about the cold?) My hope is that the trees that are currently infected will be so cold during this cold snap that the overwintering larvae, curled up in their little serpentine tunnels under the bark, will freeze and die. Mwahahahahaha. Die, little larvae! Die!

For more info, and some alarming photos, check out http://www.americanforests.org/magazine/article/will-we-kiss-our-ash-goodbye/

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