larch sawfly larva
Larch sawfly larva
Credit: USFS

You might blame climate change. Seasons with deep insulating snow that keep the iron cold from freezing the bugs overwintering in the duff. Or maybe it’s the dry, hot summers, when sawflies and beetles and leaf miners fatten on the trees.

Such shifting patterns supposedly triggered the spruce bark beetle epidemic, wiping out a couple million acres of white spruce across southern Alaska. Maps showing vast stands of brown snags on the Kenai Peninsula now serve as climate change icons.

This era of insect has spread like sunburn throughout urban Anchorage, where summers have warmed slightly over the past 50 years and nursery stock has seeded the town with invasive pests. The birch go brown by August with alien leaf mining larva that arrived without any natural predators (though federal entomologists have seeded a city park with a predatory wasp.) Woolly chewers crawl the alder. Aphids flitter like green dandruff. And my solitary Larch — a luminous green giant in mid-summer that glows like gold each fall — has been invested by little green worms.


Related to western larch of the Rocky Mountains and the eastern larch, called tamarack, of Alaska’s Interior, my Siberian larch came home with me from a one-guy nursery in the back of my old Isuzu Trooper in 1994. So small that its terminal bud hardly reached over the seat back.

I planted it in a sunny spot by the bike shed, and watered it regularly. At first, I had to support it with a fence post, the thing was so spindly and weak. When a moose bit off its top bud (and if you can explain that you get a Smokey badge), I tied up a lateral branch that soon took over. The thing shot for the sky.

The tree grew more than a foot per year, its foliage eventually spreading almost 20 feet in an incredible spurt. When my youngest son was a baby, my wife would picnic under its branches with the kid on a blanket. Two different Labradors snoozed in its shade on hot afternoons. It coats the lawn with needles and rumples the earth with its roots. It controls the solar budget in that corner of Anchorage with ruthless arboreal efficiency worthy of a rain forest.

And then came the bugs.

It was 1999. A clump of them had come off on my T-shirt, twisting like living green threads. I soon discovered larch sawfly larva on almost every branch — tiny bright green maggots that waved their blunt bodies in the air. Blind, mute, grotesque. I picked them off and flicked them away. But there always more, and they grew fat. No birds ate them. No predatory wasps laid eggs in their bodies. Black head, segmented bodies, they stripped the branches of the needles, one by one, their purpose clearly focused on destroying my tree. I thought they were unspeakably offensive, like boogers splattered on a work of art.

An entomologist explained over the phone: the larch sawfly had invaded the continent over decades, winging tree to tree until it reached Alaska’s interior. An outbreak had all-but wiped out thousands of acres of mature tamarack. And now, perhaps through an accidental transplant of ornamental larch from Fairbanks to Anchorage, it had been brought south of the Alaska Range and continued its assault. Try soap, he said.

So I bought a spray bottle of insecticidal soap — a slimy, slippery solution that fizzed over the larva in hissing whitish suds. The film coated their bodies to stop all respiration, causing them to writhe with what would have been agonizing suffocation in a mammal. Make no mistake, I wanted them off the tree and dead. But I hoped the reaction I observed was involuntary response to stimulus.

I’ve kept it up every summer since. The larva erupt; I spray. To save money, I started using dishwashing soap. I catch hundreds if not thousands of them before they have a chance to grow. Though I miss the ones high on the tree, most of the colonies seem closer to the ground, where the adult flies rise from the dirt.

By August of this past year, I sensed victory. The needles brushed out in deep green clumps, as thick and soft as fur. And then I found a single fat worm, alone on a branch, munching away on late-summer growth. It was almost hidden, so well matched was the color of its skin with the color of the needles.

I could not see any missing foliage. One bug alone on that branch had done no damage. I didn’t like seeing the thing, but I let it be. Even maggots got to eat.