The Attack of the Worms

One of the many effects of climate change is that winters in Montana aren't as long or cold as they used to be. This allows forest insect pests to have more hatches during the longer summer and lose fewer larvae in the winter. Their populations are expanding beyond the forest's ability to withstand assault.

In Idaho and BC, the large Ponderosa Pine forests have been devastated by Pine Bark Beetle. Here in Montana, we have lots of large monoculture Douglas Fir forests like the one I live in. They are being devastated by the Spruce Budworm. The name of this little monster is misleading, because their food of choice is not spruce, but fir. Douglas Fir is not even a true fir, but they don't care. They chow down on it anyway.
In the spring, the tiny black first-stage larvae make silk tents in all the shrubs and trees around. This year the tent stage went on clear into the middle of July.

The really destructive phase is the second larval stage. The little black worms morph into 3/4 inch long worms that are greenish with rust colored stripes and brown heads. These spin long fibers of silk and use them as parasails to float off through the forest. When they land on a tree, they inch their way to the ends of the branches and to the top leader and eat only the tender new growth. A year like this one, with a warm winter and then a long, wet spring and wet summer means lots of new growth on the trees which means lots of well-fed worms.

The trees around my house have been hit hard. The smallest trees, whose needles are all tender and new, are completely defoliated and killed. The larger trees have the very ends of every branch gnawed to a brown twig, but the older needles survive. The tops of some of the midsize trees are defoliated. It is heartbreaking to see the forest so sick.

The third phase is a pupa, or cuccoon. I don't know what their cuccoon looks like, but I am very familiar with the moth that emerges. It is gray with a pattern of slightly rust-colored patches. My house has been swarming with them all summer. When I had the walls torn open to build the bathroom, they got into the house in such numbers that one night I couldn't even see out a few of the windows for all the moth bodies swarming over them. Fortunately I managed to kill them and shovel them all up and dispose of them before my guests arrived. I thought my outbreak of moths was bad until I saw this picture of a budworm moth outbreak in Canada:

When winters were colder and longer, the numbers of budworms and moths were small enough for the population to be held in check by their main predator: birds. I have to say there have been a huge number of birds gobbling them up which has been very pleasant for the colors and songs they contribute. My favorite is a male Western Tanager that has been hanging around for weeks.
There is also a robin who has nested on the back porch and is so fat from all the moths and worms she can hardly fly. I hope these birds are happy with the smorgasbord. It is a heavy price the trees are paying for it.

I worry about how long our forest can withstand this assault. And I worry about the fire danger as the trees die. Not a very cheerful thought.