The western tent caterpillar is a native insect to our forests. It population is cyclical. Over a period of two to three years, the population builds up and then crashes as natural parasites and diseases kill them off. Then we don’t see them again for maybe 8 – 10 years.
This week I saw some tent caterpillars in a recently planted site near Clatskanie (see photo). Last month, I saw lots more over by Sisters, where they were all over the bitterbrush around our family’s camping spot (“eew”, proclaimed my 9-year-old). Here on the westside, they prefer hardwoods such as alder, cottonwoods and willows.
While they may look alarming and can substantially defoliate the trees they infest, there’s little cause for alarm. The caterpillars are done feeding by late June, and the affected plants typically regrow a new set of leaves later in the summer. There’s no reason to spray insecticide – the best strategy is to wait it out and let nature take its course.
My guess is that we’ll see more western tent caterpillars in some localized areas next year.