The deerweed on the hills at Leo Carrillo is being absolutely denuded by Western Tussock Moth larvae. Shrub after shrub along the trail has been stripped to bare stems, while others show a thick population of caterpillars munching away with abandon.

Orgyia vetusta is native to western North America, and is considered a pest by many because of the speed at which the caterpillars can defoliate a tree. They‘ve been reported on virtually all California oak species as well as various fruit and nut trees, ceanothus, hawthorn, manzanita, toyon, walnut, and willow. And deerweed!

The defoliation wrought by these caterpillars can trigger a chain reaction in ecosystems. Trees and plants serve as vital resources for numerous organisms, and their decline can throw food chains into disarray and diminish biodiversity. Tussock moth caterpillars have several natural predators, including birds, parasitic wasps and predatory beetles. Here’s hoping that the population reaches a healthy stasis at Leo Carrillo.