City Efforts on Tussock Moth Caterpillar Hatchings

Each year, Tussock moth caterpillars hatch in the spring, often in late May. The recent rise in temperatures in 2026 appears to have brought the caterpillars out earlier than usual in Mountain View. Tussock moth caterpillars are native to this region. Although they are not poisonous, their hairs can cause skin irritation upon contact.

The City of Mountain View is actively implementing safe and effective methods to reduce Tussock moth caterpillar populations in our parks. Current efforts focus on cultural practices, including washing caterpillars off play structures with pressurized water and manually removing them through sweeping.

In areas with higher levels of infestation, the City will begin targeted insecticide treatments as time and weather conditions permit. The product being used is EverGreen Pyrethrum Concentrate, an organic, broad-spectrum botanical insecticide made from chrysanthemum flowers. It provides fast and effective control of Tussock moth caterpillars and breaks down quickly in sunlight.

The City's goal is to significantly reduce caterpillar populations while prioritizing environmental safety and minimizing impacts on beneficial insects.