The Western Tussock Moth infestation that created a nuisance in Flood Park in the spring 2026 has now largely abated. The caterpillars have gestated into moths and flown away, and the trees whose foliage they devoured are beginning to see regrowth. 

The moths have left behind pupation husks, which visitors may see clumped onto trees. Please avoid handling this material as it may cause skin irritation. 

Western Tussock Moth pupation husks — Do not handle, may cause skin irritation.

The egg masses laid by the moths throughout the park will remain dormant until next spring. San Mateo County Parks will take preventative measures to reduce impacts to the park the going forward.

For more information about this species see the University of California Pest Notes on the Western Tussock Moth.