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Oak Leaf Worms Are Defoliating My Oaks

California oakworm

“Attack of the Oakworms!” may never make it as a science fiction movie. But the concept is playing out in real life throughout the Central Coast.

Take a drive, and you’ll find that our early, spring-like temperatures are encouraging all sorts of deciduous trees to leaf out in fresh green.

Yet the coast live oaks (Quercus agrifolia) are behaving like it’s opposite day, losing their leaves and looking like brown skeletons looming over the landscape.

Get up close to any coast live oak that still has leaves, and you’ll see inch-long California oakworms (Phryganidia californica) munching through every last bit of foliage.

The voracious eaters devour the stiff, prickly leaves, methodically moving from one tree to the next.

The relentless march began in my coastal canyon neighborhood a couple of months ago. It has slowly proceeded up the canyon, only recently reaching our trees. The first sign was some browning at the tips. Now, amid a sprinkling of spring’s usual new leaves and pollen tassels, are brittle, twiggy branches, stripped of life.

And then there were two...

Apparently heaviest infestations can be tied to uncommonly warm, dry winters, which could explain our current outbreak.

Unfortunately, there’s not a whole lot we can do about the worms, other than to simply wait them out.

There’s no spray or treatment that will magically eliminate them. Instead, they’ll eventually morph into fluttery, dove-gray moths that can be annoying as well.

But despite the frustration of seeing our beautiful trees defoliated, the devastation will not last forever. The word from local arborists is that healthy oaks should rebound without serious harm.

Copyright, Joan S. Bolton. All rights reserved. Reproduction of text or photos in any form is prohibited without written permission.