Killer worm invades Peninsula oak trees

MENLO PARk, Calif. (KGO) -- There's a killer worm that has Bay Area experts on high alert.

People are finding them on their cars, their homes and especially on their trees. It's an invasion of sorts on the Peninsula -- colorful caterpillars that can completely defoliate even a large oak.

They look harmless enough, pretty even to some people, but on the Peninsula the oakworm is on the attack.

David Nelson is an arborist with the Davey Tree Company. He says oakworms or the Tussock moth caterpillar can completely defoliate a live oak and it's especially problematic for one that's endured four years of drought.

"Pests will impact trees that are stressed," Nelson said. "It's a caterpillar basically in its larval stage that defoliates trees. They just come and just chew leaves, that's how they grow. And in their worst case scenario, they will defoliate a tree completely."

Janie Trimble has a number of old and beautiful oaks at her Piedmont home, trees that survived an oakworm infestation a number of years ago.

"It took the leaves off the trees. It caused them to look like they were dying. Fortunately, they managed to heal themselves without any kind of medication," Trimble said.

The first sign of an attack is cocoons, lots of them, nestled in a tree. Once the worms hatch, they climb up and begin to destroy the leaves.

"You have to contact a qualified arborist if it's in your tree. If it's on your structure, that would be a structural pest control operator," said Ron Eicher, a Davey Tree Arborist.

If not treated or destroyed, they will eventually turn into moths and fly away, but not before the damage is done.

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