3 Important Facts to Know About California Oak Worms

If your lush oak trees suddenly begin looking ragged and leafless, suspect the California oak worm (Phryganidia californica). This pest is a member of the same family as butterflies and moths and is also a native of California.

The Monterey Bay, Salinas Valley, and adjacent regions are prone to California oak worm infestations. Here are three more facts about California oak worms.

You may notice that leaves are being chewed to bits on your oak tree and wonder what the problem is. The problem — in the case of the California oak worm — can be observed in four basic stages near your oak trees.

Several dozen eggs are laid on the undersides of leaves. They appear white with red centers. The eggs may change to brown or pink-tinged when they're ready to hatch.

Called oak worms, the 1/10-inch long hatchlings are actually caterpillars that feed on oak leaves. The caterpillars have large, brownish heads and yellow-green bodies with dark stripes running the length of them. At maturity, the caterpillars reach close to an inch long and have distinctive black and yellow stripes.

In the chrysalis stage, the oak worm or oak moth can be found attached to tree trunks, leaf stems, leaves, and nearby walls. The pupae are white with segmented head sections accented by black markings. More distinctive black tiger stripes run the length of the chrysalis's lower sections.

The light brown or gray oak moth reaches around 3/4 inch to 1 inch in length, and its wings have distinctive dark brown veining. Male moths have hairy antennae, while female antennae are hairless.

The caterpillars overwinter on trees in warm, dry months and drop to the ground in May. In June, look for swarms of California oak moths laying their eggs in the afternoons.

When the California oak worms mature in May, they start falling from oak branches. People, cars, and patio furniture become inundated with the squishy, striped pests. Some of the caterpillars make their way indoors.

The dropping of the larvae is gross, but the caterpillars don't bite or sting. They simply want to find a place to climb up so they can become pupae and then morph into real flying moths. You may see the caterpillars wriggling up light poles, buildings, and fences to find a place to attach.

Although your trees may look like they've suffered a horrific accident or disease, most oak trees survive the occasional oak worm feeding frenzy. The outbreaks may occur in your area for a year or two, and then you won't see the California oak worms for several years.

You can give your oak trees the best chance at surviving a sudden oak worm outbreak by:

• Watering trees well, especially during droughts
• Feeding trees adequate nutrients
• Protecting roots and trunk
• Pruning diseased branches and overgrowth

If you have valuable ornamental oak trees, you may not want to suffer through an oak worm outbreak. You may also have sick or vulnerable trees that can't withstand an onslaught of ravenous caterpillars. Fortunately, your pest control company has solutions to keep the worms and moths at bay.

Spraying is one option to control the defoliation and moth swarms. Chemicals including microbes, botanicals, and insect-growth regulators should always be administered by professionals with the proper equipment.

Most years, you won't need to treat your oak trees for California oak worms. However, it's nice to know you have the option to have your trees sprayed when the oak worms are getting out of hand.

Contact Monterey Bay Pest Control Inc. to schedule California oak worm treatment for your oak trees. We care for trees in Monterey County and the surrounding area.