Common Tree Insects & Pests in San Diego

Wood-boring beetles are the most common insects found in North County San Diego. Beetles that bore into tree branches, twigs and trunks include bark beetles, flatheaded borers, and longhorned borers. In addition to wood-boring insects, it is also common to find Aphids, Mealybugs, Psyllids, Scales, and Thrips.

▸Wood-boring beetles


Beetles that bore into tree branches, twigs and trunks include bark beetles, flatheaded borers, and longhorned borers. In each case, adults lay eggs on or in wood, and larvae feed within the wood, usually making distinctive tunnel patterns called galleries.

A number of different types of insects may bore into tree trunks and branches in their larval stages, producing sawdust or sap-filled holes and weakening trees. Most borers can successfully attack only trees that have been stressed by under- or over-irrigation, disease, lack of proper care, or injury by mechanical equipment. Usually, by the time the tree is infested with borers, there is little you can do to manage them other than improving tree vigor, prune out infected branches, or remove the tree. Insecticides are occasionally used to prevent infestations of bark beetles on high-value trees or to manage certain clearwing moths.

Bark Beetles

Bark beetles mine the inner bark (the phloem-cambial region) on twigs, branches, or trunks of trees and shrubs. This activity often starts a flow of tree sap in conifers, but sometimes even in hardwoods like elm and walnut. The sap flow (pitch tube) is accompanied by the sawdust-like frass created by the beetles. Frass accumulates in bark crevices or may drop and be visible on the ground or in spider webs. Small emergence holes in the bark are a good indication that bark beetles were present. Removal of the bark with the emergence holes often reveals dead and degraded inner bark and sometimes new adult beetles that have not yet emerged. Bark beetles frequently attack trees weakened by drought, disease, injuries, or other factors that may stress the tree. Bark beetles can contribute to the decline and eventual death of trees; however, only a few aggressive species are known to be the sole cause of tree mortality.

  • Western Pine Beetle
  • Cedar & Cypress Bark Beetle
  • Elm Bark Beetle
  • Engraver Beetle
  • Fir Engraver
  • Mountain Pine Beetle
  • Oak Ambrosia Beetle
  • Redhaired Pine Bark Beetle
  • Red Turpentine Beetle
  • Shothole Borer
  • Twig Beetle
Flatheaded & Roundheaded Borers

Adult roundheaded borers are medium to large, elongate, cylindrical beetles that are often brightly colored. They have long antennae, so are sometimes called longhorned borers or beetles. One common species, the poplar borer (Saperda calcarata) attacks aspen, cottonwood, poplar, and willow.

Holes in bark and stains or oozing liquid on limbs or trunks are common symptoms of damage by roundheaded borers. Foliage may discolor and wilt, limbs may die back, and branches or entire plants may be killed. However, roundheaded borers attack mostly damaged or dying plants; vigorous trees are rarely attacked.

▸Aphids, Scale & Thrips


These are all small, soft-bodied insects that feed by sucking plant sap. Damage may include leaf stippling, leaf bleaching, leaf curling and distortion, whitish waxy growth, or sticky honeydew (condensed sap) which may support the growth of sooty mold. Although most of these insects are related, thrips are classified in a different group.

Aphids, adelgids, and phylloxera
Adults of these tiny pests often lack wings. Aphids can produce copious amounts of sticky honeydew, which can lead to the growth of black sooty mold.
Hoppers, Sharpshooters, Spittlebugs
These insects feed by sucking plant juices and may leave drops of sticky excrement. Damage includes stippled, bleached or brownish leaves.
Mealybugs often have waxy filaments radiating from their bodies. They are wingless, move slowly, and congregate in groups covered with whitish mealy or cottony wax.
Psyllids & Whiteflies
Psyllids and whiteflies suck plant sap and excrete sticky honeydew. As adults, psyllids resemble miniature cicadas; whiteflies look like tiny flies with whitish wings.
Scales are immobile, wingless, and lack a separate head or other recognizable body parts, so many people don’t recognize them as insects.
Thrips are tiny, slender insects, with fringed wings and piercing mouthparts. They often leave tiny black dots of waste on leaves.



Mites are tiny and difficult to see without a magnifying glass. Mites in the groups listed below may damage fruit trees, vines, berries, vegetables, and ornamental plants. Spider mites cause stippling on leaves. Other pest mites cause a distorted growth of leaves, shoots, buds, or fruit. There are also many carnivorous species of mites that feed on other mites or small insects.

Spider Mites

Avocado brown mite

Brown mite

Citrus red mite

European red mite

Persea mite

Sixspotted mite

Six-spotted spider mite

Webspinning spider mites

Gall, bud, rust, and blister mites

Avocado brown mite

Brown mite

Bermudagrass mite (lawns)

Citrus bud mite

Citrus rust mite (silver mite)

Dryberry mite

Fuchsia gall mite

Gall and blister mites (ornamentals)

Gall and bud mites (flowers)

Grape erineum mite

Pear rust mite

Redberry mite

Tomato russet mite

Other Mites

Bulb mite

Pearleaf blister mite

Broad mite & cyclamen mite


▸Tree-boring Caterpillars


These caterpillars develop within wood, buds, crowns, or shoots of plants. They may cause a variety of damage symptoms including holes in trunks, weakened branches or crowns, and distorted shoot growth.

Tree Boring Caterpillars

American plum borer


Ceanothus stem gall moth

Peachtree borer

Pitch moths

Strawberry crown moth

Cypress bark moths

Juniper twig girdler

Monterey pine bud moth

Monterey pine bud moth

Raspberry crown borer

Contact Us
For more information about our pest & disease control services or questions on the health of your trees, please contact us directly at 760.745.7871.

We’re proud to offer reliable and quality tree services to North County San Diego residents, including the communities of San Marcos, Escondido, Fallbrook, Rancho Bernardo, Poway, Rancho Santa Fe, Del Mar, Solana Beach, Carlsbad, Encinitas, Oceanside, and Vista.