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ISA Certified Arborists
Serving North County Since 1983

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

Wood-Boring-Insects

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 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

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.

  • Goldspotted Oak Borer
  • Pacific Flatheaded Borer
  • Eucalyptus longhorned borer
  • Asian longhorned beetle

Aphids, Scale & Thrips

Aphids-Thrip

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.

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.

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 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

Mites

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.

  • Avocado brown mite
  • Brown mite
  • Citrus red mite
  • European red mite
  • Persea mite
  • Sixspotted mite
  • Six-spotted spider mite
  • Webspinning spider 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
  • Bulb mite
  • Pearleaf blister mite
  • Broad mite & cyclamen mite

Tree-boring Caterpillars

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.

  • American plum borer
  • Carpenterworm
  • 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