Field Key to Beetles in Pines

This key is designed to serve as a guide to identification of the more typical adult inner-bark and wood-boring beetles attacking Oklahoma pine trees. The key consists of two parts, one for adult insects and one for galleries made by the insects.

 

A ruler and a 10 to 15X hand lens will be very helpful in using this key. When possible, use both adult and gallery keys. If the insect does not key out properly  and proper identification is desired, place an adult in a small bottle containing 70% alcohol and mail to: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, Oklahoma 74078.  Please include information as to the type and amount of damage noted, host, date, and locality.

 

Some insects found in association with pines cannot be identified with this key. These would include larvae, flat bugs, predacious insects, and arthropods other than insects, such as mites and pseudoscorpions.

 

Survey Methods

Check your trees periodically for damage. Remove the bark and look for adult beetles and their galleries; look for “pin-holes” and large holes in the wood. Healthy, as well as damaged trees should be checked for pitch tubes and subsequent galleries. Beetle damage to pines can occur throughout the year with the heaviest damage occurring in the late summer and fall.

 

Descriptions of Larvae

 

Southern Pine Beetle (Dendroctonus frontalis)

This beetle is about 1/8-inch long. The posterior portions of the elytra are rounded as viewed from the top and side. A small notch may be seen on the front of the head with the 10X or 15X lens. The beetles have attacked pines of all sizes and can kill healthy trees. Pitch tubes may be found on the middle and lower trunk. This beetle makes “S” shaped galleries in the inner-bark of the tree.

 

Black Turpentine Beetle (Dendroctonus terebrans)

The adult is 1/4 to 1/3-inch long, dark brown or black. It is without a small notch on the front of the head; the abdomen is rounded. Pitch tubes are located on the lower trunks or stumps of pines with mechanical scars, or on trees occurring on poor drainage sites. The insect is more prevalent during dry periods. The pitch tubes are large, greater than 1/2 inch in diameter. The galleries are ovate or “D” shaped.

 

Ips Beetles (Several spp.)

Three Ips species frequently attack the crown and trunks of saplings and mature pines, which have been weakened by drought, fire, hail, insects, or other agents. Small pitch tubes        (1/4 inch or less in diameter) can be found on branches and/or on trunks. Even though each species has a preference for a portion of the tree, they may overlap. The brownish-red beetles make “H” or “Y” shaped galleries.

 

Ips avulsus, the smallest Ips beetle, is 1/8-inch long with 4 projections on the posterior of each elytron. With the invasion of this Ips beetle into the upper portion of the tree, other Ips species may invade.

 

Ips grandicollis is the medium-sized bark beetle, which is about 3/16-inch long and has 5 projections on the posterior of each elytron. This species commonly invades the middle and upper trunk.

 

Ips calligraphus is about 1/4-inch in length and has 6 projections on the posterior of each elytron. The beetle characteristically attacks the lower trunk.

 

Southern Pine Sawyer (Monochamus titillator)

The main distinguishing characteristics of this species are the size, color, and length of antennae. The gray-brown adult is 3/4 to 1 1/4-inches long. The antennae are longer than the body; they can be about 2 to 3 times the length of the body. The adult female cuts funnel-shaped pits in the bark surface and oviposits in the phloem. Larvae feeding beneath the bark at these points produce brownish frass and coarse-shredded wood. Circular pencil-size holes in the wood are signs that adults have emerged. The insect causes considerable degrading of lumber by tunneling through sapwood and heartwood of dead and dying pines or green logs.

 

Turpentine Borer (Buprestis apricans)

The adult is grayish-bronze with a metallic green cast. It is approximately 1 to 1 1/4-inches long. The antennae are shorter than the length of the thorax. Pines attacked may be fire-scarred or mechanically injured. Signs of this insect are elliptical emergence holes with tightly packed frass in the galleries. Generally these elliptical holes are found less than 6 feet from ground level.

 

Ambrosia Beetles (Xyleborus spp.)

There are several genera of ambrosia or timber beetles found in pines and their hardwood associates. The Platypus spp., as described in the key are about 1/4 inch in length with spine-like protuberances at the posterior of an elongate elytra. Adults attacking logs, lumber, and weakened trees can be recognized by fine white dust coming from pin-holes.” The gallery is described in the key. Other ambrosia beetles (Xyleborus spp.) look like Ips beetles but do not have the scooped-out, knobbed elytra.

 

Bostrichid Beetles 

These beetles are similar to the abrosia beetles (Xyleborus spp.) but can be distinguished by the base of the pronotum being distinctly narrower than the base of the elytra, while the abrosia beetle has the base of the pronotum about as wide as the base of the elytra. Refer to key to distinguish bostrichid from ambrosia beetles. Most generally one finds more bostrichids in hardwoods than in pines.

 

Infestation Prevention 

Ornamental pines provided with adequate food and water can reduce or overcome beetle infestations.

 

A stand of pines is best protected by practicing good management. Good management would include thinning old, unhealthy, and crowded trees; providing sanitation by preventing the build-up of large amounts of slash or beetle breeding habitats; avoiding mechanical damage to roots and trunks by logging and road building equipment; and prompt removal of felled logs and pulpwood. All trees that have been damaged by windstorm, lightning, fire, and/or machinery should be salvaged immediately or felled and sprayed with a registered insecticide. When the beetles attack, controlling their numbers becomes paramount.

 

Table 1.

A Field Key to Common Adult Inner-Bark and Wood-Boring Beetles in Pines in Oklahoma

 

Galleries

 

Control of Beetles

Control of the various bark and wood beetles varies, and identification of the insect becomes necessary. Trees under heavy attack generally have yellowish tops. If salvage is not possible, fell the trees and burn them; peel and burn the bark; or spray with a registered insecticide. With high value trees (naval stores, seed trees, etc.) one might consider spraying the trunks for a particular intruder.

 

Insecticide Safety Precautions

Safety precautions should always be followed. Use only the chemicals suggested for a specific use at proper dosages. Proper application equipment should be used. After spraying, clean equipment thoroughly.

 

The applicator should change clothing and wash exposed areas repeatedly with generous amounts of soap and water. This procedure should be especially emphasized if a chemical is accidentally spilled or sprayed on a person.

 

Chemicals should be stored in locked cabinets preferably out of reach of children and pets. Application equipment and accessories should be stored out of reach of small children to prevent accidents. Before using any chemical, READ THE LABEL to make certain that proper application procedures and safety precautions are being carried out.

 

Phillip G. Mulder
Professor of Entomology

 

Richard Grantham
Director, Plant Disease and Insect Diagnostics Laboratory

 

Don C. Arnold
Retired Survey Entomologist