The Life and Destructive Habits of the Powder Post Beetle and Other Beetles

Address delivered by D. J. Cahill, President Western Hardwood Lumber Co., Los Angeles, before the Pacific Coast Hardwood Association at Del Monte

The growing menace of insect damage to wood in the tre-e,- in the 1og, in sawnlumber and in articles made from wood,.is receiviltg the eainest attention of entomologists in the forestry divisions of the departments of agriculture in our various states, our national government and our insular possessions.'

Not only are wood and tree life the objects of insect attack, but insect depredations extend also to vegetables, fruits, nuts, cereals, clothing, furs, leather, upholstery, carpets, books, papers, cured meats, live animals, and in fact almost everything that goes to provide us with sustenance and comforts. It is claimed that but for the constant war waged on in6ect pests not only vegetable, but animal life would be seriously threatened, and that man must. in order to maintain his supremacy, continue and intensify his efforts toward their extermination.

The species in which we, as hardwood dealers, are mostly interested because of the constant danger of their presence in our 'lumber stocks, are the Lyctus beetles, commonly known as the powder post beetles.

The United States Department of Agriculture, in Farmers Bulletin No.778, describes four species of the Lyctus beetles: Lyctus planicollis. which is found in the South Atlantic and Gulf states to A,rizona, Nevada and California, and is distinguished from the others because of its pitchy black color while the other three are rusty redbrown: Lyctus linearis, supposed to have been introduced into this country from Europe; the velvety Lyctus, known as Lyctus parallelopipedus, found in the middle and south central states; and the Western Lyctus, a native of California and known as Lyctus cavicollis. All however, are similar in appearance, ranging from onetwelfth to one-fifth inch in length, and are slender, flattened and elongate.

Other names given to specimens submitted to the Departments of Entomology of the University of California and Stanford University, are Lyctus striatus, Lyctus brunneus, and Lyctus impressus.

The attack of the beetle is extremely insidious and damage to infested lumber and panels is often so great €s to make them wholly useless for commercial purposes, before the presence of the pest is detected.

There are four periods in the life history of the beetle: the egg, the larva, the pupa and the adult beetle, The egg is deposited in the sapwood soon after the adult beetle emerges from the wood, being inserted into the pores of the wood by means of a long, slender flexible ovipositor. Within ten days the eggs are hatched, and in from six to ten days thereafter, the larva commences to burrow into the wood, proceeding in a general direction parallel with the grain. As the larva proceeds, it continues to grow until it reaches its full size, becoming a yellowish-white grub with three pairs of legs and with the tip of the body curved under toward the head. It then excavates a cell at the end of its burrow, and enters the pupa stage, from which it emerges later as a fully devetoped winged beetle.

The larva works in the sapwood exclusively, but when the adult beetle is readv to emerge, he will bore through either. the heart or sapwood. When this emergence takes place. the presence of the beetle is evidenced by little piles of pulverized wood fibre on the surfaces of the boards. The tarva at times al3o ejects this fine powder through a very small hole, but most of its work is under the surface and not visible. This makes it more difficult to detect the depredations of the pest until the harm is done.

These various species of powder post beetles, in emerging from the wood, leave a hole about one-sixteenth inch in diameter. which in itself does not indicate any considerable damage, but when the surfuce of the wood is removed, it will be found that the interior is a mass of pulverized wood fibre, packed into burrows through which the larvae have eaten their way, leaving only a thin outer shell, and walts between the burrows, holding the outer shell in place.

The active tife of the adult beetle ranges from February until September, during which time the adults come out and mate. Soon thereafter the female deposits her eggs, and the process com,menc€s all over again. Destruction proceeds from a time shortly aJter the egg is hatihed, until late in the season, when the larva reaches maturity. When the beetle has emerged, the damage is already done' although if the first generation has not completely destroyed the wood, subsequent generations will follow until the destruction ts comptete.

Control work is most effective in the winter months, when the insect is in the pupa stage, as destruction then eftectually disposts of him, while if -it -is attempted in the Spring or Summer after the adults have emerged, they will not be reached,. and will reinfest the wood as well as attack other wood.

In the case of articles of infested wood which have been varnished or painted. and the pores closed, thus preventing depositing of the eggs, the-female will re-enter a hole made upon emergence' and there deposit her eggs,

Only seasoned sapwood is attacked by the powder post beetle. because the chemical changes in the process of seasoning render the nutritive substance irl the wood, such as sugar and starch, especially suitable as food for the insect in the larval stage. Wood seasoned less than eight or ten months will not be attacked and the danger is greater as the seasoning continues.

It is therefore evident that new lumber arriving in the yard should never be piled on top of old'lumber because of the possible presence of beetles in the old stock and the danger of spreading to ihe new. Hickory, Ash and Oak are particularly liable to damage, although Walnut. Maple, Elm, Cherry, Locust, Poplar, Sycamore, Eucalyptus, Philippine Mahogany and other woods are subject to attack.

In addition to the Lvctus beetles however. there is another and very much larger beetli, Polycaon stouti. ciosely related to the powder post b-eetle, which works in a similar manner, but makes a much larger burrow, and upon emerging frgm the wood. leaves a hole about three-sixteenths inch in diameter. This beetle leaves his burrow packed with a filling nearly as hard as the surrounding wood, and moves through the wood in almost a straight line, parallel with the grain. His 6urrow is perfectly round. He emerges in the Spring and reinfests the wood.

Another large beetle is the banded ash borer, Neoclytus capraea' which attacks the log after the tree is felled. but will continue to work in the lumber after the log is sawn. This beetle is very destructive, but is not likely to reinfest the tumber. His burrow is flattened. which distinguishes his work from that of the large powder post beetle. He will attack Oak and Hickory also, and works both in sapwood and heartwood.

Many remedies are suggested for the control of these pests, but in the case of lumber, the practical and economical method is to subiect the material to treatment in a dry kiln under temperatures sufficient to destroy the beetles, the larvae and the eggs.

Extensive experiments made with Ash and Oak lumber by the Bureau of Entomology of the United States Department of Agriculture in the latter part of 1923 and, the early part of 1924, and described in a bulletin prep,ared by T. E. Snyder, Entomologist, and R. A. St. George, Assistant Entomologist, show that temperatures of 130 degrees F. and upr-ard, with a high humidity, maintained for l/z hours and longer, are fatal to powder post beetles. if all parts of the wood have at the beginning of the exposure to these temDeratures,. been brought to the minimum temperature of 130 degrees F. In a dry heat or low humidity, 180 degrees was found necessary to produce fatal results.

It will therefore be seen that in order to insure destruction of these pests, it is necessary that the wood be heated through and tbrough to a temperature of 130 degrees F. or over, and maintained at such temperature lor lft hours or more. Of course the time required to raise the temperature in all parts of the wood to a uniform degree varies according to the thickness. In inch lumber, it can be done comparatively. quickly, while in lumber two to four inches or thicker, it may require twenty-four to forty-eight hours or more; and manifestely, an adequate htrmidity must be maintained at all times in order to prevent damage by checking, case hardening or hollow-horning, and to insure destruction of the beetles at this temperature.

Kiln drying will not prevent infestation or reinfestation of lumber, and care should be taken that treated lumber is not placed in storage near lumber that may be infested.

The ground under lumber piles, and floors of bins, should be kept free from refuse. The insect will not live on the ground, and will die when taken from the wood. The use of hardwood sapwood pi.ling stickers should be avoided. Stocks should be kept moving, and the oldest disposed of first. Infested material, however, should not be delivered to a customer without his full knowledge of its condition, as the destruction will continue, even after the wood is used in a'piece of furniture, a cabinet, or as interior finiih, and should it be placed where strength is required, as in an automobile or truck hody, for instance, it may be the cause of an accident, resulting in serious property danage or personal injury. A furrier would be promptly condemned who knowingly sold a moth-infested fur coat.

New stocks should be watched carefully, and if evidence of infestation are present, the material should be immediately treated to prevent spreading of the pest to other stocks.

Steaming under pressure seems to produce such changes in the wood that it is no longer suitable for the powder post beetles. Tests conducted with Ash boards steamed 10 and 20 hours, respectively, at 28 pounds pressure and for 17 hours at 45 pounds pressure, rendered the wood immune from attack, but this me-thod is necessarity expensive and difficult because of the absence in lumber yards of adequate facilities, and it may also weaken or otherwise damage the wood.

Submergence of. sapwood hardwood in *'ater for a period of four months or longer changes the food value in the cells and makes the v/ood unsuitable for the operations of the beetle, but this also is impracticable.

Two coats of boiled linseed oil, or immersion in vats of hot linseed oil or hot creosote will also render the wood immune from attack, but if the larvae are already w'orking in the wood, the penetration may not be sufficient to destroy them. This treatment of course is not suitable for lumber to be used for finish, and can only be applied to woods used in construction, ll'here stain is not objectionable.

In addition to lumber, beetle infestation is found in a great variety of articles manufactured from Oak, Ash, and Hickory, prin- cipally, such as vehicle stock, implement handles, interior trim, flooring, furniture, cabinets, rustic work, etc.

In a B€ikeley home, buitt something over one year, and finished in quartered Oak, the maid complained of continuous trouble with dust on the panel projection, notwithstanding daily dustings. The Entomologist of the University of California was consulted, who found, upon examination, that the panels were infested with the powder post beetle.

In a Pasadena home, a room some 25'x40' panelled to the ceiting in Quartered Oak, shows extensive damage from beetle attack.

- A large quantity of antique furniture shipped fiom Europe- fqr a new California home was found, when insirected; to bc so daniagdd by powder post beetles, that many of the pieces collapsed, and had to be destroyed.

It is difficult to control this form of infestation, as fumigation cannot always reach the larvae in the wood, or penetrate througfr to the back sides of the panels, from which the beetles may €merge into the spaces between the,studs, where they mate and reinfeit the wood.

A rec€nt experiment in fumigation illustrates the difficulty in reaching the larvae in the burrows packed with powdered wood fibre. Samples of infested Ash and of Philippine Mahogany were treated in a 28" vacuum, with carbon bisulphide gas in the proportion of 40 lbs. liquid to 1000 cubic feet of air space, at a temperature uon 4u lDs. lrquld IWU cuDrc leet ot temperarure of 65 degrees F. After two hours, larvae of the powder post beetle in the Philippine Mahogany were found alive and active, and latvae of 65 of the landed ash borer in the Ash, although in a torpid condition, promptly revived upon being placed in a warm temperature.

Because of the difficulty of forcing fumigating gas into the packed burrows to feach the larvae. the treatment of infested plywood presents a serious problem. Fumigation will quickly kill the adult beetle, which has emerged, or is about to emerge, but the larva, which does the damage, is protected. in his burrbw, and not easily reached. Further experiments are now being made, and no doubt an effective treatment will be developed. It is not practicable to treat plyryood with heat, as e temperdture of 180 degrees F. which is necessary in a dry heat to destroy the eggs and the larvae, will crystalize the glue, and while 130 degrees temperature with a high humidity will effectively dispose of the beetles, this excessive moisture will loosen the veneers.

While the powder post beetles constitute, without question, the greatest danger to hardwood stocks, other destruqtive beel$s tare occasionally found. There is the Cedar borer (Hylotrupes ligneus) (Continued on Page 47)

TR 4293

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