STATE FOREST SERVICE.

LEAFLET No. 23.

A. D. McGAVOCK, Director of Forestry.

November, 19 34.

THE CONTROL AND PREVENTION OF BORER ATTACK IN BUILDINGS, ETC.

By ALEX R. ENTRICAN, Engineer in Forest Products, New Zealand State Forest Service.

SUMMARY. WHILE many buildings in the Dominion gre absolutely free of insect attack of all kinds, the prevalence of the common house-borer ~md the increasing ravages of the native two-toothed longhorn are such as to warrant the broadcasting of a few simple precautions which will reduce the incidence of attack, and of methods of treatment which will destroy the working insects. There is no short cut to success in exterminating -borers. Although the treatments recommended a.re easily applied, they call for painstaking care, and to be effective must be persevered with over a period of years. Constant watchfulness is likewise necessary to prevent new attacks and reinfestations. Firewood, fencing-timber, boxes, furniture, toys-in fact, all types of woodenware-are possible sources of infection, and every piece of wood introduced on to a property or into a building should be examined with the greatest care and the necessary control ·measures applied to prevent infestation of other timber. The following article recommends only treating materials which are readily available to the house-owner ~md usable without much risk. They include such common articles of commerce as turpentine, kerosene, creosote, &c., and simple methods for their application are detailed, together with sufficient information to enable the attacks by the more important boring insects to be identified and the appropriate control and preventive measures applied. In the case of serious infestations the employment of firms specializing in, the use of tJ.e methods advocated may well be justified. While complete success cannot always be achieved in arresting -insect attack and in preventing new infestations, in most cases constant watchfulness, coupled with appropriate treatment of the infested wood, will secure the desired results, and all fears as to the durability of the building and woodwork may be alla.yed. 2

THE IMPORTANT BORING-INSECTS AND THEIR HABITS. - The principal wood-...boring insects causing damage in New Zealand buildings and interior woodwork are:- (a) The common house-borer (Anobium piinctatum De Geer; syn. A. domesticum Linn.). (b) The powder-post beetles (Lyctus spp.). (~) Tft~l~~~ two-~~pt~~~~-J¥~9~o(n,c(-~~?go~~~~~~(~r~~t~s Fabr.). - How TO DISTINGUISH DAMAGE BY v ARIOUS INSECTS. The workings of these three insects are distinguished by the size and shape of the flight-holes made by the adult beetle in emerging from the wood after undergoing the usual life-cycle of egg, grub, and pupa and by the frass left in the borings. The -two former insects make a hole

from --,J2 in. to 1\ in. in diameter, that of the common house-borer being more truly circular in section than that of the powder-post beetles, which incline to make more oval holes, although the angle of emergence often conceals this difference. The two workings are better distinguished by the feel of the frass secured from the borings, that of the house-borer being quite loose and having a coarse, gritty feel as compared to the densely packed fine, flour-like powder left by the powder-post beetle. The longhorn workings are easily distinguished by the large, oval exit-holes measuring from l in. to i in. along the major axis. All timber showing borer-holes, however, is not necessarily undergoing active attack by insects. Many of those insects which live i_n the wood - of standing or in freshly felled and green timber ::>vre incapable of continuing their attack when the wood dries, so that in some cases the borer-holes discovered in woodwork have been made by insects which deserted the wood long before its conversion into sawn timber or before its use in buildings, &c. The pinhole borers (Platypus spp.) are usually responsible for this type of attack in New Zealand timbers, their bore-holes varying between i\ in. and 1\ in. in diameter. In most cases their borings are distinguishable from those of the house and powder-post beetles by their paucity, by the absence of frass, by blackening or darkening of the walls, by cigar-shaped streaks or stains in the surrounding wood, or by the fact that they usually extend across rather than along the grain, and do not range extensively through the wood. The attack is often of such a limited character, and the bore-holes so scattered and so well concealed in the figure of the wood, that it is not surprising to find a few in both joinery and furniture. They need occasion no alarm, since the insects which made them probably ceased their activities long before the timber was used, and are quite unable to live in the seasoned timber. In some industries, indeed, pinhole stock is commonly accepted and used for conce::>.led woodwork.

THE LIFE-CYCLE OF WooD-BORING INSECTS. The life-history of the three insects is completed in four distinct stages. The egg is laid by the adult female beetle. From this egg a minute grub or larva hatches out and commences to bore into the wood, so that its point of entry is so small and concealed as to be quite invisible to the naked eye'. The grub secures its sustenance from the wood through which it bores and enlarges its burrows as it grows. In all probability - 3 its power to assimilate the wood or some portion of it as food is due to the activities of protozoa and bacteria existing in its intestinal tract. In the case of both the -common house-borer and the powder-post beetle there is strong evidence in support of the view that reserve food, - either in the form of starch or sugar, is assimilated, because of the insects' preference for or confinement to sapwood and because heartwood contains isolated pockets of unused reserve plant food. The grub takes by far the greater part of its life-cycle to reach maturity, and it is during this stage that the insect does practically the whole of the damage to the timber. When it does reach maturity it bores its way close to the surface. of the wood and there forms a small cavity or pupal chamber in which it remains inactive for a comparatively short time as it changes into the adult beetle. ·· Finally the perfected beetle bores its way out of the wood, leaving its characteristic flight-hole so popularly and so incorrectly looked upon as its point of entry into the wood. The adult beetles have been known to bore through asbestos sheets, lead :flashings, &c.,· in emerging from the pupal chamber. They have a comparatively short life, usually of only a few weeks or less. Mating takes place soon after emergence from the wood, and as a result of their ability to fly considerable distances, the females are enabled to spread their attack to uninfested wood in the vicinity. Except for the common house-borer, which is attracted by bright sunlight, they shun the light aµd are most active at dusk and during the night. Death follows shortly after completion of the reproductive process. Some knowledge of the detailed life-habits of the three insects is essential to their intelligent control and the prevention of their attacks.

THE COMMON HOUSE-BORER. The life-cycle of the common house-borer varies from one to three years. The white, lemon-shaped eggs are laid in old flight holes as well as in cracks, crevices, and joints, and under splinters left by rough sawing. They are never laid on perfectly smooth surfaces. The larvre or grubs hatch out in a few weeks, and bore immediately into the timber, the shells of the eggs often serving to conceal their minute entry galleries. As the grub grows, the borings increase in size and range in every direction through the wood. The grub, which is whitish in colour, will attain a length of i in. if well developed. When it ultimately reaches maturity-almost at the end of the life-cycle-it bores towards the surface of the wood and forms a small, enlarged chamber in which it pupates or changes from the larva into the beetle. This pupal chamber may be less than 3\ in. below the surface or as much as i in., in which event a communicating tunnel is provided almost to the surface. The thin protective layer formed by the surface of the wood is sometimes pierced by a minute hole which serves to reveal the site of the pupal chamber ; and, after a short pupal period of less than a month, the adult beetle bores its way out at this point, emerging generally between December and March in Wellington, but somewhat earlier in the North and later in the South. The adult beetles vary from 1~ in. to i in. in length, but well-developed specimens usually measure about l in. The beetle is boat-shaped in form, red brown to dark brown in colour, and with its head withdrawn beneath a hood. They are reported to be most active at dusk and during the 4

night, although attracted in daylight to those portions of the building receiving direct sunlight. Generally they tend to inhabit old flight-holes by day and to lay therein large numbers of eggs. . Miller(l) reports the larvre to be parasitized by the grubs of a small, wasp-like insect, and that · a native species of Anobium is sometimes associated with the common house-borer. THE POWDER-POST BEETLES. These beetles commonly have a life-cycle of one year. Probably because the eggs are long, cylindrical, or worm-like bodies with a long strand at one end, they are laid only in the cylindrical cavities of exposed hardwood* pores, which are the large wood vessels characteristic of the timbers yielded by the broad-leaved trees. The eggs are therefore easily distinguished from the lemon-shaped eggs of the common house-borer, although requiring a very strong magnifying-glass to detect them. Never are they laid in cracks; crevices, &c., nor on smooth surfaces. They hatch out within a few weeks, the grubs boring immediately into the timber and tending to follow along the grain of the timber much more consistently than do the house-borers. The frass produced by their borings is exceedingly fine and tightly packed as compared with the gritty and loosely packed frass of the common house-borer. The larvre are whitish in colour and attain a length of ! in., reaching maturity in about ten months, when a pupal chamber is constructed close to the surface of the wood, the adult beetle finally emerging therefrom after a pupal period of a month at about the same time as the common house-borer. Although the beetles are somewhat shorter than the house-borer-from r:!o in. to -if in. in length-they are more elongated and are more flattened and brown to black in colour. All species of Lyctus beetles are distinguished from the A nobium punctatum by the fact that the head is visible from above, projecting beyond the thorax or hood. Either to obtain nourishment or facilitate egg- laying, the female cuts short incisions across the surface of the wood. These incisions have the effect of exposing further pores, into which it may insert its ovipositor and lay eggs. Unlike the common house-borer, they seldom fly during the day, shunning the light and collecting on the dark undersides of infested timber. They mate soon after emergence, but have a longer life by several weeks than the Anobinm.

THE Two-TOOTHED LONGHORN. Comparatively little is known of the length of the life"'"cycle of this insect, although it is suspected of being at least three years if not consider­ ably more. The eggs are deposited in cracks, crevices, and joints, under slight projections, or upon the surface of the wood.t The larvre, which are

* " Hardwood " is the commercial term used to distinguish the of the broad­ leaved trees, such as the native and the , &c., from those of the needle or scale-leaved trees, such as the true and totara, rimu, &c., known in contra­ distinction as" softwoods." (NOTE.-For botanical names of species see Appendix at end of report.) t Until recently it was believed that the female beetle drilled holes in the surface of the wood with its ovipositor preparatory to laying its eggs, but observations by A. F. Clark, Forest Entomologist, New Zealand State Forest Service, show that the ovipositor cannot be so used. 5 whitish in colour with a blackish head, bore along the grain and pack their tunnels with undigested wood dust, well-developed specimens attaining a length of I in. They make faint markings running around the walls of the tunnels while gnawing their way through the wood. In emerging from their pupal chambers, the beetles leave characteristically oval-shaped holes with a major axis of from l in. to ! in. They emerge several months later than the other two insects, the maximum emergence months throughout the country being April, May, and June. They are from -! in. to I in. in length, narrow-bodied, and chocolate to reddish-brown in colour.

OTHER INSECTS. There are, of course, a number of other wood-boring insects more or less common throughout the Dominion, and the State Forest Service would appreciate receiving specimens for identification and study. When sub,.. mitting these to the Director of Forestry, State Forest Service, Wellington, N. 1, inquirers should, if possible, include a fair-sized piece of the infested wood, together with full details as to its position in the building, &c. Detailed descriptions of most of the more important insects can b~ found in State Forest Service Bulletin No. 2, entitled "Forest iwd Timber Insects in New ZeeJand," by David Miller, available on application at 4s. per copy.

NATURE OF ATTACK AND TIMBERS INFESTED. Common House-borer. As judged by the prevalence of its attack, the common house-borer is the most destructive of all insects working in buildings and seasoned-timber products. In buildings its activities may range throughout the entire construction from sub-floor timbers and weatherboarding to roof-rafters and interior finish and built-in furniture, but seldom is the intensity of attack sufficient to effect materially the structural stability of the building, the insects sometimes being curiously selective in their atta.ck, infesting only one or two boards in a room, and ultimately, either from lack of sustenance or for some obscure reason, totally abandoning their attack. Furniture, musical instruments, clock cases, toys, boxes, and all kinds of woodenware are liable to attack, which is more general than in the case of buildings, and. often may be so intensive 2'S to m11ke the woodwork quite unfit for further use. Plywood appears particularly susceptible. The common house-borer favours old, well-seasoned wood, and seldom attacks freshly seasoned timber. For the initial attack sapwood also appears essential, but after it has been riddled and this food-supply exhausted, the insect may extend its ravages to the· heartwood. In this event, however, the attack is less intensive 2,nd more selective or localized, the intensity, generally speaking, decreasing towards the pith. Attack is seldom, if ever, found in the central figured and rosiny portions of the heart. If conditions are favourable to the existence of the common house-borer, extremely few, if any, species of timber, either native or foreign, are proof against its depredations. Kauri, totara, silver-, and kawaka are the most resistant of the native soft­ woods, even their sapwood being only occasionally attacked, their heartwood very rarely. White-pine is the least resistant of all, although its yellow heart is seldom, if ever, attacked. The remaining commercial softwoods, such as rimu, miro, and matai, &c., are intermediate in their resistance. 6

While the outer whitish sapwood of these species may be heavily infested under favourable conditions for attack, the true heartwood surrounding the figured heart is much more resistant and only sparsely attacked. Of the foreign softwoods, Californian redwood and Western red-cedar are probably the most resistant, although sapwood of the former is susceptible, as evidenced by attacks of both imported and locally grown wood. Imported Douglas and Queensland kauri and hoop-pine have also been attacked, as well as the sapwood of practically all locally grown exotic pines and , including insignis pine, Corsican pine, Digger pine, Torrey's pine, Jeffrey pine, Coulter' s pine, maritime pine, pitch pine, Scots pine, Western Himalayan , and Norway spruce. Probably the sapwood of all pines, .spruces, , and is liable to attack. The native beeches are probably the ;most resistant of the indigenous hardwoods, and tawa, taraire, kohekohe, and rewarewa the least resistant, although it is essentially the sapwood which becomes heavily infested. Broadleaf, hinau, and pukatea are also a.ttacked.

Powder-post Borers. Although not nearly as prevalent as the common house-borer, the powder­ post insects cause considerable damage. All classes of material may be attacked, from building-timbers, such as panelling and flooring, &c., to general woodenware, such as furniture and shovel-handles, &c. Numerous instances have occurred where the latter have been shipped from abroad without any superficial sign of attack, only to arrive in New Zealand with freshly made exit holes, indicating that the timber from which they had been manufactured had been infested long before shipment. Generally speaking, furniture and hi:mdles, &c., are more often attacked than building­ timbers. In contrast to the common house-borer, the powder-post beetles prefer freshly seasoned wood, and attack is possible within a short time of sawing and immediately a surface skin of dry wood forms on the timber. As soon as the sapwood ceases to yield sustenance, they abandon the timber and the attack ceases. Although the larvre work only in sapwood, the adult beetles, in seeking an exit from the pupal chamber, may bore through heartwood, &c., as in the case of the common house-borer. The powder-post beetles confine their attacks to the sapwood of various hardwoods. To lay their eggs the insects must insert ~heir ovipositors into the pores or wood vessels, which are seen on the end section of , for instance, as small holes and on the surface of boards as longitudinal cavities. It follows that wood with pores which tend to be smaller than the tip of the ovipositor are not as susceptible to attack as those with larger pores, a theory which has been conclusively proved by· the British Forest Products Research Laboratory at Princes Risborough. Thus, and sycamore are not as commonly attacked as oak and ash, although only very small-pored woods such as horse- are virtually proof against attack. Amongst other foreign hardwoods attacked are sweet chestnut, rosewood, walnut, and mahogany. Of the native hardwoods attacked, tawa appears to be the most susceptible. The beeches appear immune. On the other hand, a considera1He number of Australian hardwoods are attacked, Roughley and Welch(2) listing over seventy, including such well-known species as spotted gum, Tasmanian stringybark, grey gum, and grey ironbark. 7

The Two-toothed Longhorn. Unlike the other two insects, which .are foreign introductions, the two­ toothed longhorn is a native species. Known originally for their attack of dead forest-trees, the insects have gained prominence during the post­ war period by the extremely destructive nature of their attack upon a number of buildings constructed of the most durable timbers, including tota.ra, matai, and kauri. Numerous infestations have been reported from new dwellings within three to five years of erection, although buildings of all ages and types are being attacked. Furniture is rarely, if ever, infested. As regards the severity of its attack upon individual pieces of timber, the two-toothed longhorn is quite easily the most destructive of all insects attacking wooden buildings in New Zealand. ·It rivals the white ants of tropical countries and eats away almost completely the interior of the timbers both large and small, leaving such a thin, paper-like shell that, in the case of :flooring, it crumples and collapses in use. Although apparently it prefers sapwood and often confines its activities to that portion of the timber during the initial stage of its attack, once this food-supply has been exhausted it appears to work with equal facility in the heart-wood. For this reason the attack in its initial stages may appear quite localized or selective, with only a board, &c., here and there in the building infested. Ultimately, however, the attack may spread from board to joist, to framing, &c., until the structural stability of a complete section of the building is endangered, and several instances have occurred where it has been necessary to renew large portions of the flooring construction. For some reason it may completely desert a building after seriously damaging only a small localized section of the structure. · The insect merits special attention because its ravages may be well advanced before any signs of attack are visible. Seemingly not only have the larvoo a comparatively long life of several years in which to carry on their destructive borings before they emerge as beetles, but these latter shun bright light, and prefer to emerge on the concealed surfaces of the wood, such as the underside of floors, &c., where the flight-holes ordinarily go unnoticed. When eventually flight-holes do appear in exposed wood­ work, the borings are found to extend considerably beyond the points of emergence, and the damage is probably at an advanced stage. Amongst the timbers attacked are kauri, matai, rimu, miro, totara, and macrocarpa. Flooring appears more generally attacked than any other class of ·product.

DETECTION OF BORER ATTACK. The first line of defence against borer-attack is to make a thorough survey of every piece of timber on a property, whether this be in the form of firewood, boxes, forniture, or in the building itself. All timber showing flight-holes should be regarded with suspicion and subjected to the minutest scrutiny. Are insects still working in it or not? That is the practical question. .'.J;Ji:e-~e.th.rultLQf~is.~~g~i..S,hing.-between--the- work of the pinhole r"bol'ers,-whieh-cannotlive in·converted timber; and that of the insects under · .diaCllsgjcH1-h.a-w~already. been reviewed. In the _interior of buildings and in furniture, &c., signs of active attack are readily available from the new appearance of the last year's flight-holes, the insides of ·which appear quite fresh and ·light coloured, but in exterior timbers these weather rapidly and additional evidence must often be looked for. Any discharge of powdered 8

wood from exit-holes should be regarded as prima facie evidence of attack, and the timber earmarked for treatment. This discharge may take ·place at practicalJy any time of the year owing to newly created frass being forced out through old exit-holes, but is most noticeable at the time the insects are approaching the surface to form their pupal chambers, and inspections should always he made at the appropriate periods of the year. Even where no exit-holes have yet appeared, a discharge of frass may take place at joints or cracks in the timber as the larvre pass these points in their borings. In the case of the powder-post borers, a minute discharge is possible also through the pores of the hardwoods infested. Literally, every piece of timber which can be examined in the building should be carefully inspected for these signs of attack. Both sub-floor and roof timbers should be inspected wherever possible, the· former in particular for signs of attack by the two­ toothed longhorn. It is not sufficient, however, to make only one such inspection, treat the affected woodwork, and imagine that the problem is solved. Two inspections should be made regularly each year in the early spring and the late summer and autumn, and the appropriate measures applied on each occasion. Furthermore, each piece of wood brought on to the property at any time, whether in the form of firewood, boxes, timber, or furniture, &c., ~hould be carefully inspected and, where necessary, treated. Failure to observe these precautions may result ultimately in attack or reinfestation. The importance of making regular inspections in the case of newly erected buildings cannot be overstressed, as the early detection of attack will facilitate treatm~mt and simplify subsequent preventive measures. It must not be thought that, because the timber has been sterilized by kiln-drying, it is immune from further attack. This is not so. It may be attacked like ordinary air-dried timber. Needless to say, the greatest care should be exercised in the erection of new buildings, and the employment of an architect who will carefully examine all timber is invariably to be recom­ mended. Where the timber has only just become infested, however, and no flight-holes are visible, the attack is extremely difficult to detect, and experience indicates that a few boards of infested material commonly go into new buildings. It is therefore particularly important for the first few years to make very careful inspections, and as soon as any flight-holes or other evidence of attack becomes apparent, to apply a suitable treatment immediately, preferably the same day as discovered, so, as far as possible, to confine the attack to the boards originally infested. Particularly in the early stages of infestation, the adult common house-borer beetles tend to inhabit their exit-holes during the day and to lay the greater number of their eggs therein, so that the early detection of flight-holes is of major importance. Observations for new flight-holes should begin accordingly about October in the North and December in the South, and continue at appropriate times. Where old flight-holes are present, earlier signs of activity will be apparent from frass forced out of these by larvre working in the vicinity. Treatments in accordance with the following recommendations should be applied immediately.

TREATING-MATERIAI.S. There are numerous insecticides which possess some merit in the treat­ ment of timber a.gainst borer-attack, but many of them are highly poisonous and also dangerous both to the person applying them and to 9 the subsequent user of the timber. For these reasons the treatjng-materials recommended for general use have been limited to relatively harmless materials, but which, nevertheless, are sufficiently toxic and effective in their action. Those qualities which are held to be most desirable in such materjals are :- (1) The ability of the solution to penetrate into the timber. (2) The presence of a volatile constituent which, like the solution itself, is destructive to the attacking insects; and (3) A more or less permanent deposit which prevents future reinfostation. Water solutions are not generally favoured on ar.count of their swelling and other effects upon the wood. For either exterior or interior use, unpainted outhouses, &c., where its smell is not objectionable and may even be advantageous, as in the case of many farin outbuildings, creosote is undoubtedly the most effective material with which to treat wood against borer attack. Carbolineums are a special type of creosote, and, while quite effective, are usually proprietary pre­ parations costing more than standard creosotes. A good grade· of creosote should not cost more than about 3s. 6d. per gallon in gallon tins or 2s. 6d. per gallon in 4-gallon tins. Bulk prices are considerably lower. Creosote may also be used for the treatment of subfloor timbers of dwellings where its smell should not be too objectionable, but greater discretion is required "' in its use for roof timbers, since the heat generated under galvanized iron may be sufficient to make the smell objectionable. As creosote stains and discolours both paint and wood, it is unsuitable for use on painted and naturally finished or varnished wood, the paint, &c., not only preventing penetration of the preservative into the wood, but also staining badly if the creosote is injected into the flight-holes, &c. . For use on painted and polished woods, furniture, &c., a mixture com- posed of nine parts of a good grade of ·true turpentine and one part of kerosene is recommended. The kerosene content is limited on account of its softening effect upon certain finishes, its liability to stain light-coloured woods, its persistent odour, and the better penetrating-power of the turpen- tine. The staining, of course, is negligible as compared with that of creosote, which may he used in admixture, but for 11se on furniture any mixture containing a high proportion of either kerosene or creosote should be used with extreme care on account 0£ staining. Two other materials commonly recommended are ortho- and para-dichlorbenzene, the first a liquid and the second a white. crysta.lljne solid. They are non-inflammable. Either may be used alone or in mixture with kerosene, the solid form !"f usually .being more readily obtainable +.han the liquid. at a c_.ost of _abouy,c-...... ~/~ _ _ " 4R. 6d. per pound. The vapour from both has a not unpleasant odour and , /'-~""'', is non-injurious to man. / .·· / One of the most famous mixtures is that recommended by Professor Maxwell Lefroy as a result of his experience in the control of borer-infested buildings such as Westminster· Abbey. This consists of- Dichlorbenzene 50 parts (either ortho- or para-). Kerosene 4 7 parts. Barium oleate 3 parts. The foregoing are all in the nature of exterminating and repelling materials, usually applied ju the form of solutions to flight-holes, crevices, 10

&c. Where, in the case of valuable interior woodwork and furniture. it is also desired to eliminate signs of attack and still further protect the w·~od against reinfestation, the filling of crevices and flight-holes with some form of filler is recommended. A hard wax preparation -is usually employed for dealing with flight-holes on polished surfaces. It is prepared by melting in a metal pot one part of pure rosin and · adding three parts of pure beeswax, stirring and heating together. For flight-holes on unpolished surfaces, a liquid filler is usually employed, of which the following is typical:- Parts by Weight. Beeswax 1 Paraffin-wax, melting-point 140°-145° F. 3 Turpentine, with 10 per cent ..kerosene added 8 It may be prepared by mixing in a wide-mouthed bottle, in which the turpentine is first placed, the whole put in a basin of tepid water and the melted wax and rosin poured into it. The bottle should be corked and the contents well shaken. Every precaution should be taken against fire, and turpentine and kerosene handled at a safe distance from fire or naked lights. The preparation of these materials requires considerable care, as does also the choice and addition of a suitable • colouring agent to match the v:uious woods, and those desirous of informing themselves upon the details of the subject are therefore referred to a standard work(3) on the subject. ·

METHODS OF TREATMENT. General. The initial treatment should be made at those times when the larvre are coming towards the surface of the wood and forming their pupal chambers, but any subsequent flight-holes should be immediately treated as they appear, and a final treatment applied to the whole of the woodwork a few weeks after the appearance of the last flight holes made during the season. The initial treatment aims at the destruction of the larvre, thus preventing the emergence of the adult beet~es and the extension of their attack to other woodwork. This can be achieved only by thoroughly impregnating the infested wood, and while a spray or paint treatment should invariably be applied and is of value in making the surface unsuitable for the deposition of eggs laid by escaping beetles, it is largely ineffective as regards the boring larvre, which can be destroyed only by injecting a sufficiently large quantity of the various chemicals into old flight-holes and into specially made auger holes. (where possible) as to penetrate the borings, impregnate the wood, and finally poison the larvre. Except in very lightly attacked timber, a large quantity of the preservative is required to effect this, in the case of heavy attacks exceeding 1 gallon per' square yard of inch timber. While a hand pressure pump of the nature of a large hypodermic syringe is useful for the purpose, its use may necessitate considerable patience, and the employment of firms equipped with power-driven compressors and special injector guns may often be justified. Where the strength of any timber will not be seriously affected, large auger-holes may be made and filled with the preservative from time to time as it seeps into the timber. With small auger holes suitable 11 reservoirs or cups may be improvised to hold the preservative. It should be remembered that the preservatives seep along the grain much more rapidly and easily than across it, arid holes for injecting preservatives should, therefore, be as deep as possible and located with this in mind. In most cases the impregnation treatment should precede any general spraying or painting, as some idea of· its progress may be gained from the staining which spreads from the hole into which the preservative has been injected. In all types of superficial treatments it is necessary to pay special attention to cracks, crevices, joints, &c., so that the preservative penetrates these as thoroughly as possible. For this reason, in paint applications the preservative should be swabbed over joints, &c., rather than be merely painted on. The immediate treatment of new flight-holes is for the obvious purpose of killing any adult beetles which may be sheltering therein, and any new-laid eggs and their larvre. Likewise the final treatment aims at the destruction of the new brood of larvre. The former calls largely for an injection treatment, the latter for superficial treatments, particular attention being directed to joints, cracks, crevices, &c.

Firewood. Where live larvre of any kind are found in splitting open firewood and box timber, &c., the wood preferably should be burnt immediately, or, failing this, removed from the vicinity of all other woodwork and burnt before the emergence of the adult beetles. If this latter should prove impossible, then the wood should be isolated as far as possible from all other woodwork and liberally sprayed with creosote, although at its best this latter operation cannot be altogether effective.

Fencing-timbers, Garden Furniture, Outbuildings, &c. The treatment to be accorded such timber will vary with the intensity of attack and with its nearness to main buildings, &c. Where practicable, actively and heavily infested timber, especially in the vicinity of the main building, is best destroyed, preferably by burning, and observing the precautions recommended in the case of firewood. Creosote is the best preservative for unpainted exterior woodwork, and injection treatments, while desirable as the most effective, are seldom applied, resort being made to liberal applications by painting or spraying. The same treatment is applicable to unpainted interiors of outbuildings, whether lined or unlined. Painted woodwork is even more difficult to treat effectively, more especially when of a light colour. This necessitates either the dilution or the replacement of the creosote with kerosene, &c., and superficial treatments being almost useless, it must be injected by the means already described. Buildings. In some buildings the incidence of the attack may be so general and the depredations of the bettles so far advanced that any treatment is of doubtful value, but. in all cases of localized and selective attack the appropriate measures will fully repay the expenditure of, considerable time and money. Creosote, either alone or diluted with kerosene,, &c., according to the extent to which its odour is thought objectionable, may 12 be applied to sub-floor timbers. A thorough surface coating of all sub-floor timbers, either by spray or painting, is desirable even in addition to as thorough an impregnation as may be ·secured of the infested timbers. As previously indicated, the use of the creosote for roof and ceiling timbers is somewhat more limited on account of the greater heat in this part of the structure, causing the more volatile constituents of the oil to intensify the odour. Ortho-dichlorbenzene, either alone or diluted with kerosene, may be used in the same way for both sub-floor and inter-roof-ceiling timbers, and likewise crystals of para-dichlorbenzene, either dissolved in kerosene or, in the solid form, spread on the uppermost timbers or put into bags of " gunny" or butter muslin suspended from the highest point available. Alston(4) quotes 8 lb. to 10 lb. as being necessary per 1,000 cubic feet of ordinary ventilated space. Any of these treating operations in· confined spaces should be carried out only by the light of electric torches. Under no circumstances should naked lights be employed. For all painted and polished or stained woodwork, treatments are generally limited to injections with the turpentine-kerosene mixtures with perhaps small additions of creosote or the dichlorbenzenes, but the danger of staining from large admixtures of creosote cannot be over-emphasized, this oil being liable to penetrate the best of paint films and to show as a disfiguring stain. Even the turpentine-kerosene mixture may tend to soften some of the finer and older types of wood polish, which should be left untouched for several days after the treatment to allow rehardening.,

In ~he case of a new house. where the attack is confined to perhaps only one or two boards, thfiir removal ·is strongly recommended and should be seriously considered 1f at all practicable. Particular attention should be paid to attacks by the two-toothed long­ horn. It has already been stressed that the depredations of this insect may extend for several feet beyond the last flight holes; and that. other timbers in contact with the affected boards may also be infested. So destructive are the activities of these insects that exploratory borings or probings should be made in the vicinity to ascertain the full extent of their workings. Heavily-infested flooring should be removed immediately, and if the attack has spread to floor-joists, heavy injections of the various preservatives should be applied by the different means already described~ If the attack is at all advanced and widespread, it will require many gallons to deal thoroughly with the infestation. Care, however, should be taken that the preservative does not leak out of other flight-holes while being applied. They should be blocked up by wax preparations or putty, &c. Preferably, timber badly attacked by this insect should be renewed and the removed timber at once burnt.

F'urniture. As in the case of other timbers, injection treatments provide the soundest remedy for borer-attack. Pressure injections may be made through :flight­ holes both on polished and other surfaces while seepage holes and cups can usually be arranged on unseen surfaces by turning the furniture upside down and on its sides, &c. The turpentine-kerosene mixture finds the widest application, although the dichlorbenzenes may be used in admixture. i3

It may also be possible to use a very small proportion of creosote for very dark-coloured woods, but its staining effect must always be borne in mind. The finished surfaces should be left untouched for several days after treat­ ment and before polishing. In addition to the injection treatment, a.11 unfinished and unseen portions should be given a superficial treatment, for which a certain proportion of creosote may often be usyd. The preservative should be worked into all joints, crevices, cracks, &c. Where plywood backing, &c., is badly infested, its removal and destruc­ tion by burning is recommended as it usually involves only .a simple operation. A number of plywoods are now reported as being treated during course of manufacture to resist insect attack. The final treatment of plugging flight-holes with wax fillers constitutes an art in itself, and those desirous of becoming proficient are referred to a standard work on the subject (3). The liquid filler previously recommended can, however, be used for filling up crevices, cracks, and gaping joints in unexposed parts merely by pushing into place with a flexible putty knife or similar instrument.

Handles, &c. Handles and other small articles are most easilv treated by immersion in one of the appropriate solutions recommended. · ·

CoNCLusrnN. The foregoing discussion should assist to bring the subject of borer attack of timber in buildings and furniture into proper perspective, and to reassure owners as to the practical possibilities of remedying any damage which has already occurred and of preventing future infestations. While, admittedly, no complete solution of the borer problem is possible on a national scale without similar hygienic precautions on the part of sawmillers, timber-merchants, and manufacturers and importers of wooden articles, &c., and without compulsory burning of infested timber from demolished buildings, &c., a marked reduction in the prevalence of borer-attack is possible by individual efforts of home-owners, and it is the purpose of this report to stimulate such action and facilitate the appropriate measures required. 14

APPENDIX.

COMMON AND BOTANICAL NAMES OF SPECIES MENTIONED IN PUBLICATION.

Softwoo~s. Californian red wood -(Sequoia sempervirens). Corsican pine .(Pinus laricio). Coulter's pine (Pinus Ooulteri). Digger pine (Pinus Sabiniana). (Pseudotsuga taxifolia). Firs (Abies spp.). Hoop pine (Araucaria Ounninghamii). Insignis pine (). Jeffrey's pine (Pinus Jeffreyi). Ka uri ( australis). Kawaka (Libocedrus Bidwillii). Larch (Larix decidua). Macroca.rpa (Oupressus macrocarpa). Maritime pine (Pinus Pinaster). Matai (Podocarpus spicatus). Miro (Podocarpus ferrugineus). Norway spruce (Picea Abies). Pines (Pinus spp.). Pitch pine (Pinus palustris). Queensland kauri (Agathis robusta). ,Rimu ( cupressinum). Scots pine (Pinus sylvestris). Silver pine (Dacrydium Oolensoi). Spruces (Picea spp.). Torrey's pine (Pinus Torreyana). Totara (). West Himalayan spruce ( Picea M orinda). Western red cedar (Thuja plicata). White pine (Podocarpits dacrydioides). 15

Hardwoods. Ash (Fraxinus spp.). Broadleaf (Griselinia littoralis). Grey gum (Eucalyptus punctata). Grey ironbark (Eucalyptus paniculata). Hinau (). Horse chestnut (Aesculus Hippocastanum). Kohekohe ( spectabile). Mahogany ( spp.). Native beeches (Nothofagus spp.). Oaks (Quercus spp.). Pukatea (Laurelia novae-zealandiae). Rewarewa (Knightia excelsa). Rosewood (Dalbergia spp.). Spotted gum (Eucalyptus maculata.) Sweet chestnut (Castanea sativa). Sycamore (Acer pse11,doplatanits). Taraire (Be1:lschmiedia tarairi). Tasmanian stringybark (Eucalyptus obliqua). Tawa (). Walnut (.luglans spp.). (Salix spp.).

REFERENCES.

(1) MILLER, DAVID: Forest and Timber Insects in New Zealand. N.Z. State Forest Service Bull. No. 2, 50-51, 1925. (2) RouGHLEY, T. C., and WELCH, M. B.: Wood-borers damaging Timber in Australia. Technological Museum, Sydney, N.S.W. Bull. No. 8, 25-27, 1923. (3) Gmnwoon, JOHN: Worms in Furniture and Structural Timber. Oxford University Press, London, 1927. (4) ALSTON, A. M.: Beetles damaging Seasoned Timber. William Rider and Sons, Ltd., London, E.C. 4.

G. H. LONEY, Government Printer, Wellington-1934. [1,000/10/3t-9295