WOOD BORERS.

Auckland Star, Volume LVII, Issue 78, 3 April 1926, Page 17

WOOD BORERS.

THE DIFFERENT SPECIES, j IMPORTED INSECTS WORST. PROTECTION OF TIMBER. ; i - •_ c In an address to the council 01 tne -j Xew Zealand Forestry League. Mr. D. £ Miller. Entomologist to the Department 1 of Agriculture, gave some interesting m- j formation on the subject of wood borers. , He sard: h "In this country, where timber is so } extensively utilised in building construe- t tion. protection pf timber from the at- ■ tacks of boring insects should be of first ; importance. There are few places iv ; Xew Zealand, however, where some : species or other of boring insect is not ; established, and -causing considerable : damage to milled timbers. Indeed, the annual financial loss due to the presence i of borers is needlessly great, since no co-operative attempt is made to hold : the insects within reasonable control. Naturally, borers are forest dwellers, different species attacking the living, dying, or dead trees. The location of the borers in the tree varies with the species of insect, some infesting the , bark, some the sapwood, and others the heart. Those species attacking only the living. or dying tree are _no longer present after death, though their j borings remain and result in the so- ; called "pin-hole" condition, of milled . timbers, the value of which is there- , fore reduced. Just as naturally-killed trees in the forests are attacked by j borers attracted to dead wood, so milled j timber is artificially brought to a simi-, lar conditio* favourable for infestation I iby these insects: It is against the latter , I species that protective measures should be adopted in the case of milled timbers. ■ The insect, food value of felled or | milled timber is dependent upon the j species of tree and the chemical com- j position of its various parts; thus not only are some species of woods more liable to attack than others, but also , different parts of the same species. The' presence of micro-organisms .in the j wood is also essential to tbe well-being j of certain borers, since by the action j of these organisms cellulose is converted ' to .proteins, etc.. most nourishing. to the insects. The fact that resin*, I etc., may be stored by the tree in the heart wood renders the latter of many j species resistant to borers. i Origin of Borers in New Zealand. i The boring insects occurring in Xew i Zealand either are (1) Xew Zealanders themselves or (2) have been accidentally introduced from other lands in imported I wood. An example of a destructive I Xew Zealand borer, the two-toothed j long-horn beetle may be taken. This insect is of the '"hu-hu" type, but smaller. Xaurally. the larvae bore in dead wood in the forests, but of late years seasoned timbers in buildings and furniture have been extensively attacked and considerable damage done- This insect is brought from its natural breeding grounds in firewood especially, and when this is stored for use either in or near dwellings an excellent scource of infection is established. However. there is not so much to fear at present from the native borers of dead timbers as from the introduced species. Perhaps the best known example of these forms is the common house borer (Anpbium); this insect attacks a great variety of timbers, kauri, totara, . and oak' not . excepted, though attacked to a less extent than others, e.g., white pine. Sapwood is more susceptible than heart wood. but the beetle is active almost equally both in badly ventilated . and dark situations. Imported timber very often shows signs of insect attack. Though in many cases the injury has been caused by beetles v.o longer present, but which attack the still living timber, there are times when living beetle larvae are actively at work in the wood on its arrival here. Perhaps the most important example at the present time of such importations is that of hardwood poles from Australia. One does not need to have specialised in insects to realise this. Even the waterside workers are aware of its importance, and make use of it. On the - arrival of a shipment of poles these men may be seen removing from the poles large beetle grubs, that often ocUr- in thousands, in order to use them for fishing bait. These insects are mainly eucalyptus feeding ones, but others not so restricted in their diet are also brought to the Dominion in this way. The, further distribution of these insects throughout the land is rapidly brought about by the railing of the poles to all quarters. Herein initial difficulties of possible establishment—time, natural barriers, and distance —are . rapidly overcome. If it is necessary to have these poles, is it essential that many of them should be cut from over and immature or insect injured trees? Coatrol of Borers. The aim of-control is not extermination, but reduction to a point where the damage does" not seriously affect market values. There are two points from which the problem should be at- ' tacked. ' (1) Organised co-operation by those ' associated with the handling of timber in Xew Zealand to prevent infestiation - as far as possible by borers already prevalent in the country. (2) The necessity for only sound ' timber being imported. ' One of the factors responsible for ; the spread of borers in Xew Zealand ' is the practice of utilising timber for ; construction or firewood from eon- • demned buildings. It should be the duty ■of all sawmillers and timber mer- ■ chants', as well as owners of wooden ' buildings, to prevent accumulation of " disused' timber about their premises; 1 such timber harbours borers, is a ; -constant source of infestation, and should be destroyed. Since timber is ' more often attacked in _ ill-ventilated • situations, buildings should be con r structed to allow a maximum air circulation. Further, timber should be stacked in such a way as to give access to as much air and light as possible. The use of as much heart wood as possible and the avoidance of soft ■woods, such as white pine, reduces chances of borer attack. The treatment of wood, even sapwood, with creosote, Will not only prevent borer attack,-but also decay. It has ■ been found that when creosote is applied 5 warm its presevative powers have stood for 25 years.