BORING INSECTS.

Press, Volume LXII, Issue 18672, 22 April 1926, Page 4

BORING INSECTS.

ATTACKS ON TIMBER. ADVICE OF ENTOMOLOGIST. Some valuable information was given recently by Mr Miller (entomologist to , the Department of Agriculture) in an address to the Council of the New Zealand Forestry League. He said:— "In this country, where timber is so extensively utilised in building construction, protection of timber from the attacks of boring insects should be of first importance. There are fow places in New 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 of borers is needlessly great, since no co-operative attempt is made to hold the insects within reasonable control. "Naturally, borers are forest-dwell-ers, different species attack the living, dviug, or dead trees. The location ot the borers in the trees 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 alter death, though their borings remain and result in so-called 'pinhole',condition of milled timbers, the value of which is therefore reduced. "Just as naturally-killed trees in the forests are attacked by borers attracted to dead wood, so milled timber is artificially brought to a similar condition favourable for infestation by these insects. It is against the latter 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 species of tree and the chemical com T 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 wood is also essential to the well-being of certain borers, since by the action of these organisms cellulose is converted to proteins, etc., most nourishing to the insects. —The fact that resins, etc., may be stored by the tree in the heart wood renders the latter of many species resistant to borers. Origin of Nuisance. . "The boring insects occurring in NewZealand either are (1) New Zealanders themselves or (2) have been accdentally introduced from other lands in imported wood. "An example of a destructive New Zealand borer, the two-toothed, longhorn beetle may be taken. This insect is of the 'hu-hu' type, but smaller. Naturally the larvae bore in dead wood in the forests, but of late years season--I ed timbers in buildings and furniture have been extensively attacked and considerable damage done. This insect is brought from its natural bleeding-1 grounds in firewood especially, an.l when this is stored for use either in or near dwellings an excellent source of infection is established. "However, there is not so much to fear at present frofn the native borers of dead timbers as from the introduced species. Perhaps the best known example of these forms is the common house borer (Anobium). This insect attacks a great variety of timbers—kaliri, 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 no 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 gentlemen may be seen removing from the poles large beetle grubs, that often occur in thousands, in order to use them for fishing bait. These insects are mainly eucalyptus feding 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 i.s 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 overcoine. If it is necessary to have'these poles, it is essential that many of them should be cut from over and immature, or insect injured trees. Preventing Infestation. "The aim of control is not exterinination, but reduction to a point where tho damage does not seriously aifect market values. There- are two points from which the problem should be attacked: (1) Organised co-operation by those associated with the handling of timber in New Zealand to prevent infestation 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 New Zealand is the practice of utilising timber for construction of firewood from condemned buildings. It should be the duty of all ••awmillers and timber merchants, as well as owners of wooden buildings, to prevent accumulation of disused timber about their premises; such timbers harbour borers, is a constant source of infestation and should be destroyed. Since timber is more attacked in illventilated situations, buildings should b« constructed 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. Tho 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 warm its preservative powers have stood for 20 years."