ENEMY TO TREES

New Zealand Herald, Volume LXXI, Issue 21830, 19 June 1934, Page 14

ENEMY TO TREES

THE HORNTAIL BORER EXPERTS' VARYING VIEWS EFFECT ON EXOTIC FORESTS Is the horn tail borer, a pest which is very prevalent in tho exotic foi est plantations of Canterbury, a serious menace; and arc tho authorities who control afforestation taking adequate steps to prevent the spread of tho post and others of its 'kind? is a question that is being discussed in Christcliurch. Experts seem "to differ on both questions. An experienced entomologist, Mr. F. Morrison, of Canterbury College, says that many largo plantations aro swarming with tho borer, which he thinks might in time become a menace if not controlled. Ho condemns the controlling authorities generally for taking what he thinks is a shortsighted view of afforestation practice. On tho other hand, the conservator of State forests in Canterbury, Mr. W. G. Morrison, says he thinks that the horntail borer presents no serious threat to the commercial future cf tho exotic forests, particularly in the State forests, where a closo watch, is always kept on such pests. Both experts were asked by tho Press last week for an opinion on the subject, following the contention of a Christchurch business man that rather than dismiss men engaged in labouring work in the forests, the State Forest Service would bo better advised to employ tho men on ordinary rates of pay in .cleaning the plantations of such pests as the borer. Ho exhibited a piece of pinus radiata badly riddled by 'the borer as an example of the condition of- 1 much of the smaller timber growing in somo of the Hanmer plantations. Care oi Plantations Mr. F. Morrison stated that from the point of view of the entomologist the contention was sound. Majjy of the South Island plantations were so badly looked after that they swarmed with pests and were the breeding grounds of dozens of them. The horntail borer itself, which was swarming in the forests at Hanmer and could be found very prevalent in the Burke's Pass and Nelson plantations, and even at Bottle Lake, near Christchurch, might not at present bo a menace to the forests. The present habit of this borer, it was stated, was to attack living but weak and diseased trees or dead timber. Its most frequent victim at the present time was pinus radiata. But it had attacked most of the pines and had even been discovered boring into the rimu weatherboards of a building. That indicated that the pest could possibly extend its range. It was a comparatively recent introduction to New Zealand and it might eventually suit its habits to life- in strong and healthy growing trees. "We do not understand how to look after our forests in New Zealand along tho lines adopted in such countries as Germany, Scandinavia and Great Britain," said Mr. Morrison. "In fact, it is high time that it was decided here that if exotic trees are to be grown, they must be looked after in the proper fashion by experts. In many of the exotic plantations dead and decayed trees, weak growths, broken limbs and wind-blown trees are left to become breeding grounds for all sorts of pests. It is a short-sighted policy to establish a plantation and then leave it to look after itself, just as if it were a native forest." Introduction of Parasite , The conservator of State forests denied that the State plantations were not adequately cared for. Men were actually employed on the very work suggested, and all trees affected by tho horntail borer and ether pests were cut out as soon as the presence" of the pest was detected. As an additional measure in the campaign against the borer there had been liberated at Hannter a number of the parasites which the Cawthron Institute introduced. The liberation had been made some years ago and there were signs that the parasite was spreading at Hanmer. Probably, said the conservator, the parasite would be able to deal with the pest effectively. In the State foreststhe policy was not to' leave the trees to care for themselves. The service employed its own entomologist, who inspected and reported immediately on any disease discovered. The principles of silviculture were adopted throughout the work of the service. Dead trees were cut out and all steps possible were taken to prevent the breeding or spread of the pests. Neither in the State forests nor in the private plantations in Canterbury had the borer assumed the proportions of being a menace. The borer attacked weak or dead trees—timber which would have to be cut out in any case. It would attack any dead trees or timber, but not the green and healthy members of the forest. Mr. Morrison said he did not entirely agree with the suggestion of the entomologist that perhaps the horntail borer could adapt itself to attack and thrive in strong and healthy trees. It was perhaps possible that'the insect could change its habits, but its existence had been known for many ccnturies in the Northern Hemisphere and it had not been known to develop along the lines mentioned.