ENEMY OF TIMBER.

New Zealand Herald, Volume LXIV, Issue 19727, 29 August 1927, Page 11

ENEMY OF TIMBER.

THE HORNTAIL PROBLEM. POSITION OF HEALTHY TREES. LITTLE CHANCE OF DESTRUCTION After an extensive tour of New Zealand forest areas and a thorough investigation of the possibilities of menace from the giant horntail, Mr. Owen Jones, forestry administrator for New Zealand Perpetual Forests, Limited, is convinced the Dominion has little to fear from the pest, provided forest trees are kept in a healthy condition. Mr. Jones said there was no doubt the horntail was established in New Zealand. It was first recorded 27 years ago and was widely distributed, occurring in Marlborough, Canterbury, Wairarapa, Waikato, Rotorua, and elsewhere, but it did not appfiar to attack trees that were thoroughly healthy and vigorous. A European authority had stated it preferred weakly trees which had been injured by deer, lightning or wind, and it never attacked rotten wood or perfectly sound standing trees. " This agrees closely with observations made in the course of my trip," said Mr. Jones. " All the infested trees seen were more or less weakly, suppressed or sickly and, as in Europe, were in l he pole stage." The pest did not appear to attack very young trees under the age of 10 years. Many of the badly infested trees seen were lying or dead, but it was doubtful whether the horntail was the primary cause of this. It seemed more probable that in most cases it had only hastened a process already begun. Although the insect was dangerous, owing to the large amount of food available for it in concentrated areas in New Zealand and the comparative absence of its natural enemies, there was no cause for panic provided suitable steps were taken. In Europe, although the horntail sometimes did considerable damage, it was not regarded as a major pest, and it should not become one hera.

Regarding the question of how to check, control, and diminish the attack of the insect, Mr. Jones does not agree that no chemical or mechanical control is possible and that the only hope lies in the introduction of parasites. " The matter, as with most cases of insect infestation, could be largely met by'silvicultural measures," he said. " The horntail will not, as a rule, attack healthy trees, and consequently its depredations could be very largely controlled by the periodic removal of all sickly, weakly trees and the maintenance of plantation areas in a sound condition." Dealing with the general question of the introduction of insect pests and their control, Mr. Jones said there were two aspects to be considered. First, insect pests were bound to be introduced sooner or later, and once established they could not be entirely eliminated. The pests could be introduced through so many, various, and frequently inconspicuous channels that their entire prevention was impossible. A great deal could, however, be effected by a careful system of inspection and quarantine. The existing system was inadequate, the importation of hardwood poles from Australia, which were frequently heavily infested with wood-boring insects, providing an example.