NEW ZEALAND FLAX.

Manawatu Herald, Volume XXXIX, Issue 1738, 17 July 1917, Page 1

NEW ZEALAND FLAX.

• PESTS AND DISEASES. PROGRESS OF THE INVESTIGATION. [By D. Miller, Entomologist, in the N.Z. Journal of Agriculture.] Some time ago the New Zealand Flaxmillers’ ’ Association drew the attention of the Government to the serious damage being done to tlax areas by a grub, and as a result of their representations an officer was appointed to investigate,, and the following is the lirst report in connection with the matter: — An investigation into the lifehistory and possible control of Xanthorhoo praefectata, the larvae of which damage the leaf and fibre of New Zealand tlax (Phormium ■tenax), was commenced during February, 191 G, As had been anticipated, the investigation was extended to comprise other insects which incidentally were found to do considerable damage to the /lax. Certain fungus diseases and other troi utiles of (bo (lux-plant also receiv[ed attention. The matter of the present article is mainly a summary j of tlie evidence collected during the I investigation up to the end of April I of this .year. It may bo slated preliminarily that the phorminm-fields fall into two main classes —(1) the swamp areas, and (2), to a lessor extent, (he hill areas. In the latter class is included the mountain-flax (P, Codkianum), which, though at present of no commercial value, will be referred to later on in connection with the attacks of larvae. Practically no hill areas cut for fibre exist in (be North Island, but in Southland they predominate, in places covering the ridges and steep faces of the low hills. The flax of these areas grows in its natural state, but the swamp areas of, the North Island have been drained—sometimes, as will be seen, overdrained —in order to procure a dense growth of tlax. Most of the swamps are at or about sea-level, an exception being the area at Lake Tutira. Flax varies considerably In colour, height, and shape of leaf, but no systematic arrangement of these variations has yet been published. On the whole the leaf of Southland is more rigid and takes longer to mature than that of the North Island, where more variation occurs, and it appears that tlax growing in moist or areas is of a darker shade of green. As far as is known, however, variations do not bear directly upon the attacks of larvae. In the North Island, as a rule, the tlax is cut every third or fourth year, and the fibre is considered not so hard as that of the South Island, where the leaf is not cut so frequently. However, (he average amount of leaf required to produce a ton of fibre does not usually vary to a marked extent. During growth (he young shoots arise from the centre of the plant, so that the outer leaves of a “fan” are the oldest, and commence to die off at the age of approximately one year and three-quarters. When withering the loaf turns inwards longitudinally along the edges, and in time forms a more or less hollow lube. These dead leaves, which either form accumulations around the plant or are supported by the green leaves, arc of considerable importance in Ihe propagation of larvae, and will be referred to hereafter as “leaf-tubes.” The term “flax-grub” is generally applied in a vague sense to those larvae (and even fungi) which attack the flax-leaf, but at present the larvae of the three following species of Lopidoptera will be dealt with; Xanthorhoo praefectata Walk., Melanchra steropastis Meyr., CEceiicus omnivorus Fereday. Of these, Xanthorhoo and Melanchra are the most prevalent, and do most damage; CEceticim is only occasionally found. XANTHORHOE PRAEFECTATA. The larvae of Xanthorhoe attack the lower epidermis of the leaves, removing long and narrow strips of varying dimensions and exposing the fibre, which soon decays. Rarely do these larvae attack the upper surface of the leaf. As a rule the epidermis is removed parallel to the fibre, but occasionally either in a transverse or sinuated manner. While eating the larva works backwards, and will move its head from side to side, thus at times making a cut much wider than its head; or, again, the cuts may be, so narrow as to be almost unnotieeable. During the day the larvae are to be found sheltering in the dry leaf-tubes, and several specimens may be taken to[Continued on Page 4.]