THE HEMP INDUSTRY.

Manawatu Herald, Volume XLI, Issue 1938, 11 February 1919, Page 3

THE HEMP INDUSTRY.

YELLOW LEAF DISEASE,

PAPER AT SCIENCE CONFERENCE.

At the Science Congress at Christchurch an interesting paper was given by Dr. L. Cockayne, F.R.S., and Mr A. H. Cockayne, Government Biologist, and its subject was “The Yellow-leaf Discase'in relation to the Flax Industry.” Regarding this industry they remarked

that the area devoted to flax extended to some 40,000 odd acres, from which annually some 25,000 tons of dressed lihre and 4,000 tons of”tow were produced. For the manufacture of this material over 200,000 tons of flax leaves were cut each year. At £25 per lon for flax fibre, which could he taken as about (he average normal price, the industry was worth about three-quarters of a million pounds annually, .which meant that each acre of flax produced each year almost £2O. Such a return exceeded that from that of any other type of soil utilisation, except those of the most intensive character, such as fruit and vegetable growing. The dairy cow on the richest pasture, marvellous as she was in the conversion of plant products into marketable commodities, had to take second place to flax, so far as production per unit area was concerned, dust as the flax areas played an important purlin the production, so also were they important from a population supporting standpoint. The employment, of at least one man to each 25 acres was by no means unusual, and (his compared more than favourably with even dairying. Not only did the .(lax farmer employ labour largely, Imt lie employed it permanently, and at a rate considerably in excess of (hat paid for any oilier type of permanent farm labour, il had been contended (hat the actual milling of (lax was distinct from the growing of flax, bat (Ids was not so, and before anything else, (he flux miller was a Jinx farmer. It was jus( this i oiiversiou of (he miller from an ephemeral exploiter of a natural resource (o a permanent farmer of a national industry that had made (tax-milling, so long as the production of leaf could he carried out, a permanent and important national asset. These points being considered, it was (dear that any factor likely to limit the output of flax should be viewed with grave alarm. The threatening aspect of yellow-leaf disease was therefore a matter of grave concern not only to the individual miller, but to the country as a whole.*

It was pointed out that the flax areas wen 1 in the main located on swamj) land, which, although of high fertility in certain directions, and potentially valuable for other phases of soil utilisation, were not yet suitable for such purposes. The ureas could be looked upon largely as soils in the making, and it was remarkable that such returns as were secured were possible on such land. The speaker voiced the opinion (hat provided disease could he eliminated much swamp land (had at present was being more or less unsuccessfully converted into grassland, should he put through a (laxgrowing phase before such work was attempted. Probably the most wonderful and, from a scientific standpoint, the most interesting tealure of much of our (lax areas was that they had been derived from raupo swamp containing little flax to pure stands of phormium, and this by mere process of draining away the permanent surface water of the swamps. Dealing specially with the yellow-leaf disease, the speakers mentioned that their remarks referred almo.-t entirely (o the great Makerua flax areas, which produced (dose on two-thirds of (he llax fibre milled annually. In that district yellow-leaf had appeared on a certain block some three years ago, and at first occasioned hut liltle notice, as similar outbreaks strictly limited (o small isolated areas of excessively wet ground had been known for many years. In (his case, however, (he affection had spread rapidly, and at (he present time there was hardly an area in the North or South Island that was not affected to a greater or less extend Yellowleaf was characterised hy the premature yellowing and stoppage of growth of (he outer leaves of the fans. In eases of severe attacks the whole plant would die, Iml in general the effect' was to reduce the production of millahle leaf to such an extent as to render cutting almost impossible. It was only in one or two areas where really extensive damage had been done. The rapid and disastrous results (hat had followed attack in one particular instance whore the output had been reduced 75 per cent., however, gave clear warning of what might happen. In the early days of the investigation it had been held that soil conditions wore the primary causes, but work' recently carried out by tint Department had to a large extent upset this view, and showed that a fungus was invariably present in the roots of affected plants. Whether or nol this fungus was really the cause had nol yet- been properly postulated, but (here seemed little; doubt that it was the causal agency. In many re.-peets this fungus closely resembled one that produeed similar results in acid soils on the cotton, and which was partly responsible for the reduced output of that commodity. Affected flax plants invariably possessed an excess of roots rotting away before they had completed their normal life. A peculiar feature, but one that could easily ha explained by the small development of healthy roots, was that affected plants when cut produced healthy

leaves for (lie first few months. As soon, however, as the production of leaves exceeded (he required amount, of water that the impoverished root supply could furnish, the outer leaves turned yellow, and the worse affected were the roots the sooner would this condition arise. - The difficulties attendant on the adoption of any control measures were outlined. Il was, however, suggested that even if the disease became impossible to control in the present flax areas a proper selection of immune races, which from observations appeared lo exist, would again bring the industry on a proper tooling. If such u course became necessary it would be necessary lo deal with (he plant along properly cultivated lines, and Ihe high returns possible appeared to make such a proposition a perfectly sound one.