NASSELLA TUSSOCK

New Zealand Journal of Agriculture, Volume 63, Issue 2, 15 August 1941, Page 91

NASSELLA TUSSOCK

Nassella tussock has become a very serious menace in the Waipara County, Canterbury, and a comprehensive survey is being made to determine the most effective control measures

and to decide on a concerted line of action. A description of the characteristics of nassella and a plan of the survey are given in this article.

Survey To Determine Most Effective Control

By

DR. H. H. ALLAN,

Director, Botany Division, Plant Research Bureau, Wellington.

IN 1928 Mr. R. McGillivray, then Fields Superintendent, Christchurch, found an unknown tussock grass, of rather handsome appearance, on a farm at Waipara. He and his officers made a somewhat detailed examination, and found the grass to be well established near Waipara township, with more isolated occurrences elsewhere in the county. Inquiries have failed to elicit definite evidence as to how the plant first came to be naturalised in the district, although various suggestions have been made. It seems certain that the first appearance was some forty years ago. Because of its similarity in growth-habit to native tussocks, especially hard tussock, its spread in the earlier years was probably more or less overlooked. ’ / In 1934 specimens came into my hand, and the plant was identified as Nassella trichotoma. The small South American genus Nassella is closely . related to the needle grasses (species of Stipa), and occurs in Peru, Chile, Uruguay and Argentine. Our species is a widespread and characteristic plant of the Argentine pampas country. Dr. L. R. Parodi, the distinguished agrostologist of Buenos Aires, informs me that in its native haunts the grass is not eaten by stock, except when nothing else is available. In the highly cultivated areas it is easily controlled, and is there now found only in waste places, such as along roadsides and railway lines. Because of its “tumble weed” habits it is known as the “flying straw” (paja voladora). Species of Nassella have reached Tweedside and Montpellier in wool from South America, and it is possible that this was the method by which the grass reached NewZealand. Stipa neesiana, a related, harmful South American grass, has been noted near wool factories. in Scotland, France, Italy and Germany, and has recently been observed near Auckland. ' In the Waipara County the grass has become a very serious menace. At the request of the Omihi branch of the Farmers’ Union, the Plant Research Bureau Committee

asked me in November, 1940, to visit the area under the guidance of Mr. McGillivray and arrange for a survey to be made. After preliminary investigations and discussions with t|ae farmers concerned, an interim report was furnished, and arrangements were made for a more detailed examination. This could not be done at once, as the officer deputed for the work was on military service, but further examination of part of the area affected was made. The Minister for Agriculture visited Waipara early in May, 1941, and met representative farmers, and saw some of the badly infested areas. As a result he promised that a survey should be undertaken at once. Mr. R. P. Connell, Acting Fields Superintendent, Christchurch, and the writer, who had accompanied the Minister, drew up a plan of work, and Messrs. A. J. Healy, Botany Division, and P. Barrer, Department of Agriculture, are now engaged on the survey. They have already found that the tussock is even more widely spread than was known.

Characteristics Of Nassella

An adult plant, growing 1 free to develop fully, . forms a dense tussock, with a fairly deep rooting system, a base of some six inches in diameter, a height of 20 inches, and a spread of 18 inches or more. At flowering time numerous inflorescences are produced, reaching about 40 inches in length. The foliage • is very fine, harsh and tough, bright green and erect when young, paler and drooping when older. There is usually much dead, slowly decaying foliage covering the ground at the base. The flower stalks are slender and much branched above, with ■ the final spreading branchlets each' carrying a single flower, recognisable by the long, slender bristle terminating the seed and the purplish colour. An average plant will bear approximately 1,000 seeds. At maturity the whole inflorescence, ,with the seeds attached, separates from the plant, and acts as a “tumble weed”— is, it is blown for long distances along the ground until it is arrested by some obstacle. During strong winds it may be carried high in the air for still greater distances. The essential features which make the grass objectionable are: (1) The fine, harsh, tough, fibrous, inedible foliage. ( (2) The capacity to grow in extremely dense communities, to the practical exclusion of other herbage.

(3) The power of seedlings to develop even in dense areas, and to replace old and decaying tussocks. (4) The mat of dead foliage ■ and flower stalks accumulating between the tussocks, aiding in killing out or preventing the establishment of other plants. 7 , (5) The prolific seeding habit and apparent powers of the seeds to remain viable for long periods. (6) The tumble-weed habit of the inflorescence, which, . coupled with its lightness, enables the seed to be spread in quantity for great distances.' (7) The power of the seedling to establish under shade, maintaining the dense cover once it is established. (8) The power of the seedlings to establish in all but the densest pastures. ; (9) The long bristle and the pointed base of the seed, enabling it to penetrate the wool of sheep. (10) The resistance to control by methods hitherto devised.

Comparison with Native Tussocks

As it is most important for all concerned to be able to distinguish the different tussocks, the accompanying table has been drawn up, which should be read in connection with the illustrations. A description of needle-grass

(Stipa variabilis, naturalised from Australia) is included, as this pest (the seed is injurious to sheep) is well established near Waipara, especially on stony riverbeds. It has been sometimes mistaken for young Nassella. Needle-grass is at once distinguished by the small size and the very long

bristles of the seed, bent at an angle. Young plants of Nassella can be distinguished from those of needle-grass by the absence of the long hairs at the point where the leaf joins the stem. Silver tussock can be distinguished at all stages by the leaves not feeling rough when they are rubbed down-

wards between finger and thumb. Hard tussock, or fescue tussock, and Nassella are less easy to distinguish in the young stages, and a close examination of the leaf differences is necessary until experience is gained.

Area Occupied

The area at present under attack by Nassella is extensive, but the survey has already shown that infestation in the Cheviot county is more severe than had been reported; Isolated plants have been noted near Saltwater Creek, just north of Ashley. The most extensive area at present known to be severely affected is that near Waipara township and extending on to the western slopes of the coastal hills on both sides of the Waipara river. Less extensive densely infested areas occur near Scargill, Motunau, and elsewhere in the Waipara county.

Plan of Survey

The following is an outline merely of the plan of survey being followed, which is subject, of course, to modification as the work proceeds. (1) Close survey of the areas known or reputed to be under attack and

adjacent areas. Reconnaissance survey of neighbouring country. (2) Comparison of infestation on arable and on pasture land, with study of the nature of the ground and aspect most open to invasion, including study of limestone and non-limestone areas. (3) For the purpose of the survey the Waipara county and parts of the Kowai and Cheviot counties have been divided into blocks, and the nature and degree of infestation will be mapped out on each. (4) The results will be classified under the headings: (a) Areas so badly affected that they are out of production or are under distinctly diminished production. . (b) Areas seriously, but more lightly, affected. • > . ' (c) Areas with only small, local occurrences. (d) Areas free, but liable to early invasion. (5) General information will: be gathered by consultation with farmers and by observation as to methods of control adopted, the degree of success gained, the relative proportion of the holdings attacked, the relation of at-

tack to, methods of farming, the topography of the country, and the location and extent of plantations and shelter belts. . ' (6) Gathering data affecting the possibilities of afforesting the worst areas. (7) Examination of the incidence of nassella in temporary pastures and the lucerne stands. (8) Observations on the relative importance 'of the various ways in which the tussock may be spread.

t tempted Control Measures

Efforts at control have so far been confined to a few areas, and have met with but little measure of success. (1) Burning.— lndications are that a fierce fire is needed, and that the tussock rapidly recovers. Often, the centre is burnt out, but a ring of growth shoots up from the margin, while small tussocks may be little affected. Burning , also opens the ground to the growth of seedlings and fresh invasion of seeds. These are disadvantages, even when no more is attempted than preventing the plants coming into flower. On some burnt areas late flowering has been noted.

Careful controlled experiments should be made before any general recommendation to butn is made. (2) Grubbing.— This has been tried on many areas, with conflicting opinions as to the result. I have observed many tussocks killed by this method, but there is some evidence that the disturbance to the soil hastens the germination of seed already shed on the ground. It is certain that in areas long subject to the grass, the seed content of the soil may be high. Tussocks that have been grubbed too deeply have been noted to recommence growth. It is, however, a useful method of control in newly-attacked areas of no great extent. (3) Cultivation. lt appears to be generally accepted that ' the tussock can be controlled quite well in cultivated land by the ordinary, methods of procedure. Cultivation on the hill country, however, where it is possible, is inadvisable at such frequent intervals as would be needed to control the tussock. The dangers of too frequent, cultivation on such country is shown by the erosion already setting in on certain areas. . (4) Insect Attack. — Several caterpillars have been noted feeding on the tussocks, weakening and killing the growth in the centre. No evidence of any real control has as yet been noted,

and in areas where the silver tussock is still plentiful this would also be liable to attack. ’ (5) Pasture. really dense pasture delays the entry of the tussock, but is, of course, difficult to obtain and maintain on much of the hill country. (6) Sprays. But little effort has been made to control the tussock by the use of sprays, and no certain evidence is available as to the possibilities of success on these lines. (7) Plantations.— Plantations and shelter belts, especially those with a somewhat dense bottom growth, aid in checking spread, and careful consideration will have to be given to the

proposal to afforest the worst areas. The plan appears sound on areas that are already practically out of production. ' / .

Conclusion

It will be clear from the above that after the completion of. _the present survey it will be necessary to consider all the problems raised to determine on a concerted line of action and see that it is carried out. The massed battalions now in the field will not be rolled back by spasmodic and haphazard efforts.

NASSELLA (A. trichotomy) Fig. 1. HARD TUSSOCK (Festuca novae-zelandiae) Fig. 2. SILVER TUSSOCK (Poa caespitosa) Fig. 3. NEEDLE-GRASS. / (Stipa variabilis') Fig. 4. Appearance of adult : Dense tussock, with pale drooping foliage, and purplish flowering parts, drooping outwards. Leaf-bases pale, somewhat swollen. Dense tussock, with strawcoloured foliage, not drooping, and pale, erect flowering parts. Dense tussock, with yellowish to brownish-green, slightly drooping foliage, and strawcoloured, erect, but spread-, ing flowering parts. Small tufted plant, with short leaves > of greyish green appearance, and tall, erect flowering parts. Leaves: . . Collar: ' About 20 inches long, very narrow, rough to downward touch. With papery, rather longligule, somewhat eared. About 14 inches long, very narrow, but less so than Nassella, rough to downward touch. About 20 inches long, narrow, but less so than the two former, somewhat flattish, smooth to downward touch. About 5 inches long, narrow, rough to touch. , ' Short, finely cut at tips, Distinct, with long fine distinctly eared. hairs, distinctly eared. About 20 inches long, narrow, but less so than the two former, somewhat flattish, smooth to downward touch. Short, finely cut at tips, Reduced to narrow rim, not distinctly eared. eared. About 5 inches long, narrow, rough to downward touch. Reduced to narrow rim, not Distinct, with long fine eared. hairs, distinctly eared. Inflorescence: , . Stalk: Flowering part : Ample, spreading, drooping, the whole easily detached. About. 15 inches long, smooth. About 10 inches long, spreading and drooping. . Ample, somewhat spreading, hardly drooping, not easily detached. About 12 inches . long, rough About 6 inches long, narrow and erect. Less ample, more erect, not easily detached. - -About 15 inches long, smooth. About 6 inches -long, somewhat spreading, suberect. Ample for size of plant, erect, not easily detached. ' . . About 6 inches long, smooth. About 6 inches long, erect, not spreading. Spikelets: . . Single-flowered, purplish. Several-flowered, pale green to straw-coloured. Several-flowered, pale green to straw-coloured. Single-flowered, \ greyish to slightly purplish. ' Seeds—Base: Body: . . Bristle: . . Somewhat pointed, hairy. Short, broad, plump, ribbed, rather rough. . Flexuous, about 1 inch long, twisted below. Blunt, free from hairs. ’ Rather long, smooth, rounded on back. Very short, straight. Blunt, with cobwebby hairs. Rather long, roughish, keeled on back. Without a bristle. Sharply pointed, hairless. A Long, narrow, hairy, terete. About 2 inches long, strongly twisted below, bent at almost a right angle.

How to Distinguish Nassella Tussock