NASSELLA TUSSOCK IN SOUTH ISLAND

Dominion, Volume 35, Issue 290, 5 September 1942, Page 4

NASSELLA TUSSOCK IN SOUTH ISLAND

Threat To Pastures

Investigations which it is hoped may bring results of considerable importance to farmers of North Canterbury and Marlborough are at present being carried out by the Botany Division of the Department of Scientific and Industrial Research. Research workers are studying tlie life history of the South American tussock, nassella, to find out whether the plant has a weak spot which may enable it to be easily destroyed. How nassella was brought to New Zealand is not known, but it has been present in the South Island for at least 40 years. Spreading at a rapidly increasing rn’tc, it has. in recent years, seriously curtailed production on. large areas of laud 'in North Canterbury and Marlborough. Alarmed at the growing menace, farmers in 1939 appealed to the Government for help. A preliminary- survey of the incidence of the pest was imide in that year by the director of the Botany Division. Bast year a detailed investigation was undertaken, an oflicer of the Botany Division and one of the Department of Agriculture spending three months on the work.

They found that the pest was present on 82,<100 acres in North Canterbury and that another 252,000 acres were threat* ened with immediate infestation by wiudborue seed. In Marlborough it was found that 5000 acres were affected, 300 seriously. „ , Threat to Pasture.

Nassella is a dense tussock, growing about two feet high. The leaves are narrow and coarse, with minute bristles. The heads, carrying the seeds, .emerge on long, trailing stems, which are readily detached and distributed by the wind. At flowering time, early in December, large blocks of tussock give the appearance of a purplish haze over the ground. Unlike the native tussock, which gives valuable shelter to pasture growth, nassella ultimately crowds out all other vegetation on infested areas. 'the herbage is useless as stock teed. .Hie beads are carried by the wiud for miles and in huge quantities. They are often seen piled up live or six feet high against trees or fences. As a result, clean land can quickly become infested. The tussock' is not susceptible to ordinary weed-killers. Farmers are adopting the expedient of burning about seed time, but, though this temporarily prw vents the spread of the pest, established plants are not. destroyed. In one case, in a drought period, growth of half an inch a day wns observed after burning. Another disadvantage is that the burn opens UP the ground cover mid allows closer establishment. Grubbing has been found the only really practicable method of dealing with the pest, but. of course, it is economic only on small areas. Investigations made recently by an officer of tlio division show Hint the tussock has spread to new arcus in the last vear and laboratory and held work by the Botany Division is directed toward "•ainiii" a fuller knowledge of (he lite history of the plant, ’an essential step toward finding measures for control.