Nassella tussock seed ‘far from eradicated’

Press, 31 August 1989, Page 42

Nassella tussock seed ‘far from eradicated’

By

HEATHER CHALMERS

in Rangiora Fifty years ago, nassella tussock was a major threat to the productive agricultural land in North Canterbury. Large areas of dense nassella tussock covered Waipara, Waiau and, to a lesser degree, Cheviot. About 17,000 ha of land was matted with nassella tussock which had taken over pasture land.

Public concern about the problem led to the establishment of a nassella tussock committee in North Canterbury in 1941. This was followed by the passing of a Nassella Tussock Act in 1946 allowing nassella tussock boards to be established.

Only two such boards were formed in New Zealand, one in North Canterbury, covering the Amuri, Hurunui and Cheviot countires, and the other in Marlborough.

The boards will be abolished in October as a result of local body restructuring. It is one of many special purpose bodies such as pest destruction boards, noxious plants authorities and catchment boards which will disappear with their functions taken over by the new Canterbury Regional Council. Nassella tussock was introduced into New Zeland in the early 1900 s, probably as an impurity in seed imported from South America.

It is an aggressive weed with a high reproductive rate —- one mature plant is able to produce 120,000 seeds. These seeds can lie dormant in the ground for between 20 and 30 years. The nassella tussock has little nutrient value and

its fibrous leaves make it mostly unpalatable to stock.

The North Canterbury board’s operations manager, Mr Dudloy McLellan, said there was still a large store of seed in the ground in particular areas and the board was dealing with seed from plants grown from years ago.

Nassella tussock is a small plant and is only visible to people with informed eyes, Mr McLellan said.

“One of our biggest problems is convincing people that we have got it, that it’s still around.” In fact, the nassella tussock is far from eradicated and in North Canterbury, 400,000 ha still has infestations of the noxious plant. The heavy infestations of the past have gone, however, thanks to a variety of eradication methods since the board was set up. Afforestation of pinus radiata was the first method used but it was principally discontinued after 1950 because of concern over the loss of agricultural land. Herbicide was used until about 1970, to reduce dense areas of nassella tussock to a grubbable state. The main weapon than became the “old fashioned grubber,” Mr McLellan said. Hand grubbing began in earnest from 1960. It was a very labour intensive job and the board’s staff numbers rose as a result. At its peak in 1968, the board had 200 seasonal workers in grubbing gangs working nine months a year; a total of 120,000 hours.

The grubbing gangs started to decline from 1975 as farmers began to find it difficult to meet

the cost of the scheme. The board now employs only 20 people for three months of the year. The board’s permanent staff has dropped from 34 to 23 in the last three to four years.

About half the 500 properties infested with nassella tussock in North Canterbury now participate in a hand grubbing subsidy scheme. Under this scheme farmers are subsidised by the board for grubbing on their properties. Farmers still spend a total of 70,000 hours on eradication a season. “So it has turned right around from us doing the job to farmers doing the job,” Mr McLellan said. Board staff now mainly supervise the hand grubbing subsidy scheme. The board is funded by contributions from the Amuri, Cheviot and Hurunui counties, a Government subsidy and grubbing recoveries. In 1988 the board received $623,000 in Government subsidy and $66,000 from the three councils. The Government is gradually cutting back its share, contributing $296,000 this year and the counties, $lOO,OOO.

Since the board was formed it has spent $l5 million on eradication in North Canterbury. Mr McLellan said this was not a big amount considering the time since the board was established, the work it had done and the amount of agricultural land it had returned to production. It is not yet know how much funding the board will receive after restructuring but the Canterbury Regional Council was very sympathetic to its cause, he said.

“Any relaxation of control for any length of time could be disastrous. One year’s seedlings could be 10 years of problem.” The board has two members each from the Amuri and Cheviot counties, four from the Hurunui County, four from Government departments and up to three coopted members. It had attracted practical people with a lot of foresight and common sense, Mr McLellan said. One of the co-opted members is Mr Arthur Healy. When working for the Botany Division of the D.S.I.R. in 1941 Mr Healy made a survery, writing a bulletin shortly after which is still the “Bible” for the board. The board hopes that once it is dissolved, its role will be taken over by the new Hurunui District Council, an amalgamation of the three contributing county councils, although the Canterbury Regional Council will have ultimate responsibility. "It is hoped we will more or less remain intact,” Mr McLellan said.