Views Differ On Nassella Control On Wrekin

Press, Volume XCVI, Issue 28448, 30 November 1957, Page 6

Views Differ On Nassella Control On Wrekin

At the last meeting of the North Canterbury Nassella Tussock Board, Mr D. R. Wilkie gave an optimistic view of work being done to control nassella tussock on the Wrekin in Marlborough, and said that the board would gain confidence in its approach to the tussock if it saw what was being done there. He described it as an "eye-opener.” On Thursday Mr J. W. Earl, who with three other board members, inspected the Wrekin last month, said that on an area of 60 acres oversown in March last year after spraying of the tussock for a kill, there was still evidence of seedling tussock coming, although already between £8 and £9 an acre had been spent on grubbing since oversowing. Mr Earl said that when he inspected the area in May this year as a member of a committee of the board which had the task of preparing a report with recommendations for control of the tussock in North Canterbury, oversowing on the 60-acre block appeared at that time to be a success. The drier facings stood out as a mass of green, which appeared to consist mainly of subterranean and white clover, and was dense enough at that stage to tend to prevent seed strike of, the nassella. In the spring of last year seed control of nassella by grubbing had cost £2 5s an acre. Opening Up Last month this block still showed up as a green mass compared with the surrounding hills, but closer inspection revealed a definite opening up of the introduced sward in the drier positions. On these drier areas there was evidence of recent grubbing, mainly of seedling tussocks, which had cost the Marlborough Board more than £6 an acre, making a total cost since oversowing in March last year of between £8 and £9 an acre.

"In view of Mr Wilkie’s statement I, for one, was surprised to see on the drier portions of this block a general showing of growing seedling tussocks, some of which if left could perhaps produce seed this coming autumn. “The fact that on this block more than £8 an acre has had to be spent on grubbing, and there is now definite evidence that further expenditure will be necessary in the near future gives me disturbing thoughts about what

will be the position this board will find itself in should it embark on large-scale use of T.C.A. and dalapon for a kill of existing tussock and oversowing, as planned, with the apparent need for follow-up grubbing as has been the experience of the Marlborough board.” Competitive cover was an essential factor on country subject to infestation to mitigate the inroads of the tussock, but it still had to be proved that this cover could be held economically on unploughable north-west facings in North Canterbury. Fertility Factor

Mr Earl suggested that a factor in the heavy establishment of clover on the 60 acres at the Wrekin was the extra fertility derived from the concentrated stocking of cattle during the nassella seeding control period. If this effect was real, then it would not be duplicated in North Canterbury except on a small portion of Glenbourne. As far as spraying and oversowing being a cure for heavilyinfested areas, the results to date pointed to dormant seed being a nuisance element which would assume greater proportions as the competitive cover weakened. It was apparent that this was already happening on the Wrekin block.

“To say that the grasses can be re-established after further spraying of the tussock for a kill is probably correct, but is the cost and labour necessary to prevent seeding on ail heavily-infest-ed areas so treated a practical proposition?” he asked. “The point is that this oversowing experiment is still in its early stages, and the true position will not be able to be assessed for some years," he said.