Hieracium can be controlled U.S. scientist concludes

Press, 18 April 1980, Page 17

Hieracium can be controlled U.S. scientist concludes

The perennial weed, hieracium, which has infested 300,000 hectares of South Island high country and is threatening another million hectares, was able to be controlled, Mr A. Perry Plummer said recently.

■ Mr Plummer, who recently retired after working as a field scientist for the United States Forest Service for 43 years, spent last month studying the weed and deciding on the best way of combatting it. His trip here was sponsored by the. Lincoln College Foundation and the National Water and Soil Conservation Organisation, through the. Ministry of .Works and Development. Mr Plummer’s studies took him on foot, or in "the air, over many high country runs which are infested with hieracium. He also spoke with runholders and those involved in high country research. Control of hieracium could be achieved through introducing plant species which were aggressive enough to restrict and crowd out. the weed and by making changes in stock management on high country properties, he said. While he had had no experience with hieracium in Utah (although it was common in other areas, of the United States), he said that similar plants in his

home state had been restricted, then suppressed by vigorous competitive plants. To allow these newly introduced plants to survive and improve, rotational management of stock, instead of heavy mob stocking, was introduced, and blocks were sub-divided . to facilitate the introduction of rotational grazing. Mr Plummer said hieracium was causing several problems in the high country. It restricted the growth of other plants, such as tussock, so grazing ■ was restricted and the carrying capacity of the high country runs was being affected. The plant was also of concern to catchment authorities because hieracium seriously reduced the water holding capacity of soil and resulted in rivers carrying more water. There would have to be two types of cover in- ' troduced. The first would be legumes, such as lucerne, yellow sweet clpver. and mellolotus. Grasses could be mixed in with the legumes or the legumes could be planted

first to allow for nitrogen fixing. .Suitable grasses and herbs would include sheeps burnet, cocksfoot, tall oat grass, smooth brome, crested wheat grass, end hard sheep fescue. Apart from cocksfoot these grasses were not commonly available in New Zealand, so seed would have to be obtained from overseas. Several of these grasses and legumes had been tested but only on very small plots. Until the grasses had been subjected to normal grazing and weather patterns their usefulness could not be evaluated, Mr Plummer said. Grass species used for weed control work in the United States had proved successful because of growth vigour and palatihility. It was important that stock found the newly introduced grasses edible, he said. There could be a place for the sage-brush type of bush, which flourished

well in the highlands of Utah. Mr Plummer said this type of shrub would provide winter nutrition for stock and summer shelter for newly introduced grasses. The possibility of using a herbicide before planting new grasses and legumes had been examined, but it probably was not warranted, Mr Plummer said. Hieracium was not totally killed off by herbicides and so the financial cost probablv outweighed the benefit gained by a clearer seedbed. Mr Plummer said he accepted that soil would have to be prepared before seed was sown. Sowing seed and “harrowing” with large numbers of stock would not necessarily work, he said. In Utah on mountainous country land had been loosened before seed planting by using two bulldozers towing a long length of very heavy chain between them. One" machine followed a ridge-line while the other maintained a parallel course at the base of the ridge. The chain used often had links weighing 50kg and a piece ■of railway iron attached to every third link. The chain was up to 150 metres long, he said..

The disturbed soil created small areas with a micro-climate suitable for seed germination, he said. Blocks about 300 hectares in area would be about the best for management purposes. This would mean that heavier concentrations of stock could be grazed in each block and this would help in the development of any new grasses. Mr Plummer suggested that grasses on trial be sown in blocks with and without hieracium infestation. Sulpher superphosphate should be used at the time of sowing, he said.

He said the hieracium infestation could be a blessing in disguise. New Zealand had a reputation of being a world leader in pasture utilisation and observations in the more productive areas of the South Island would bear this out.

However, the high country- rangeland had been neglected to a degree but the amount of work and research going into the fight against hieracium could mean a revitalisation of the high country. New Zealand had overcome tremendous farming problems before ■ and would do so again, he said. With about 40 per cent of the high country affected to some degree by hier-* acium the time had arrived to do something about it, he said.