WEED KILLING TRIALS

Bay of Plenty Beacon, Volume 10, Issue 95, 17 February 1947, Page 7

WEED KILLING TRIALS

DOMINION PROGRAMME CAUTION URGED IN ASSESSING VALUE As part of a Dominion programme of investigation, substantial supplies of substances for use in weed control trials in Canterbury, Marlboor ugh, Nelson and Westland have been received at Christchurch by the Department of Agriculture. The substances include some of what are considered to be the most promising new products of British and American laboratories, reported the District Field Superintendent (Mr R. P. Connell) recently. After making some cautionary remarks on assessing the value of hormone weed killers, Mr Connell said the present indications, especially from overseas, suggested that they would be of value in killing some weeds which were troublesome to farmers, as well as for weed control in lawns and greens.

Certain of the substances reflected a new approach to weed control in which many farmers had become interested on account mainly of overseas reports which had'' been given publicity, said Mr Connell. The weed killing, or herbicidal, properties of such substances were variously attributed to “hormone,” growth controlling, or “growth regulating” materials. They wefe known under a range of proprietary names among which Weedone and Methoxone were becoming familiar.

“The proposed field trials will cover all the main weeds,” he said. ’’For instance, they will embrace not only annuals and perennials which worry the farmers on the plans, but also such weeds as sweet briar and St. Johns wort, which are of more concern to the hill country landholder. Already some preliminary work has been done; that by the Department of Agriculture has been mainly at the newly established Soil Fertility Research Station at Hamilton depot.

The preliminary work had been insufficient to provide a basis for definite recommendations above the

practical use and value of the materials under trial, but the work had shown that, under specific conditions, some plants were more susceptible to damage than others. For instance, clovers had been damaged more readily than gorse. There was also some evidence that the effects of the hormone type of weed killers varied with the growth activties of the plants and • with differences in temperatures and in soils. It had been stated that the hormone type of weed killer left a residual effect harmful to susceptible plants which followed and that the length of this harmful effect depended on the concentration of the weed killer applied and may be also on the type of soil.

“That the hormone type of weed killer has generally a practical value under New Zealand conditions should not be accepted too readily,” said Mr Connell. “Despite the favourable notice they have received in some of the popular scientific type of publications, the scope for their economic use under New Zealand conditions may be quite limited and judgment on this should be deferred pending the results of critical conclusive experiments. A point to this remark is given by the fact that the following so far have been classed tentatively as “resistent” to hormone weed killers: Blackberry, bracken, fern, Californian thistle, ragwort, yarrow, sorrel, black nightshade and willow weed. On the other hand among the weeds classed tentatively as “susceptible” to these substances are sow thistle, Scotch thistle, dandelion, hawkbit, nettles, plaintains, fathen, cornbind and penny cress.”