HORMONE WEED KILLER

Press, Volume LXXXIV, Issue 25677, 14 December 1948, Page 7

HORMONE WEED KILLER

CATCHMENT BOARD’S EXPERIMENTS “SPECTACULAR RESULTS” From Our Own Reporter TIMARU, December 13. The efforts of the South Canterbury Catchment Board to eradicate willow, broom, and lupin growth in rivers in South and Mid-Canterbury by spraying with a new hormone weed killer in the sase of light growth, and “frilling” or injecting the killer into cuts in larger trees, are being watched with interest by local bodies and similar authorities throughout New Zealand. While experiments are being carried out elsewhere, the South Canterbury board is the first to undertake large scale operations. In an address to the board the board’s engineer for the central division (Mr A. H. Mawson) showed with specimens of treated growth, that the work has every likelihood of producing spectacular results. Experiments in willow poisoning were commenced in South Canterbury in November, 1947, said Mr Mawson, when it was known that finance would be made available for willow clearing. Now the board had about 120 experimental plots, which were under constant observation. In addition to hormone killers, arsenical compounds were also tested in the original experiments, but so promising were the hormones that the latter group was dropped. With additional finance available at the end of last January, killing was started on a large scale. These operations consisted of “frilling,” which was carried out on trees of more than five inches in diameter. A circular cut was made in the back of the tree, just sufficient to reach the filmy layer that carries the sap, and into this was squirted the poison with a loose" nozzle knapsack spray. Early in April it was thought advisable to halt this work. Results of “Frilling” Questioned as to the results, Mr Mawson said that within a month or two a small percentage of the trees were dead, but the majority simply changed leaf colour much earlier, although they did not lose their leaves until the normal autumn leaf fall. They came out into* full leaf in the spring, at the same time, as other trees, but since then many had already lost their leaves and were definitely dead or dying. The roots of these trees were found to contain poison. This was important as dead roots would not bind the shingle and prevent the river from scouring out its course, he said. Recent “frilling” was attended by spectacular results, indicating that warm summer conditions were ideal for the operations, said- the board's chief engineer (Mr W. E. Lucy). Within a fortnight, even 70 feet high trees were found to have every leaf browned off and within six weeks to two months the timber dried out.

Large Scale Spraying Only with the purchase of modern pump spray equipment, pulled by a half track tractor, about two months ago, was it possible to undertake large scale spraying. The equipment had a 400-gallon tank from which spray was squirted over a wide area at a pressure of 6001 b to the square inch. Used against light, thin growth, the spray operation appeared to be extremely economical. Since large scale spraying began the bark of willows so treated had taken on a scabbiness and changed colour. The spray consisted of a mixture of hormone killer and water in the proportion of about one gallon to 'three gallons of hormone, depending on the type of growth, in a mixture of 100 gallons of water and hormone. The spray had the advantage of being harmless to stock, fish or domestic water supply. An interesting aspect of the hormone killer was that in America it was found to boost growth, when applied at a certain strength, he said. w Windrowed and Burnt When the growth is dead it is bulldozed into windrows and eventually burned when dry. At present 43 miles of the Ashburton river is being poisoned at an estimated cost of £4OOO. Eighteen miles of the Hinds has been completed. The Orari, Temuka, Waihi and Opihi rivers have also been treated. The results of some of the work can be seen from the State highway bridge over the Temuka river, towards the railway bridge. Excellent results have also been obtained against broom, up to a 60 per cent, kill with the first spray, and also with lupin, even in winter time. When dead this type of growth is burnt 3s it stands. “Although the results have been most satisfactory to date, even spectacular, it is too early yet to come to definite conclusions in the matter.” says the annual report of the catchment board.