EXTERMINATION OF WEEDS

Nelson Evening Mail, Volume LXIV, 29 May 1930, Page 5

EXTERMINATION OF WEEDS

VALUE OF SODIUM CHLORATE _ln view of experiments being carried out by the Fields Division of the Department of Agriculture in connection with the destruction of weeds by means of sodium chlorate and calcium chlorate ; a representative of "The Press" interviewed Mr R. McGillivray, Fields Superintendent of the Christchurch office, regarding the results of experiments to date. Mr McGillivray said that, in the case of many weeds, experiments wrth the spray, without fear of contradiction, had been absolutely effective. He said that various sprays had; been experimented with for years, but sodium chlorate and calcium . chlorate were easily the best things, tried.

WEEDS KILLED Weeds like ragwort, St. John's wort, ox-eye daisy, and similar soft-leaved weeds were completely killed .where proper spraying was done. Nothing in the nature of a deluge of spray was required, all that was necessary being a light wetting of the plants. The materials were tried out at various strengths from one to ten per cent., and it was found that sprays of four to five per cent, gave excellent results, and even sprays of two and a half per cent, had been effective. The general advice, however, was to use a spray between three and five per cent, according to the age of weeds. In the case of plants with matured growth the five per cent, was recommended. .Spraying should not be done in the rain, but in cases wnere spraying was carried out, and rain set in a few hours later, the rain did not seem to have any detrimental effect on results. ■Spraying with up to five per cent, strength had no effect on grass, but stronger solutions caused considerable burning.

NON-POISONOUS MIXTURE It was of special interest and importance that sodium chlorate and calcium chlorate were non-poisonous, and spraying could be carried out at any time without removing 'grazing stock. It was said that sodium chlorate was easily inflammable when drying on clothing, and precautions therefore should be taken to wash clothes which had been saturated with that spray. Calcium chlorate was not inflammable. It had been found that w'nere considerable work had been carried out in a strong growth l of weeds ; it was not completely effective, owing to some having been missed. In all such cases farmers were advised to go over the area and attend to the weeds missed.

Any kind of spray pump could be used according to the area to be treated, but the knapsack sprayer had been found to be very effective. The Nozzle should be fine, so that plants were treated without undue expenditure.

THE COST Many enquiries had been received in connection with the cost of carrying out the spraying. It was difficult to arrive at the quantity of material required to spray an acre of weed-infest-ed land. At the Stratford Demonstration Farm in cases where ragwort was scattered over the area, Ijdb of material was used per acre in three sprayings.

On another farm where a solid block of five acres of ragwort three feet high was treated it took 231 b per acre to carry out the work. In that case, although most of the plants were in bloom, the effect was such that no seed ripened, and the spray proved completely effective. Mr McGillivray further stated that the general question of the cost of sodium chlorate and calcium chlorate was at present receiving attention, and the indication was that sodium chlorate would cost 4s 4d to 4s 6d per lb. At present there was no indication as to the probable cost of calcium chlorate, but it was expected to be about the same as the other material.

Lincoln College has also experimented successfully with sodium chlorate.