SWEET BRIER CONTROL

Press, Volume XCVIII, Issue 28920, 13 June 1959, Page 9

SWEET BRIER CONTROL

Better Method Needed

The problem involved in sweet brier control experiments was to find a method of eradication which was easy to apply, was economical in cost and gave satisfactory results, the fields superintendent of the Department of Agriculture in Christchurch (Mr A. R. Dingwall) said last week. To date, no sufficiently efficient chemical had been available which would provide a satisfactory method of eradication in practice.

Several chemicals will kill sweet brier readily, but the difficulty lies in the problem of practical application. Under the conditions where sweet brier normally occurs it is almost impossible to apply chemicals efficiently on large infestations.

“We’ve been looking for a number of years for a chemical which could be applied from the air and which would kill the plant, and at the same time would not be too costly,” he said. “The chemical, 2,4,5,T doesn’t translocate readily in the plant. “Good penetration is achieved, but the chemical doesn’t move from the point of entry throughout the stem, leaf and root system. Until a chemical is found which wilj do this in woody plants it will be hard to treat and kill sweet brier.’’

The plant has a strong rooting system and suckers are thrown up readily, he said. Where bushes are in the nature of a thicket they are generally the result of suckering and killing out the top growth with covering sprays was followed by suckers coming up all over the place. Basal application of chemicals to thickets was impracticable.

Isolated bushes could be treated by basal application very efficiently, Mr Dingwall said. An oil concentrate of 2,4,5 T in diesoline at a ratio of one to 88 was sprayed to the crown and bottom 12 inches of canes and to a 15 inch • radius of the ground surrounding the crown.

W’ith covering sprays 2.4.5 T could control top growth and seeding, but even if the treatment was repeated up to three times it was not likely to result in a reliable kill because of the crown regrowth and suckering from the roots, which might well run for up to 12 feet from the crown.

Apart from the hormone sprays one or two of the urea compounds were being investigated. These were of the soil sterilant type and, while being very expensive, were very efficient for basal application. Pellets containing up to 25 per cent, by weight of the urea compounds were bein«' tried, he said.

Apart from the high cost, the urea compound killed most of the vegetation and left “bare earth” for possibly as long as six months, which could well be a hazard in erosion prone areas. Recent trials using 2,3,6T8A, a benzoic acid derivative, had proved quite effective,, both as basal and covering sprays, in controlling top growth and by this spring some indication of their effect on crown and root growth would be known. . *?.!? easy ’ and relatively cheap, to kill off and remove the' top growth, control regrowth by spraying in the autumn and then graze with sheep throughout the winter and thus kill sweet brier but as a practical method it has many obvious drawbacks. It- is not the farmer’s answer.” A method of easy application, economical and giving results was looked for and the department was persisting with its trials work Several new chemicals were to be tried this next year, Mr Dingwall said. &