THISTLE ERADICATION

Southland Times, Issue 23942, 7 October 1939, Page 14

THISTLE ERADICATION

In the lower rainfall areas Scotch thistles occur only on the best lands, where they appear to be easily controlled. In the higher rainfall areas, however, where heavy top-dressing is practised, Scotch thistles are a very persistent weed in the better pastures. If allowed to mature and seed, they ruin the sward. To control this pest many methods are used, with varying degrees of success. The practice of shearing off the leaves of rosette plants at ground level with an adze or spade will check the plant for a short period. However, this merely aggravates the position, as the plant usually regenerates from the roots and forms a multiple-crowned thistle, which ruins a greater area of pasture than the undisturbed plant. Another practice which aims at the destruction of seed is the practice of mowing the thistles after the seed stalks have grown, all seed stalks and seed being collected and burned. Although the thistles will again produce fresh stalks, they also can be destroyed and a large amount of reseeding prevented. A satisfactory method or eradication is either to spray with a 5 per cent, solution of sodium chlorate or to dust with a 5 per cent, mixture of sodium chlorate and lime while the plants are in the rosette stage. Although this treatment leaves a bare patch in the pasture for some time, it usually kills the plant and prevents the formation of seed. After a while the toxic effect of the poison disappears. Pastures then revive, and fill up the bare patches.