CALIFORNIAN THISTLE

Press, Volume XCIV, Issue 28104, 20 October 1956, Page 9

CALIFORNIAN THISTLE

RECOMMENDATIONS BY DEPARTMENT

Californian thistle if unchecked can become a serious problem both in pastures and crops. In pastures large areas of thistle take up much grazing land and in crops the yield can be greatly reduced.

With heavy infestations in either pastures or crops the most satisfactory method of control, says the Department of Agriculture, is with hormone weedkillers. Because of the thistle's strong underground root system control by cultivation can be protracted, with a limited chance of complete success.

Better control is obtained from the salts and amines of MCP than from the equivalent 2.4-D compounds. Areas with strongly established thistles require more than one application and should be sprayed- with 111 b acid equivalent an acre of MCP at flower set. If the weed is mown and treated in autumn at the rosette stage, lib acid equivalent an acre of MCP salts gives effective control.

Where pasture is run out best control is obtained by ploughing and discing and then sowing a crop, such as potatoes or a cereal, which is not damaged by MCP sprays. Thistles appearing in the crop can then be sprayed with lib acid equivalent of MCP. Since cultivation will break up the roots of thistles and stimulate growth, all the thistles will not be killed. However, those that come up when the area is resown to pasture can be controlled by MCP.