Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Effect of wounding followed by intensive grazing on Californian thistle control.

Abstract

Field studies were conducted at 6 sites in Otago, New Zealand, during December 1992 to February 1993 to study the effect of a 'clod crusher' to wound the stems of Californian thistle (Cirsium arvense) in pastures prior to intensive grazing by sheep. Sheep in the trial area were observed to preferentially graze wounded thistles in favour of untreated thistles within 48 h of treatment, indicating that wounding increased the palatability of thistles. Although thistles recovered soon after treatment, regeneration apparently weakened the plant as shown by the reduced number of thistles present (30-47% for the December treatment) in the following summer. It was concluded that this technique gives a low-cost method of giving an immediate reduction in thistle densities in early summer when ewes are available after weaning to provide the grazing pressure required.