Saffron Thistle Control Guide

Spread of saffron thistle

Saffron thistle flowering spring

  • Saffron thistle is spread by seed.
  • Saffron thistle seed is not readily moved by wind, and most seed falls directly below the parent plant. As a result infestations tend to persist in the same area and spread is not rapid.
  • Sheep may eat the seeds and pass them through the digestive system, assisting the weed's spread throughout a property.
  • Seeds may also spread in the fleece and coats of livestock, through soil movement on equipment and machinery, and through water movement along drainage lines.
  • Saffron thistle seed remains dormant in the soil for at least eight years. Seed buried more than 10 mm deep may remain dormant until cultivation or other soil disturbances bring it to the surface.


Avoid the introduction of saffron thistle

  • Avoid introducing seed into clean areas, or into areas from which the weed is being eradicated.
  • Implements which have been used on infested areas should be thoroughly cleaned on leaving.
  • All feed grain or hay should be free of saffron thistle seed.
  • Any livestock suspected of carrying seed on their bodies or in their digestive system should be held in a suitable area for approximately two weeks before being put on clean paddocks.
  • Special care should be exercised when buying sheep from other properties as seed is readily carried in wool.
  • See the Washdown Guidelines for Weed and Disease Control for detailed information on how to wash-down equipment and personnel to reduce the chance of spreading


Physical removal

  • Grubbing can be used to remove saffron thistle where the number of plants involved is small.
  • Plants should be collected and burnt.
  • Slashing or cutting can be used to reduce maturing saffron thistle, but must be undertaken at the correct time.
  • If plants are cut before the stem is fully developed, plants may regrow; if plants are cut after flowering has begun, viable seed may still be produced on the cut stem.
  • The optimum time for slashing or cutting usually occurs around October to November.


Cultivation

  • Most saffron thistle infestations in Tasmania are relatively small and occur in low rainfall, stony areas, making control by cultivation difficult.
  • Where cultivation is possible, a three years' program of establishing a competitive pasture or crop (wheat or barley) can induce germination and exhaust the reserve of thistle seed in the soil.
  • Any thistles which survive the cultivations should be sprayed with herbicide in the crop.


Chemical control

  • A number of herbicides are registered for use on saffron thistle in Tasmania. See Herbicides for Saffron Thistle Control for more information.
  • Saffron thistle can germinate from autumn through to late spring, and it may be advisable to delay spraying until late in the season to ensure all plants are found and treated, particularly for scattered and sparse infestations.


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