grass roots community organisation that aims to improve natural condition of the derwent catchment

Slender Thistle and Winged Slender Thistle

Disclaimer

The following page is a brief summary of information available on the DPIPWE website regarding Slender Thistle control. For more information view here

Non-chemical control

Physical removal

  • Slender Thistles are not generally killed by cutting or slashing as cut plants are likely to regrow.
  • However, cutting or slashing when plants are in late bud or early flower (late spring to early summer) can reduce the amount of seed.
  • Cutting and slashing should not be left too late as seed can mature on cut plants lying on the ground. If the plant is in full flower, heads should be collected and burnt to destroy the seed.

Cultivation

  • The best way to control Slender Thistle is by encouraging competition from useful plants such as pasture. Vigorous pasture minimises Slender Thistle establishment and growth.
  • Patches of bare ground (for example, from rabbits, overgrazing, insect attack) can lead to an invasion by Slender Thistles. Patches of bare ground should be revegetated, preferably by insect resistant grasses such as Phalaris or Cocksfoot.
  • In areas which are heavily infested, growing a cereal crop for one or two seasons can reduce the thistle population, provided a suitable herbicide program is used (see Herbicides for Slender Thistle Control for more information).

Grazing

  • Goats will graze Slender Thistles. Over a period of several seasons goats prevent seed production and can produce a reduction in Thistle numbers.
  • Slender Thistles are not normally grazed by cattle or sheep. However, where thistle germination occurs mainly in the autumn, deferred grazing can be an effective control measure in established perennial ryegrass pastures.
  • Deferred grazing involves the closing off of an infested area to grazing in the autumn before the first Thistle seedlings emerge. The grass is then allowed to grow to at least 15 cm. Competition with the grass during the early stages of Thistle growth forces the Thistles to elongate prematurely and produce soft and palatable plants instead of the usual hard prickly rosette. The area is then heavily grazed with sheep using at least twice the normal stocking rate.

Biological control

  • Several strains of Slender Thistle rust fungus have been introduced to Tasmania to help control Slender Thistles. The rust works by infecting the leaves and flowering stems which weakens the plant, making the Thistles more susceptible to competition from desirable pasture species.
  • Biological control will not eradicate Slender Thistles, but can be used in conjunction with other control methods as part of an integrated management program.
    For more information on biological control programs in Tasmania contact the Tasmanian Institute of Agriculture.

Chemical control

Use herbicides in accordance with label. Refer to APVMA permit PER13160 where herbicide is to be used in non-cropping and bushland areas

Application method

1. Boom spraying

  • Stage of growth (a) - Seedling-young rosette
  • Location - Pasture and non-cropping
  • Suggested herbicide - Kamba®M
  • Stage of growth (b) - Rosette prior to flowering (prior to stem elongation)
  • Location - Non-legume pasture
  • Suggested herbicide - Lontrel®750 SG

 

2. Spot spraying

  • Stage of growth - Seedling-young rosette
  • Location - Pasture and non-cropping
  • Suggested herbicide - Kamba®M