Paterson's Curse and Viper's Bugloss Control Guide

Do's and Don'ts of Paterson's curse and viper's bugloss control

Paterson's curse flowers, photo: Kiowa FennerViper's bugloss flower, photo: Kiowa Fenner


  • Plan your control program, this will save time and money in the long-run;
  • Consider the impact of your control methods on off-target species, especially if herbicides are used;
  • Ensure machinery and equipment is washed down between sites or prior to contractors leaving site;
  • Get in early - For new infestations, eradicate before the plants reach the flowering stage: once plants begin seeding, control becomes more difficult and expensive;
  • Carefully time your use of herbicide for best results (see Herbicides for Paterson's Curse and Viper's Bugloss control for more information);
  • Coordinate your control program with neighbouring landholders where your weed problem crosses property boundaries;
  • Revisit and regularly inspect the site and ensure follow-up is undertaken.


  • Don't introduce Paterson's curse or viper's bugloss to Paterson's curse/viper's bugloss-free areas (e.g. by failing to wash down machinery and equipment between sites or in contaminated seed or hay);
  • Don't start your control program without first planning your approach;
  • Don't allow Paterson's curse or viper's bugloss to flower and set seed before treatment;
  • Don't rely on one attempt at removal - follow-up is essential;
  • Don't leave flowering plants on the ground as the seed may still mature on hand-pulled, hoed or cut plants.

Spread of Paterson's curse and viper's bugloss

  • Both Paterson's curse and viper's bugloss are spread by seed. Seed can be spread after ingestion by grazing animals and birds, as well as attached to the coats of animals.
  • Seed is also spread by water and by earthmoving equipment, particularly along roadsides. Seeds are not spread by wind.
  • Seed of Paterson's curse may remain dormant in the soil for up to six years although most will germinate within two years.

Physical removal

  • Hand hoeing, pulling, and cutting can be used to remove isolated plants provided the growing tip and the top 20 to 40 cm of the tap root are removed, otherwise regrowth may occur.
  • Flowering plants should be destroyed because seed may continue to mature on hand-pulled, hoed or cut plants.


  • Both weeds can be controlled in arable areas by cultivation, especially if followed by cropping with either root or cereal crops, or establishment of a vigorous smothering pasture.


  • Heavy grazing can be used to control Paterson's curse. Sheep are the most effective grazing animals to use. Grazing should be carefully managed given the potential for Paterson's curse to cause liver damage.
  • Grazing should be concentrated when plants are young, continued at regular intervals during the year and concentrated again at the end of the year when plants are flowering.
  • Plants that escape grazing should be hand-pulled or cut to prevent seeding.
  • Viper's bugloss is less palatable and is not so effectively controlled by grazing.

Biological control

  • Biological control is the use of a living species, usually an insect, mite or disease, to control a weed;
  • The biological control agent Dialectica scarlariella was released in Tasmania but has failed to establish field populations. Other agents are available from the mainland and will be considered for release in Tasmania in the future.
  • For more information on biological control programs in Tasmania contact the Tasmanian Institute of Agriculture.

Chemical control

  • A number of herbicides are registered for use on Paterson's curse and viper's bugloss in Tasmania. (see Herbicides for Paterson's Curse and Viper's Bugloss control for more information).
  • In years when there is an early autumn break and large numbers of Paterson's curse germinate before the temperature falls, autumn spraying can be very effective.
  • The use of a wiper applicator where the Paterson's curse is reasonably uniform in size can overcome the problem of damage to desirable pasture legumes using boom spraying.
  • For effective herbicide control, plants must be growing actively. Plants subject to stress due to waterlogging, drought or low temperatures are less susceptible to herbicides.
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    To the extent permitted by law, the Tasmanian Department of Primary Industries, Parks, Water and Environment (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using information or material (in part or in whole) contained on this website.

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