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  Services » Regional Services » Plant and animal pests » Pest plants » Ragwort

Ragwort

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Ragwort
Jacobaea vulgaris (formerly known as Senecio jacobaea)

Sustained control
Keep ragwort from affecting nearby land.

Why it is a pest plant

Sustained control
Keep ragwort from affecting nearby land.

Production threat Environmental threat Public threat

Identifying features

Ragwort is an agricultural pest in the Waikato. It is a highly invasive pest plant which has unpalatable foliage, reducing pasture production throughout New Zealand. It is also found in waste places, riparian margins, open forest and swamps. Ragwort reproduces from crowns, roots and wind-borne seeds. Ragwort is more apparent on dairying and drystock properties and if eaten, its foliage is poisonous to cattle and horses.

Responsibility for control

All landowners/occupiers in the Waikato are responsible for controlling ragwort on their properties and are required to work with Waikato Regional Council in areas where control programmes are in place. If you graze the roadside then you are responsible for controlling this plant pest on that adjoining land. The level of control depends on where the property is.

  • On properties in ‘total control’ areas, all ragwort must be controlled.
  • On properties in ‘boundary control’ areas, all ragwort within 50m of the property’s boundaries must be controlled on complaint from an adjoining neighbour.

See the map below for an overview of the locations of the two types of control zone.

Ragwort is also banned from being sold, propagated, distributed or included in commercial displays.

How to control ragwort

Some options for managing ragwort are included in this factsheet, but there are others. For more information contact your herbicide representative or check www.pestweb.co.nz.

Physical control

Pulling plants out and disposing of them by deeply burying, burning or composting (if no seed heads are present) is an effective method of controlling ragwort. Plants are best pulled at the flowering stage where the roots are much less likely to regrow. Mowing ragwort is not recommended, as it will encourage the plant to become multi-crowned or to become a perennial plant, making it difficult to control. Ragwort is poisonous to cattle and horses but not sheep, so stocking ragwort-infested areas with sheep will reduce the number of plants.

Grazing management

Ragwort can be grazed by sheep or goats. However, cattle rarely eat ragwort seedlings or rosettes.

  • Damage to pasture cover or soil disturbance increases ragwort seed germination.
  • Continuous grazing, as opposed to rotational grazing, is more likely to lead to ragwort infestations. Under continuous stocking livestock can graze selectively, which can lead to overgrazing and ragwort establishment.
  • Once the seedling has formed a rosette, it competes well with grasses and clovers. At this stage, only tall pastures such as a hay crop may reduce its growth.

Pasture species/cultivars

  • Maintaining a dense, vigorous pasture can help prevent ragwort germination and establishment.
  • This can be helped by appropriate stocking rates, irrigation and fertiliser.
  • Superphosphate and urea applications have both been shown to increase pasture growth and suppress ragwort.

Mowing or grubbing

  • Small patches of plants can be removed by hand or grubbing. However, plants can regrow from root fragments left in the ground.
  • Pulled plants should be removed and burned so viable seed does not spread.
  • Larger plants have deep root systems, making it hard to remove all the roots. However, as plants get older, regrowth from root segments is less likely.
  • If plants are mown, they can regrow and produce multi-crowned plants, each crown with stems. This may prolong the life of the plant and turn it from a biennial to a perennial.
  • Mowing or cutting repeatedly, in combination with appropriate fertilisers, can favour grass growth and help prevent ragwort from establishing.

Ploughing

  • For large infestations, deep ploughing followed by summer and autumn cultivations can kill ragwort plants, regrowth and seedlings.

Integrated pest management

  • Older plants may be hard to kill. However, one technique is to leave them to die naturally in ungrazed areas, followed by grazing, spot-spraying and maintaining a dense pasture to control the seedlings.

Herbicide control

There are many herbicides that will control ragwort. The herbicide best suited to your property will depend on the level of infestation, the application equipment you have available and the stage of growth the plants are at. Some suggested herbicides are included in the table in this factsheet. Contact your local biosecurity pest plant officer for free advice on what herbicide and application method would best suit your situation on freephone 0800 BIOSEC (0800 246 732).

Spray application

A boom/aerial application of herbicide will affect desirable species such as clover and ryegrass. This damage can be minimised by applying herbicide to ragwort plants in the seedling/rosette stage during autumn and early winter. Be aware that ragwort plants may become more palatable to cattle and horses after spraying. Stock should be removed until the treated plants die.

Small block owners who may not have access to spray equipment could consider physical control methods (see above) or select a herbicide such as picloram granules. Picloram is a dry application powder which does not require mixing or spray equipment.

Herbicide control tips

  • Young plants in the rosette stage are easier to control than older plants.
  • 2,4-D is more effective on younger than older plants (including older rosettes, budding or flowering plants).
  • 2,4-D and MCPA damage clover. Some products used to control ragwort also damage grasses.
  • Check regarding withholding periods for the chemicals used. There may be a withholding period of up to several weeks before stock are allowed back onto the pasture.

Safety when using herbicides

  • Follow the instructions on the manufacturer’s label.
  • Always wear protective clothing.
  • Always minimise the risk to your other plants.
  • Contact the supplier for further advice.
  • Consult your farm consultant, industry rep or New Zealand Novachem Agrichemical Manual for more information about chemical control.

Identifying features

A biennial or perennial daisy, ragwort grows to between 45-60cm high. It has masses of yellow flowers. However, recognising the juvenile plant is more difficult as the leaves look quite different once the plant has matured. Plants have an unpleasant smell when crushed.

Flower

  • Bright yellow flowers, each about 2cm across.
  • Flowers are in flat-topped clusters.
  • Flower stems can grow up to 1.2m tall.
  • Flowering is from November to April.

Fruit/seed

  • Parachute-like light-coloured seeds attached to fine hairs.
  • The fine hairs open out to form a fluffy ball (thistledown).
  • The fluff helps the wind to spread the seed more widely.

Leaf

  • As a young plant, ragwort is a flat rosette of dark green leaves with large lobes.
  • As the plant matures and forms a stem, the leaves become deeply cut and stalkless, growing close to the stem.

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Disclaimer: Any product names mentioned below are not an endorsement nor are they a criticism of similar products not mentioned.

Summary of herbicides and application methods for control

Active ingredient

When to apply

Residual effect

Grass damage

Clover damage


 2,4-D   Up to small rosette  Slight   No  Slight
Dicamba Up to large rosette Severe  No Severe
Triclopyr/picloram Up to large rosette Yes  No Severe
Metsulfuron-methyl Up to large rosette Yes Moderate Severe
Picloram Up to large rosette Yes  No Severe
MCPA Up to small rosette Moderate  No Slight
 Glyphosate  Any stage No Severe Severe
Aminopyralid Up to large rosette Severe  No Severe
Clopyralid Up to large rosette Severe  No Moderate-severe
Thifensulfuronmethyl Up to small rosette Slight Slight Moderate
Mecoprop/dichloroprop/MCPA Up to small rosette Yes  No Severe
Herbicide rules will apply. You may need to notify neighbours if spraying. The Waikato Regional Plan explains the agrichemical (herbicides) use rule in section 6.2

 

Biological control

Biological control involves importing insects or fungi that feed on plants in their native countries. Biological control agents reduce infestations but do not eradicate plants from an area. All the following biocontrol agents have been released throughout the Waikato and have established themselves in all suitable areas. If you have ragwort on your property you will still need to undertake control work.

Biocontrol agents released in the Waikato to attack ragwort include:

  • cinnabar moth
  • ragwort flea beetle
  • ragwort plume moth.

The ragwort flea beetle has had the most significant impact on ragwort in the region. In its larvae stage, the beetle feeds on the crown of the ragwort plant. Ragwort flea beetle was released in New Zealand in 1981 and has in places reduced ragwort from 60-98 per cent of its former density.

Landcare Research runs a national biological control programme. Waikato Regional Council supports the programme and maintains a local biological control programme for the Waikato region.

More information

Advice

  • For advice and additional information on control methods, call our pest plant staff on freephone 0800 BIOSEC (0800 246 732).
  • Chemical company representatives, farm supply stores and garden centres can also be good sources for advice.

Publications

View, download or order the following publications or call our freephone 0800 800 401.

  • National Pest Plant Accord (Manual of plants banned from sale, propagation and distribution) ($10.00 plus GST)
  • Plant Me Instead! (Plants to use in place of common pest plants) (free)
  • Waikato Regional Pest Management Plan (RPMP) (free) (Section 5.69, page 163)
  • Waikato Regional Council pest guide (free)
  • What makes a pest a pest? A summary of the Waikato Regional Pest Management Plan (free)

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