Control
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.
Chemical control
- 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
- Chemicals that can be used include: 2,4-D, dicamba, triclopyr/picloram, metsulfuron, picloram, MCPA and glyphosate.
ALWAYS READ PRODUCT LABELS BEFORE APPLYING
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 |
thifensulfuron-methyl |
Up to small rosette |
Slight |
Slight |
Moderate |
mecoprop/dichloroprop/MCPA |
Up to small rosette |
Yes |
No |
Severe |
Consult your farm consultant, industry rep or New Zealand Agrichemical Manual for more information about chemical control.
Mowing or grubbing
- Small patches of plants can be removed by hand or grubbing. However, plants can re-grow 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, re-growth from root segments is less likely
- If plants are mown, they can re-grow 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, re-growth 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.
Biocontrol
- In recent years the combined effects of biocontrol agents have significantly reduced the incidence of ragwort in most areas.
Cinnabar moth (Tyria jacobaeae)
- Cinnabar moths were first established in New Zealand in the 1939s, but only became well established in the southern North Island. In the 1980s moths from there were multiplied and released throughout the country
- Cinnabar moths have now established throughout the country but distribution is patchy. However, populations seem to be growing
- Moths are about 2 cm long with red and brownish-black markings. Cinnabar moth caterpillars vary in the damage they cause to ragwort plants, sometimes being severe in their effects and sometimes less so. They become brightly coloured as they get older, with smooth, bold, yellow-and-black stripes.
Ragwort flea beetle (Longitarsus jacobaeae)
- Ragwort flea beetle was first released in the late 1980s and early 1990s, is now well-established throughout the country and has contributed strongly to the decline of ragwort in New Zealand
- Small (2.5–3.8 mm long) golden-brown adults have large hind legs that allow them, when disturbed, to leap 1 m. Larvae are white and feed on the roots, inside the crown, and within the leaf petioles
- Heavily-infested plants die and, if plants survive they produce fewer flower stems
- The cinnabar moth and the ragwort flea beetle are complementary: cinnabar moth larvae feed on ragwort flowers and leaves in summer and flea larvae feed on the roots, crown and leaf stalks during the rest of the year.
Other biocontrol agents
- Ragwort seedfly (Botanophila jacobaeae) was released in the late 1930s, but only established in the Central North Island and has not spread further. The adults are small grey flies and the white larvae feed inside the flower heads, reducing seed production in early flowers but their impact is less later in the season
- Ragwort stem and crown boring moth (Cochylis atricapitana) was introduced to the West Coast from Australia in 2005 because other agents seemed not so effective there. Caterpillars mine into the leaves and then into the stem, causing stems to thicken and leaves to bunch up. It has not yet established, so as yet it has had no effects
- Similarly, ragwort plume moth (Platyptilia isodactyla) was introduced to the West Coast in 2005. Again it is too soon to see any effects on ragwort populations.