Madagascar ragwort

Scientific name: Senecio madagascariensis Poir.
  • Key characteristics
  • Biology
  • Impacts
  • Control
  • Further information

Key characteristics

  • Annual to perennial depending on environmental favourability and management.
  • Multiple stemmed with fibrous roots.
  • Small yellow flowerheads that flower throughout the year.
  • Seed is wind-dispersed with some travelling long distances, though most seed falls within a few metres.
  • Leaves are variable in size and shape but usually narrow and lanceolate.
  • Difficult to control as it gets larger and develops a woody stem.
  • The whole plant is toxic, with a similar range of pyrrolizidine alkaloids to common ragwort. They are more toxic to cattle and horses than sheep and goats.

 

Origin

  • Native to southern Africa including Madagascar and South Africa.
  • Spread across the world to Australia, Hawai’i’, Japan and parts of South America.
  • Populations in Northland were first correctly identified as Madagascar ragwort in 2022 but were known to be a problem for local farmers for decades, who referred to it as ‘gravel groundsel’ (the name of a related species which looks similar).

Occurrence

  • Currently only present above the 35.5ËšS latitude, in the Far North, Northland.
  • Found in pasture (primarily dairy and beef), roadsides and in unkept grassy natural areas.
  • Able to grow in a range of soil types and environmental conditions.
  • Does not like frost but can grow in frost-prone regions as an annual.

Life cycle

  • Plants can be annual or perennial depending on environmental conditions. In the frostless north most plants are functionally perennials. Plants surviving mowing or some herbicides have been observed to grow back in a more persistent, woody form.
  • A single plant can produce 30,000 seeds annually. Seeds have a pappus to aid wind dispersal. Most seed will fall nearby, for the related species Senecio inaequidens 8% of seed falls within 100 metres (the majority of that will fall by the base of the plant), but a small proportion of seed has the potential to be uplifted into wind currents and spread longer distances.
  • Seed will catch in places where wind slows (i.e. wind breaks, fence lines, buildings, trees and tall plants). Farmers have even observed seed growing in the gutters of their houses.
  • Seeds only germinate either on or very near (<5mm) the soil surface.
  • Seeds germinate in the largest cohort in autumn but can grow throughout the year if moisture is sufficient and there are gaps in pasture.
  • Most seed is ready to germinate on dispersal but a certain proportion of the seed will be darker brown or green in colour and will have increased dormancy. Seed usually persists three to five years in the seed bank but deeply buried seed may persist for up to ten years.
  • Plants can re-establish from root fragments and low-lying stems can put down roots. Pugging in wet weather will increase the likelihood of this happening.

Benefits

  • Madagascar ragwort has many flowers that are likely to provide food for pollinators, similar to common ragwort.

Similar species

  • Gravel groundsel (Senecio skirrhodon) is very closely related and at one point in the past Madagascar ragwort was considered to be that species.
  • Gravel groundsel has wider calycular bracts and often fleshier and less lanceolate shaped leaves (though leaf shape varies considerably in both species and leaf shape can change after mowing or grazing).
  • Common ragwort (Jacobaea vulgaris) first forms a rosette prior to bolting in the second year to become a much taller single-stemmed plant than Madagascar ragwort.
  • Neither Madagascar ragwort nor gravel groundsel have a rosette stage.

Status

  • Madagascar ragwort is classified as a pest in Northland in the Northland Regional Pest and Marine Pathways Plan (2017-2027).

Impacts on pasture

  • Its larger impact is in reducing pasture utilization, as stock avoid Madagascar ragwort plants and the forage plants growing close to them.
  • Gaps created by soil disturbance or left by dead pasture species (drought, pests) will be colonised by new seedlings.
  • Wind-dispersed seed can spread to neighbouring paddocks quickly.

Impacts on forage crops

  • Seeds can ‘catch’ in maize crops and will germinate in the autumn following harvest.

Impacts on stock

  • Like ragwort it contains toxins (pyrrolizidine alkaloids) that have the potential to poison stock. These are more dangerous to horses and cattle than sheep and goats.
  • Usually, it is only naive young stock newly exposed to the plants, or those that feed on hay containing the plants or eating sprayed plants (sugars increase when the plants are dying but toxins do not decrease) that are at risk of poisoning. Stock learn to avoid the plants.

Other impacts

  • Pyrrolizidine alkaloids can contaminate honey. This is unlikely to be an issue rot small scale infestations but if the weed spreads further and is uncontrolled there is potential for honey contamination.

Hand weeding

  • Hand weeding (pulling or grubbing) can be highly effective when done early in newly infested paddocks with few plants
  • Plants missed by spray should be hand weeded before they set seed
  • Plants should be bagged with care taken not to disturb seedheads
  • Carry a bag with you on farm vehicles
  • If done poorly (when plants are seeding) it can spread seed further
  • When there is a large infestation hand weeding becomes less effective as these paddocks would already have established a seedbank

Grazing management

  • Sheep and goats can graze Madagascar ragwort – they are about ten times less susceptible to its toxins than cattle.
  • Rotational grazing is more effective than continuous grazing.
  • Minimize soil disturbance as this provides an avenue for seedlings to germination and establish.

Pasture species

  • It is important to have a pasture that is competitive year-round.
  • Certain species might perform better in Northland. Kikuyu pasture is considered competitive however in autumn and winter it’s growth and competitivity reduces. Tall fescue (or other cool-season grasses) under-sown into kikuyu may increase pasture competitivity.
  • Increased diversity in pasture may aid competition against Madagascar ragwort.
  • Adding nutrients (i.e. superphosphate, urea) can increase pasture competitivity but will also increase the competitivity of Madagascar ragwort, so should be done in such a way that the pasture receives more benefit (don’t apply if pasture is poorly growing and Madagascar ragwort isn’t).
  • The pasture renovation process can be used to remove Madagascar ragwort seedlings by controlling them in stale seedbeds and annual crops.

Mowing

  • Usually mowing is not very effective.
  • Repeated mowing (mowing multiple times before the plant recovers) can be effective however it is time and resource intensive.
  • With mowing and slashing, if poorly timed it can spread seed.
  • It is important to clean machinery on leaving infested paddocks and especially not to use contaminated machinery in a clean paddock.

Cultivation

  • This is not usually recommended as Madagascar ragwort has a large seed bank and cultivation can bring seeds up for germination
  • However, if done right, a single deep burial of the top layers of soil has the potential to move most of the seedbank to a depth it cannot germinate from.

Chemical control

  • Seedlings and younger plants are far easier to kill than woody adult plants.
  • Young plants can be boom sprayed with several options including 2,4-D based mixtures.
  • Some of the recommended products and mixtures will damage clover.
  • Adult plants need to be spot sprayed with harsher chemicals that will also damage clovers and sometimes grasses.
  • Sometimes it can take months for larger plants to die.
  • Any sprayed plants should not be grazed before they are dead (browned off) to reduce the risk of poisoning stock.
  • Large and established infestation will require a sustained and ongoing programme that is seasonally times around germination peaks and using a rotation of chemical options.
  • Active ingredient When to apply Residual effect Grass damage Clover damage
    2,4-D Seedling to small plant Slight No Slight
    2,4-D amine + flumetsulam + Bonza® Seedling to juvenile plant Slight No Slight
    2,4-D amine + dicamba + Bonza® Seedling to juvenile plant Severe No Moderate
    MCPA Seedling to small plant Moderate No Slight
    Clopyralid Spot spray – larger plants Severe No Severe
    Dicamba Spot spray – larger plants Severe No Severe
    Triclopyr Spot spray – larger plants Severe No Severe
    Aminopyralid + fluroxypyr Spot spray – larger plants Severe Slight Severe
    Aminopyralid + triclopyr Spot spray – larger plants Severe Slight Severe
    Picloram + triclopyr Spot spray – larger plants Severe Slight Severe
    Aminopyralid + picloram + triclopyr Spot spray – larger plants Severe Slight Severe
    Metsulfuron Spot spray – larger plants Severe Moderate Severe
    Glyphosate Spot spray – larger plants None Severe Severe


    * Note that some of these herbicides have withholding periods but due to the poisonous nature of Madagascar ragwort, ANY sprayed pastures should not be grazed until the Madagascar ragwort has completely died down. Consult your farm consultant, industry rep or New Zealand Agrichemical Manual for more information about withholding period.
    ** Clover damage from any herbicide can vary greatly depending on clover growth, time of year and herbicide formulation, please read the label for specific information.

    Biological control

    Some biological agents have been noted on Madagascar ragwort in New Zealand but have not been observed to have a major impact to date, the reasons for which could be beneficially investigated. Others not yet in New Zealand require comprehensive risk analysis and host specificity trials.

    • The rust fungus Puccinia lagenophorae is found in Northland and can reduce the amount of stems formed (and therefore seedheads).
    • The gall fly Sphenella ruficeps, also found in Northland, infests seedheads and eats all seed.
    • The ragwort aphid Aphis lugentis, was also recorded on Madagascar ragwort in Northland.
    • The moth Secusio extensa is not present in New Zealand but was ruled out for lack of host specificity.
    • Further survey in the native range of Madagascar ragwort is needed to identify other potential biocontrol agents.

     

Further information

  • Dymock JJ, Winks CJ. 2024. Invertebrate and fungal associations of the pastoral weed, Madagascar ragwort, Senecio madagascariensis Poir, in Northland, New Zealand, and implications for biocontrol. New Zealand Journal of Agricultural Research: 1–10.
  • Agrimedia. 2025. New Zealand Novachem Agrichemical Manual. Agrimedia Ltd, Christchurch, New Zealand.
  • Popay I, Champion P and James T 2010. An illustrated guide to common weeds of New Zealand. New Zealand Plant Protection Society, Lincoln, New Zealand. 416 pp. ISBN 978-0-472-16285-6.
  • Schmidt-Lebuhn A, Egli D, Grealy A, Nicholls J, Zwick A, Dymock J, Gooden B. 2022. Genetic data confirm the presence of Senecio madagascariensis in New Zealand. New Zealand Journal of Botany 62.