Photo guide to weeds

Fireweed (Senecio madagascariensis)

  • Photograph of the yellow daisy-like flowers of the fireweed plant
    Fireweed flowers
  • Photograph of a fireweed plant in flower
    Fireweed

General information

Fireweed is an introduced daisy-like herb native to southern Africa. Fireweed was first recorded in Australia in the Hunter Valley in 1918. It is thought that fireweed arrived in the ballast of ships trading between Australia and Europe via Capetown. Fireweed spread slowly at first, but in the past 30 years has rapidly increased its range, most likely aided by modern transport and rural practices.

Fireweed is a Class 2 declared pest plant under Queensland legislation.

Scientific name

Senecio madagascariensis

Similar species

Fireweed can easily be mistaken for the closely related, native Senecio spp. particularly Senecio pinnatifolius and Senecio brigalowensis. Senecio brigalowensis is increasingly abundant and weedy in central Queensland from Roma to Rockhampton and will also cause cattle poisoning.

Description
  • Annual or short-lived perennial.
  • Varies greatly in size and shape depending on conditions.
  • In dry harsh conditions may be less than 20cm tall with narrow leaves, no branching and few flowers.
  • In ideal conditions, grows up to 50cm tall with multiple branches, long wide leaves (6cm x 2cm) and about 100 flowers.
  • Leaves 2-6cm long, alternate, dark green, with serrated margins.
  • Flowers bright yellow, daisy-like with a diameter of about 2cm, producing up to 100 seeds each.
  • Each seed 2-3mm long and cylindrical in shape with rows of very fine short hairs and a silky pappus (parachute).
  • Shallow-branched tap root with many fibrous roots.
Habitat
  • Seeds germinate in mild, warm conditions in the presence of light and moisture.
  • Light infestations can produce a million seeds per hectare.
Distribution
  • Native to southern Africa.
  • Occurs in beef and dairy pasture east of the Great Dividing Range.
  • Established along the entire New South Wales coast and north to Brisbane.
  • Isolated infestations found near Caboolture, Cooroy, Belli Park, Maleny, Yandina, Pelican Waters and as far north as Gympie.
  • Could potentially infest extensive areas of valuable pasture north of Brisbane to Rockhampton.
Life cycle
  • Seedlings appear between March and June, growing quickly to produce first flowers in 6-10 weeks.
  • Begins to die back in spring.
  • Dry summer followed by autumn or winter rains leads to heavy infestations.
Spread
  • Seeds spread by wind, stock, in pasture seed, hay, turf, mulch and with stock transport.

Impacts

Economic

  • Competes with pasture species.
  • Toxic to livestock, particularly cattle and horses, causing illness, slow growth and poor conditioning which can result in death.
  • May taint meat and milk.
Prevention
  • The best form of weed control is prevention. Treat weed infestations when they are small - do not allow weeds to establish.
  • Ways to prevent weed spread
Control

Physical control

  • Prevent establishment by ensuring dense cover of pasture in autumn and winter.
  • Remove small infestations immediately.

Mechanical control

  • Chip out, bag and burn isolated plants. Gloves should be worn when handling fireweed plants.
  • Slashing usually not effective, as increases poisoning risk to stock and only delays flowering and seeding.
  • Cultivation is not recommended.
  • Fireweed remains toxic after being cut and becomes more attractive to stock.

Herbicide control

  • Spray herbicides before plants reach maturity. However, application during flowering will be effective if higher recommended rates of herbicide are applied.
  • Research is ongoing for herbicide controls, including residual control methods. Trials have shown herbicide application in the autumn period during April provides good control. Before undertaking such programs landholders are advised to determine the infestation levels.
  • Effective application method in an open pasture situation is a boom spray. Follow this up by spot spraying, or pulling and bagging any regrowth or missed plants.
  • Boom spraying is also suitable for follow-up treatments, as it allows destruction of immature plants, which may otherwise grow to re-seed the area before they can be noticed.
  • Bromoxynil (trade names Bromicide 200, Brominil 200 and Buctril 200) is suitable for use in pastures containing clovers, medics and lucerne, and it will not affect grass.
  • Bromoxynil is effective if used on seedlings, which usually appear in autumn and early winter but may appear later following rain. Twice as much bromoxynil is needed if it is applied to plants that are just beginning to flower. Bromoxynil is less effective on mature plants, as it is a contact herbicide only. Mature plants will only be killed off where the bromoxynil comes into contact with the plant, allowing recovery of the plant from lower, untouched portions.
  • Follow-up inspections every four months after initial treatment is recommended. Re-treat as required.
  • Unfortunately, fireweed control is often not considered until the highly visible flowers appear and it is too late for effective control with herbicide.
  • See the fireweed fact sheet (PDF, 583.5KB) for herbicide control and application rates.

Biological control

  • Organisms can be found attacking fireweed, but any effect they have is temporary and isolated.
  • Orange rust (Puccinia lagenophorae) is common and often affects fireweed, particularly in lower country.
  • Blue stem borer moth (Patagoniodes farinari) is also common, but the larvae usually develop too slowly to have an impact.
  • Two moths imported from Madagascar were host tested. In controlled tests they were found to feed on important non-target plants so no releases were made.
  • Other potential biological control agents have been identified, but rigorous testing is needed to ensure that they do not feed on closely related Australian native plants. Investigations in South Africa are presently being undertaken.
Declaration details
  • A declared Class 2 species under the Land Protection (Pest and Stock Route Management) Act 2002.
  • Taking for commercial use, introduction, keeping, releasing and supplying (including supplying things containing reproductive material of this pest) is prohibited without a permit issued by Biosecurity Queensland.
  • Landholders are required to control declared pests on their properties.

Further information

Last updated 08 April 2013