Recently on ‘Burke’s Backyard’ Don explained the dangers of fireweed, a pretty yet poisonous yellow flowering weed that is often found in paddocks and pastures. This plant is poisonous to both horses and donkeys, and other livestock can also suffer from this widespread weed.
Botanical name: Senecio madagascariensis
Common name: Fireweed
Description: Fireweed is an annual herb (that is a small plant) which originates from Natal in South Africa. It was first reported in the Hunter Valley of New South Wales in 1918.
This weed has an erect habit growing up to 50cm (20″) tall, but may be smaller in dry or harsh conditions (10-20cm or 4-8″ tall). The plant has mid-green leaves on branched stems but its main characteristic is the mass of small yellow daisy flowers which are seen mainly from winter to spring. The flowers are a golden yellow and have 13 petals surrounding the yellow centre. Seeds form quickly on the plant.
How does it spread? Each fireweed plant may produce as many as 30,000 seeds as a single yellow flower can produce between 100-150 seeds and there can be as many as 200 flowers per plant. The seeds are white and feathery and are often dispersed by wind but can also be spread by the movement of animals and birds. Fireweed can also be spread via mulch and feed.
Who is at risk? Horses, donkeys and cattle face the greatest risk of poisoning from this plant. Poultry can also be affected after eating fireweed. Sheep that eat fireweed may experience a higher copper intake resulting in liver damage. No significant damage to sheep may be noticed until the animals have been exposed to the weed for two or more seasons. Goats can also be affected but, as with sheep, may require at least two seasons of exposure before symptoms are noticed.
Symptoms of poisoning: It is compounds called alkaloids which make fireweed toxic to many herbivores (plant eaters). The major effect of fireweed is that it causes severe liver damage but other problems include:
- some gradual weight loss
- fluid on the lungs
- blindness may occur
- may cause severe liver damage
- sudden death without any other indications
Neurological symptoms may also be apparent as an early indication of poisoning. These include:
- twitching of the head muscles
- inco-ordination of movement
Horses will vary in their susceptibility to the alkaloids and it may take from several weeks to several seasons of exposure to this plant before the animals show any signs of illness. Be aware, though, that some horses may also have a more acute reaction to it.
Treatment: It is important to call your vet immediately if you suspect that your horse has eaten fireweed and to remove the animal from the infested paddock.
Fireweed is common along coastal New South Wales into southern Queensland (see map). It is usually found in heavily grazed pastureland and may spread into bushland after fires. It is also found along road verges. It has been found throughout south-east Queensland in shires around Brisbane and as far north as Noosa (it is spreading along the Bruce Highway and the Sunshine Motorway) and as far west as the Great Dividing Range. As well as being found along the New South Wales coast to Bega it is also found in parts of the Northern Tablelands and Western Slopes of New South Wales. Plants have been recorded around Mudgee and Dubbo in the Central West. It is beginning to be noticed in Victoria around Gippsland.
There is no one way of eliminating fireweed but a combination of physical and chemical controls will reduce infestations in large areas such as paddocks and pastures. In a home garden situation plants can be hand-weeded or mown. Whichever control methods are selected it is vital that they occur before flowering to reduce seed production. Seeds can form even after treatment with herbicide or weeding if the plant is already in flower so dispose of hand pulled weeds in the garbage.
Regular slashing is an important method of controlling this weed (particularly before flowering and seeding occurs).
Regular spraying of pastureland with selected herbicides may help control fireweed. Chemicals recommended by the Queensland Department of Primary Industries and NSW Agriculture include Bromoxynil (sold as Bromocide 200, Brominil 200 and Buctril 200). The herbicide should be applied on young plants before flowering. More chemical is required on flowering or mature plants and control is less effective. For more details on herbicide control, rates and products consult the Queensland Department of Natural Resources or NSW Agriculture (details below).
CSIRO is currently working on a biological control method for fireweed. Some pests and a fungus already attack the weed but will not control it.
Improving pastures to increase competition against the weed is also important for on-going control.
Other yellow-flowered weeds
There are many yellow-flowered pasture weeds including capeweed (Arctotheca calendula), stinking Roger (Tagetes minuta) and gorse (Ulex europaeus) as well as other species of senecio such as groundsel (Senecio vulgaris and S. lautus, which is a native plant) but it is fireweed that is considered dangerous to animals and should be carefully noted.
A Pest Fact sheet is available from the Department of Natural Resources in Queensland on fireweed, which is a declared weed in that state. To receive information contact the department direct. Phone: 13 2523 (within Queensland); 1800 803 788; or (07) 3406 2867.
NSW Agriculture also has an Agfact (P7.6.26) on fireweed, currently out of print but being reordered. Photocopies would however be available from your local NSW Agriculture office or by phoning the head office. Phone: (02) 6391 3100. Copies can also be ordered of this and other Agfacts from the internet at the following address: www.agric.nsw.gov.au. The ‘Fireweed Agfact’ costs $3.50 (postage is $2.00). A new publication on the chemical control of noxious weeds, including fireweed, will also be available shortly from NSW Agriculture.
CSIRO Handbook of Australian Weeds (CSIRO Publishing, 1997, $49.95). This book is available from CSIRO Publishing. For mail-orders add $8 for postage and handling and allow two weeks for delivery. Send payment with orders.
PO Box 1139
Collingwood Vic 3066
Phone: (03) 9662 7666
Fax: (03) 9662 7555
Home page: http://www.publish.csiro.au