A declaration application will soon be submitted to NSW DPI for a Class 3 classification. Class 3 noxious weeds must be fully and continuously suppressed and destroyed and the plant may not be sold, propagated or knowingly distributed.
Why Is It Bad?:
Mother of Millions will establish readily in run down pastures where competition levels are low. It is estimated that infestations are capable of increasing their size by 20-30% per year. Once established, it readily spreads and can dominate a site before control work is even considered.
The biggest problem the Mother of Millions presents to landholders is it’s toxicity to stock, humans, and other animals such as household pets, with dogs especially vulnerable. The plant contains the toxin bufadienolides which eventually causes heart failure. The flowers contain approximately 5 times as much toxin as the rest of the plant and so flowering periods are of the most concern. If stock are hungry or unfamiliar with the area, they are more likely to try new plants and there is an increased risk of consumption even though the plant is generally unpalatable. Symptoms of poisoning include dullness, loss of appetite and diarrhoea. If only a small amount is consumed then livestock can generally recover but treatment must be immediate. Treatment is expensive and must be administered by a veterinarian, leading to more costs.
As a succulent, Mother of Millions is highly adaptable to dry conditions and can survive long drought periods. It is for this reason also that it is so difficult to eradicate. Use of herbicides must also include use of the correct wetting agent. The waxy exterior prevents most herbicides from penetrating and having the desired effect on the plant.
Leaves are linear and cylindrical with a groove on the upper surface, growing to 3-10cm long. They are numerous and grow in pairs or threes. They are purplish and mottled brown, initially erect then horizontal or drooping. There are 4-7 projections or teeth at the end of each leaf. Leaves drop readily and buds in the tips quickly take root, forming new plants.
Flowers occur in clusters, 10-12cm in diameter, at the end of stems. They are usually orange to red but can also be whitish yellow. Flowers are tubular with 4-5 lobes, and grow to 2.5cm in length. Flowering usually occurs during the winter months, from March to September.
Fruit is dry, papery, consists of 4 segments, and is about 1cm in length. Each one contains many minute seeds which survive in the soil seed banks for many years.
Small infestations can be removed by hand if special care is taken to remove all plant material, which should then be burnt or placed in plastic bags and buried in landfill.
Use of herbicides can be very costly as the efficacy can be highly affected by use of the wrong, or no, wetting agent. A wetting agent is required to penetrate the waxy outer layer of leaves and stems. Although plants can generally be sprayed at any time of year, efficacy is increased during active growing periods such as flowering, when it is also easier to spot plants. NSW DPI recommends use of Triclopyr + Picloram herbicides during flowering, Fluroxypyr for use on seedlings and young plants before flowering, or 2,4-D Amine. Chemical control is recommended as a follow-up treatment after use of fire control. It is important to note that plants can become more palatable to stock after herbicide application but contact should be avoided as dead plants are still poisonous and should be removed or burnt.
Fire will kill plants as well as a large proportion of the soil seed bank. Burning of plants can also be used to decrease desirable growing conditions by reducing debris levels, and to encourage growth of competitive grasses. Infestations have been reported as decreasing by 30% per year through use of fire and follow-up chemical control.
Slashing & Cutting:
South African citrus thrips is present in Queensland where it reduces the number of plantlets and flowers formed by damaging the outer tissue. Populations of thrips vary from year to year and should only be used as part of an integrated management program; they cannot be used as a sole control method.
Further research is required before another potential agent, a stem-boring weevil (Osphilia tenuipes), is released as there are current concerns about off-target damage. Other potential agents tested were declared unsuitable.
Cultivation & Scalping:
Maintaining strong pasture competition is seen as the best long term non-chemical option for controlling Mother of Millions infestations.
Successful treatment programs rely on ongoing monitoring of sites. Regrowth and new seedlings can easily become larger infestations if follow-up treatments are not part of the management program. All land managers should take into account the effects weed control can have on the surrounding flora when considering their options.
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Image Credit: Ashley Bullock
Image Credit: Ashley Bullock Narromine Shhire Council