Seriphium plumosum ( = Stoebe vulgaris)/ Bankrupt bush / Bankrotbos / Slangbos
Dense bankrupt bush infestation in old pasture land
Description: A dense, straggly-branched woody shrub, grey in colour, up to 1m in height and width, often with small puffy white galls, not to be confused with its small brown / pale purple flowers; resembles lavender or fynbos.
Individual bankrupt bush White galls on bush
Origin: Probably Cape fynbos region, although it might always have been present further north; through overgrazing and fire exclusion, it has migrated rapidly through the Karoo and Northern Cape into Free State and North West and now into the Waterberg, where it has become widespread in historically overgrazed areas.
Occurrence: On roadsides and in open grassland, especially along margins of open wetlands and vleis. Serious infestation in many old pastures and where veld has been overgrazed.
Why it is a problem: it is unpalatable to stock and game and once established in grassland, becomes a serious invader that causes degradation of veld, seriously diminished carrying capacity (hence the name bankrupt bush) and reduced biodiversity. The result is material devaluation of the land. It is also highly inflammable and aggravates the spread of uncontrolled veld fires.
As an indigenous shrub, it is not registered nationally as a declared invader. However, it has become a serious problem in the semi-arid sourveld of the Waterberg and should be strictly controlled in the interests of the landowner.
Elimination / Control Methods: Irrespective of the method adopted, control is a long-term process, requiring annual campaigns to eliminate re-growth and remove newly germinated plants. This is due to the resilience of the root system, in particular a strong, deep tap root, which enables the plant to survive being burned, cut or partially excavated.
Physical removal by excavation is the most certain way of removing the plant, as long as the whole root system, including the tap root, is excavated. This should be done in the rainy season, when the ground is moist enough to allow removal of the whole root system. The accumulated vegetation should be burned in an open area where it will not ignite surrounding veld. However, while well-suited to sporadic occurrences or small stands, this solution may be impractical in the case of dense or widespread infestation.
Burning or cutting alone (with a tractor-mounted slasher) does not eliminate the plant; on the contrary, it seems to promote regeneration. A combination of burning / slashing in late winter, followed by spraying of new growth with herbicide (see below) in spring has proved to be successful, provided there is annual follow-up treatment. There are many examples in the Waterberg where seemingly hopeless infestations of the plant have been eradicated with diligent repeated treatment. (There are unfortunately, many more examples of pastures abandoned to the weed).
Herbicides should be applied early in the growing season, especially immediately after burning or slashing. In large open areas, such as in the Free State, herbicides are often applied aerially, but this indiscriminate method of application also results in the elimination of other, desirable indigenous woody plants. Alternatives include application by tractor, or manually using backpack spray units.
- All require the addition of a surfactant (which includes a wetting agent), the name of the preferred one usually being given with the instructions for use;
- All herbicides should be used when freshly mixed (do not leave the solution overnight).
- NB: Follow carefully the instructions provided on herbicide label. Many herbicides can be toxic to other plants and or game and livestock if used inappropriately. (Mis-use of herbicides is also a criminal offence in terms of Act No. 36 of 1947).
Several herbicides are registered for the control of bankrupt bush:
- Forester (formerly called Climax) (metsulfuron methyl 600g/kg) (L8891):a wettable powder. Use the surfactant H&R Crop Oil (L6802)). Apply to foliage.
- Brush-Off (metsulfuron methyl 600g/kg WG (L4535): a granular powder. Use with surfactant EOS oil; and wetting agent Wetcit. Apply with a back-pack sprayer to foliage of actively-growing plants early in summer.
- Limpopo(tebuthiuron 500g/l)(L7199):a suspension concentrate.*
- Molopo(tebuthiuron 500g/kg)(L5854): a suspension concentrate. Dilute 1.5 l in 8.5 l water and apply small doses (1-2ml) to the soil at the base of each plant before or during the rainy season. The herbicide relies on rainwater to carry it to the roots.*
*NB: Tebuthiuron is known as a soil sterilant and can damage surrounding woody vegetation for many years after its application. It should only be used under the close supervision of a herbicide specialist.
Common salt, recommended by some sources, is not advised as a means of eliminating bankrupt bush, because it affects the soil, upsetting the mineral balance, pH and soil micro-organisms.
ARC-LNR SAPIA News 28 (April 2013). ARC – Plant Protection Research Institute, Pretoria. www.arc.agric.za
Bromilow, Clive (2010): Problem Plants and Alien Weeds of South Africa. Briza. Pretoria
SA Koöp / SA Co-op Vol.29 No. 6, August/September 2012
Van Zyl, Kathy (compiler) (2005): Control of Unwanted Plants. Xact Information, Pretoria.
Special thanks to Dr Gerhard Verdoorn of Griffon Poison Information Centre, to Mr Ferdie Jordaan of Arysta Lifescience and to Ms Lesley Henderson of ARC for their invaluable advice and guidance. Their enthusiastic support for this voluntary project is greatly appreciated.