Silver-leaf nightshade (better known in South Africa by its Afrikaans common name, satansbos), a plant indigenous to the south-western USA and northern Mexico, has annual stems and a perennial, deep, spreading root system. The silvery-green leaves have wavy margins, are often folded upwards along the midrib, and the whitish under-surface is usually armed with reddish prickles. Mauve, blue or even white flowers give rise to shiny green berries with white patches, approximately 12 mm across, which turn yellow when ripening. Propagation is mainly vegetative, by means of regeneration from small root fragments, but the dispersal of seeds in the dry berries is responsible for long-distance dispersal.

In South Africa, satansbos is a major agricultural weed of arable and pastoral lands, and not a true invader of undisturbed, natural vegetation. It affects crop yields through competition, and disrupts tillage and harvesting practices, is extremely difficult to control, and is reported to be toxic to livestock, especially cattle. Certain farmers, however, regard it as a valuable pasture crop.  

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In terms of the Alien and Invasive Species Regulations (AIS), National Environmental Management: Biodiversity Act (Act No 10 of 2004), satansbos was declared a category 1b species, which necessitates its control or removal and destruction if possible. No trade or planting is allowed.

Satansbos is notoriously difficult to control, due to its extensive root system, the tiniest segment of which can regenerate into a complete new plant. Cultivation of a mildly invaded field can result within a short time in a dense mono-specific stand of satansbos. Chemical control is hampered by the small leaf surface available for absorption, in relation to the enormous root surface that needs to be killed by the translocated chemicals. One registered herbicide exists in South Africa for the control of satansbos.  

Decades of research into suitable biocontrol agents culminated in the establishment of two host-specific, leaf-feeding beetle species, Leptinotarsa texana and L. defecta. These are effective defoliators, but only reach damaging population numbers intermittently, and tend to migrate as soon as one patch of the weed has been defoliated. The presence of the insects needs to be integrated with suitable land management practices in order to maintain  populations of the weed at an acceptable level. No more research into this weed species is being carried out currently.

• Copies of the following two scientific reviews on the research into the biological control of satansbos can be downloaded:

• Leaflets on the following topics can be downloaded:

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