Mauritius thorn (Caesalpinia decapetala) (Fabaceae)

Afrikaans: kraaldoring

The weed

Mauritius thorn is a thorny, woody, clambering shrub with bipinnate leaves and clusters of pale yellow flowers.  Large, globular seeds are produced in flattened, unsegmented, beaked pods. Its exact centre of origin is still unknown, and whereas it is certainly not indigenous to Mauritius, as its common name would suggest, its native range might include Indonesia and Malesia (including the indo-Malaysian archipelago and northern Australasia). In South Africa it was initially grown as a component of security hedges and has now become widespread from the Limpopo province in the north, through Mpumalanga, the neighbouring country Swaziland, KwaZulu-Natal and Eastern Cape provinces. It invades grazing land, commercial plantation, riparian vegetation, forest margins and savannas in the moist eastern parts of the country, where it forms impenetrable, prickly thickets, injures animals and humans, causes trees to collapse, uses excessive amounts of water and increases fire risk.

Mauritius thorn flowersMauritius thorn infestationMauritius thorn pods


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

Several herbicides have been registered for use against Mauritius thorn, mainly targeting plants up to 1 m in height, but access to plants growing in the canopy of tall trees is problematic. Surveys to identify promising biocontrol candidates were initiated during the 1990s, but have resulted in the release of only one insect species: the seed-feeding beetle Sulcobruchus subsuturalis. Despite the release of more than 350 000 beetles at more than 200 different localities in South Africa, evidence indicates that they are reproducing in the field in very low numbers only, and at a limited number of sites. The investigation into a second candidate agent, the leaf-mining moth Acrocercops hyphantica, was terminated before conclusive results had been obtained, but might be revived again if the opportunity arises.

More information

Copies of the following scientific reviews on Mauritius thorn and its biological control can be downloaded:
o 1999 pdf​
o 2011 pdf
Copies of the following leaflets can be downloaded:
o Caesalpinia decapetala pdf​​
o Sulcobruchus subsuturalis pdf

Contact  Marcus J. Byrne, University of the Witwatersrand, E-mail: marcus.byrne@wits.ac.za​