Introduction

The South American Solanum mauritianum Scopoli (Solanaceae) comprises an unarmed, branched shrub or small tree, 2-4 m tall, which threatens many commercial activities and natural habitats worldwide, particularly in subtropical and tropical regions (ISSG, 2006). Introductions of the plant have occurred via several routes, notably accidental transfer by seafaring human colonists, deliberate importations for ornamental purposes, and longdistance dispersal by frugivorous birds (Roe, 1972; ISSG, 2006). Known by several common names worldwide, the most important being bugweed, tree tobacco, and woolly nightshade, the plant is emerging as an important environmental weed in many countries (Florentine and Westbrooke, 2003; PIER, 2005; ISSG, 2006).

In South Africa, where the weed has proved to be particularly invasive, infestations affect agricultural lands, forestry plantations, riverine habitats, and conservation areas, particularly in the eastern, higher rainfall regions of the country (Henderson, 2001). The high weed status of S. mauritianum in South Africa resulted in its targeting for biological control in 1984 (Olckers and Zimmermann, 1991). South Africa is currently the only country that has fully implemented a biological control program against S. mauritianum, including exploration for candidate agents, host-specificity testing and release and establishment of agents (Olckers, 1999). New Zealand has recently funded research on some of the agents that have been used in South Africa and may soon consider the importation of the most promising species (Withers et al., 2002; Borea, 2006).