The Use of Biological Control Agents for the Control of Plant Invaders and the Importance of Partnerships

The USA and South Africa are among the world’s leading biological weed control countries. By 1998, seventy-three biocontrol agents had been released on thirty-six weeds in USA mainland and by 1999, eighty-two agents on forty-seven weeds in South Africa. The early Hawaiian projects served as a training school and source of tested biocontrol agents for other countries. In South Africa, nineteen of the target weeds for biocontrol are woody invaders, compared to only two woody species in USA. Most of the woody invaders in South Africa are economically important, eliciting conflicts in interest typical of South Africa. The two countries need each other’s assistance to control invasive species originating from each other’s country, e.g. Delairea odorata Lemaire and Carpobrotus edulis (L.) L. Bol., which are among the top ten weeds in USA, and Prosopis spp., among the worst invaders in South Africa. The USA and South Africa already co-ordinate their research on certain invasives they have in common, they share facilities and co-operate on contract basis. Off-target feeding by some biocontrol agents in both countries forced researchers and decision-makers to be more critical, and resulted in the revision of the protocols regarding release of new agents.