24 Plant Protection Quarterly Vol.22(1) 2007 Summary Two subspecies of Chrysanthemoides

monilifera (L.) T.Norl. (boneseed), have been introduced to Australia from South Africa and are now among our worst en-vironmental weeds. A biological control program was established in 1987 to com-bat these two invaders. To date, six spe-cies of insects have been released on bitou bush, four of which have established. The bitou tip moth (Comostolopsis germana Prout) and bitou seed fly (Mesoclanis po-lana Munro) are now widely established in New South Wales and two other agents, the bitou tortoise beetle (Cassida sp.) and the bitou leaf roller (‘Tortrix ’ sp.) are cur-rently surviving in low numbers in New South Wales but only in the vicinity of their initial release sites. A total of six spe-cies have been released for boneseed, but despite repeated and often large releases, none of these agents have established in the field. Predation by indigenous inver-tebrates is suspected as being a key factor in preventing establishment of the foliage feeding agents in Tasmania, South Aus-tralia and Victoria. The leaf buckle mite, Aceria sp., is one of several additional agents being investigated for the control of boneseed; it was approved for field re-lease in 2005. Despite the failure of several agents to establish in the field, especially on boneseed, the biological control pro-gram has delivered some successes. The pending release of the leaf buckle mite and the targeted selection of future agents specifically for boneseed should help to counteract previous setbacks