Can Failure be Turned into Success for Biological Control of Mile-a-Minute Weed (Mikania micrantha)?

Research into biological control of Mikania micrantha Kunth (Asteraceae) started in 1978, concentrating on insect agents. Host specificity studies on the first agent, Liothrips mikaniae (Priesner) (Thysanoptera, Phlaeothripidae) from Trinidad were completed by 1982, and the thrips was released in the Solomon Islands in 1988 and, subsequently in Malaysia in 1990. Neither release led to establishment, and possible reasons for this are discussed, including the impact of generalist thrips predators and the effectiveness of different release strategies. Other insect natural enemies were considered worth evaluating for host specificity and effectiveness, but failure of the thrips discouraged further investment. A new initiative started in 1996, in collaboration with the Kerala Forestry Research Institute (India) and Viçosa University (Minas Gerais, Brazil), to assess the weed problem in the Western Ghats of India and to develop classical biological control based on exotic coevolved fungal pathogens as part of an IPM programme. A rust pathogen, Puccinia spegazzinii de Toni (Uredinales), has been selected as the prime candidate for introduction and a broad range of neotropical isolates is currently under glasshouse evaluation. The rust has demonstrated total specificity to M. micrantha (38 non-target species currently screened), is highly damaging (leaf, petiole and stem infections leading to cankering and death) and has a broad environmental tolerance. Progress on biological control of this and other weeds of developing countries is discussed in light of the availability and continuity of funding. Comparisons are drawn between the developed world where a long-term commitment with adequate funding is now generally recognised as necessary, and the developing world, where short-term donor funding makes long-term funding difficult or impossible to obtain. In future, those concerned with funding solutions to invasive weeds in developing countries need to recognise the long-term nature of this work.