Can failure be turned into success for biological control of mile-a-minute weed (Mikania micrantha)?

Abstract

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 dif-ferent release strategies. Other insect natural enemies were considered worth evaluating for host specificity and effectiveness, but failure of the thrips discouraged further invest-ment. 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 introduc-tion and a broad range of neotropical isolates is currently under glasshouse evaluation.