Control of giant sensitive plant Mimosa pigra

• National Biological Control Research Center, Thailand

Since its introduction into Australia in 1976, the Central and South American giant sensitive plant, Mimosa pigra, has already developed into a significant and potentially very serious weed in the Northern Territory. This thorny, tall woody perennial could invade and seriously disrupt use of most wetlands and seasonally inundated land in Australia as far south as the Tropic of Capricorn. It causes even greater problems in Thailand, where it has formed huge impenetrable thickets in the north and is spreading rapidly along the river systems. It is also posing a threat in other parts of Southeast Asia and in Africa.
Consequently, this project aims at developing strategies for controlling M. pigra in different ecological and climatic conditions. Australian scientists have conducted an exploration for potential biological control agents in the plant's native rangelargely in Braziland imported three species of leaf-eating chrysomelid beetle and one seed-destroying bruchid as result. These are currently being evaluated and monitored in Brisbane and the Northern Territory, with the support of CSIRO, NT/DPP and ACIAR. Preliminary surveys elsewhere in the native ranges. From these, and others collected during more detailed surveys, the scientists will select species that show promise, grouping them into complexes suitable for control of the weed in different ecoclimatic situations. An Australian entomologist is based in Mexico, with support from ACIAR, to study additional potential biocontrol agents.
Research in Thailand includes assessment of the needs and expectations for management of M. pigra in different areas, and processing of information on climate, seasonal growth of the weed, local control methods and base-line data on selected infestations. After completing this work, the Thai scientists will introduce the selected biological control agents into Thailand, propagating, distributing and monitoring them.
Research on herbicidal control, initially in the Northern Territory, will include the effects of different management regimes, studies on interaction between herbicides and biological control agents and, in the longer term, integration of biological control agents and, in the longer term, integration of biological, chemical and other control practices to achieve economic and effective management.
Finally, in conjuction with Thai authorities, the project will develop a broad management strategy for the control of M. pigra in Thailand, to ensure effective implementation of the results.