Biological control of giant sensitive plant (Mimosa pigra) in Southeast Asia

• Malaysian Agricultural Research and Development Institute, Malaysia
• BIOTROP, Indonesia
• National Institute of Plant Protection, Vietnam

Mimosa pigra, giant sensitive plant, is native to tropical America and has invaded wetlands in tropical Southeast Asia and the Northern Territory of Australia. M. pigra occupies about 700 square kilometres in the Northern Territory. It has the potential to dominate about 20% of the Kakadu National Park and the valuable wetlands of Arnhem Land and could invade the eastern seaboard as far south as northern NSW.

In Thailand, the weed causes severe problems in irrigation systems, reservoirs and fallow rice paddies. Rapid increases in the size and spread of infestations are occurring in Malaysia, Vietnam and Indonesia and climatic predictions show that the weed has the potential to become a major problem in important conservation and primary industry areas.

In Malaysia, the chemical and mechanical methods used to control the plant in crop lands have been estimated at $0.15 per plant, a sizeable cost when many thousands of plants are involved.

The escalating costs in providing long-term sustainable weed control using chemical and mechanical means are causing concern throughout the region. There is also an increasing awareness of the long-term effects on the environment following the use of residual herbicides.

The aim of this project is to assist in the development of a long term sustainable integrated weed management system involving biological control agents for the partner countries.

This project builds on this Australian research by extending the use of the biological control agents into partner countries for the long-term sustainable control of M. pigra.
The major sub-projects aim to:

survey the spread of M. pigra in each country to determine its impact on agriculture, industry and the environment. This will provide information for the distribution of the biological control agents and for an economic assessment of the problem. Seeds from the weed will also be collected for assessment (as part of another project) to determine the genetic diversity of the weed throughout the region;

release new (and possibly re-release existing) biological control agents into partner countries following assessment of the host range for each agent. This will require transmission to partner countries information and techniques for rearing and testing for host-specificity. These procedures are also appropriate to other biological control programs; and

monitor the establishment of the control agents and share this knowledge with other workers involved in biological control projects.