Problem Statement: Salvinia molesta occurs naturally in South America but has become a serious invasive water weed in Africa, Australia, Papua New Guinea, Indonesia, Malaysia, Sri Lanka and Southern India. In the mid 1980s, an entomologist from the Department of Agriculture, Thailand, upon a directive from the Ministry of Agriculture & Cooperatives, proposed a project on biological control of this weed in Thailand. The weevil Cyrtobagous salviniae (from South America), successfully introduced as a biological control of S. molesta in Australia, was proposed for testing and release. The proposal was sent to local taxonomists for review and evaluation.

Methods: Locally available taxonomic experts were able to show that S. molesta did not occur in Thailand. The locally occurring Salvinia species had been misidentified and was in fact S. cucullata, a species very similar in morphology and appearance to S. molesta, but smaller in size and less weedy.

Outcomes and Impacts: The local taxonomists informed the relevant government officials that S. molesta did not occur in Thailand and that an eradication programme was therefore unnecessary. The proposed biocontrol project was thus withdrawn. Should the correct and timely identification of this weed not have been made, the Royal Thai Government could have spent at least the budgeted US$5million and a period of no less than 5 years implementing a wholly unnecessary biocontrol project.

Lessons: The timely use of taxonomic expertise resulted in the prevention of government spending millions on an unnecessary biocontrol programme.