Ecological risk assessment of tebuthiuron following application on northern Australian wetlands
Internal Report 362
van Dam RA, Camilleri C, Turley CJ & Markich SJ
Supervising Scientist Division
About the report
The herbicide tebuthiuron is commonly used in Australia’s Northern Territory to control the wetland weed, Mimosa pigra. The present study provided a probablistic ecological risk assessment of tebuthiuron to freshwater fauna and flora of northern Australian wetlands. The following two working hypotheses were assessed: (i) that tebuthiuron may result in direct adverse effects to native freshwater biota at the site and downstream of treated M. pigra infestations, potentially resulting in adverse effects to community structure and function, and (ii) that long term and/or delayed effects to native freshwater biota may occur as a result of the residual properties of tebuthiuron. Indirect effects of tebuthiuron were recognised but could not be quantitatively assessed.
Effects characterisation involved assessment of the acute or chronic toxicity of tebuthiuron to five local freshwater species (three animals and two plants), and comparison of the results with toxicity data derived for northern hemisphere species. Chronic no-observed-effect concentrations (NOECs) for local plant and invertebrate species ranged from 0.05 to 50 mg L-1, while the acute (96 h) LC50 of a local fish species was 214 mg L-1. The data were similar to those derived for northern hemisphere species.