|
(M/FF226) Toxicity of sulfosulfuron, a novel sulfonylurea herbicide, to aquatic plants. Davies, Joanna1, Tencalla, Francesca2, Honegger, Joy2, Brain, Philip1, Newman, Jonathan3, Pitchford, Hannah1, 1 2 3 ABSTRACT- Sulfosulfuron is a selective, post-emergence, sulfonylurea herbicide intended for use in winter wheat at a rate of 20 g/ha. Under worst-case UK soil and weather conditions, sulfosulfuron may potentially enter the aquatic environment via drain flow from recently treated, artificially-drained fields. Laboratory testing has shown that, as expected for a herbicide, aquatic plants are amongst the most sensitive aquatic species to sulfosulfuron. Information is available for the standard species Lemna gibba G3 (inflated duckweed) but little was known to date about the sensitivity of other aquatic plants. In this study, the effect of sulfosulfuron on three common macrophytes was investigated in a static, outdoor, mesocosm experiment. The species tested were two monocotyledons, Glyceria maxima (reed sweet-grass, emergent) and Lagarosiphon major (curly waterweed, submerged), and one dicotyledon, Myriophyllum spicatum (spiked watermilfoil, submerged). The herbicide was applied once at 5 dose levels to ponds containing potted test plants in approximately 230L of water. Plant growth was monitored for up to 70 days by measurement of dry weight (all species), and shoot height and numbers (Glyceria only). At given intervals during the exposure phase, some plants from each pond were transferred to mesocosms containing fresh water. The ability of each species to recover from herbicide exposure was then monitored for 70 days. Data indicates that, at environmentally relevant concentrations, sulfosulfuron does not cause adverse effects in the tested macrophytes. Furthermore, Lemna gibba remains the most sensitive aquatic plant tested and is therefore an appropriate species for use in the risk assessment of this compound. Key words: sulfosulfuron, aquatic plants, mesocosm, recovery |
