WA2 Plant Toxicology and Soil Interactions
Ballroom F, Level 4
8:00 AM - 12:00 PM, Wednesday, 12 November 2003
Chair: Jackson, Andrew ,
(337) Comparative toxicity of clomazone to rice and watergrasses.
TenBrook, P.1, Tjeerdema, R.1, 1 Department of Environmental Toxicology, University of California, Davis, CA, USA
ABSTRACT- Clomazone, 2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone, is expected to be approved for use in California rice agriculture in the near future. However, rice injury has been observed in field tests of this herbicide. Clomazone causes bleaching in plants due to inhibition of beta-carotene synthesis. Seedlings of rice (Oryza sativa) and watergrasses (Echinochloa spp.) were exposed to clomazone for 7 d in a hydroponic system to determine relative sensitivities to clomazone as measured by growth and beta-carotene levels. For rice, the growth NOEC was 1.9 mg/L clomazone and the IC25 was 1.4 mg/L. Watergrass growth NOEC values ranged from 0.05-0.11 mg/L clomazone, while IC25 values ranged from 0.10-0.18 mg/L clomazone. Based on beta-carotene levels, rice had a NOEC of 0.05 mg/L and an IC25 of 0.10 mg/L clomazone, while watergrass NOEC values ranged from < 0.02-0.11 mg/L and IC25 values ranged from 0.02-0.13 mg/L.
Key words: rice, clomazone, Echinochloa spp., toxicity