METOLACHLOR, S-METOLACHLOR AND THEIR ROLE WITHIN SUSTAINABLE WEED-MANAGEMENT

The herbicide metolachlor has been widely used for over 20 years for s elective weed control in more than 70 crops worldwide. Its favourable soil behaviour and low risk for developing weed resistance means that metolachlor integrates well into sustainable weed-management practices , such as conservation tillage. Metolachlor consists of four stereoiso mers, with herbicidal activity coming mainly from the S-isomer pair. A new catalyst system developed allows the commercial production of ena ntiomerically-enriched S-metolachlor (ISO draft common name). In field trials carried out 1995-1996 S-metolachlor demonstrated equivalent ef ficacy on major grass weeds and tolerance to different maize cultivars at 65% the use rate of metolachlor. In laboratory studies in differen t soils degradation half-lives were similar for metolachlor and S-meto lachlor. The mean half life of S-metolachlor was 23 days in dissipatio n studies at different European field sites. At the lower use rates an d with highly concentrated formulations containing up to 96% (w/v) act ive ingredient, the use of S-metolachlor will result in a substantial reduction of risk to applicators, consumers and the environment and th e herbicide will continue to play an important role in sustainable wee d-management. (C) 1998 Elsevier Science Ltd. All rights reserved.