Impact of reduced and zero tillage on activity and abundance of slugs in winter oilseed rape

The impact of reduced and zero tillage on activin and abundance of slugs in winter oilseed rape has been investigated in a field trial From autumn 199 5 till autumn 1997. In this trial, non-inversive tillage and direct drillin g were compared with conventional ploughing. Plots were split up in untreat ed and molluscicide-treated with two applications of metaldehyde metaldehyd e (3 kg ha(-1)). Slug activity was monitored by slug mats (refuge traps), a nd slug abundance was assessed by fenced beer traps as well as fenced slug mars (defined area traps). Sampling commenced at drilling in late August an d was carried out for 10 weeks each year. Deroceras agreste, D. reticulatum , Arion distinctus and A. fasciatus were the slug species commonly Found in our field trial. Reduced and especially zero tillage increased activity an d abundance of all species, however, with varying extent in different years . No long-term effect of the molluscicide could be detected, but four of si x applications were Followed by a 2 to 3 week period of lower dug activity in treated plots. Therefore, growers should monitor slug activity using slu g mars or comparable methods near sowing date to be aware of a potential ri sk of slug damage to the crop as early as possible.