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.