Slug population changes following molluscicide treatment in relation to distance from edge of treated area

Abstract

Methiocarb pellets were broadcast in autumn 1987 on to two large plots sown with winter wheat, each 36 m × 36 m, and two similar plots were left untreated. Numbers of slugs were recorded in soil samples and bait traps 2, 4, 8 and 16 m from the edges of plots. Methiocarb treatment initially decreased slug numbers in treated plots by ∼ 70%, but in subsequent months numbers declined also in untreated plots to levels similar to those in treated plots. There was no evidence of significant movement of slugs between plots during this period. It is concluded that a plot size of 6 m × 6 m with a central sampling area of 2 m × 2 m would probably have given the same result as the large plots used in this experiment. Plots of 12 m × 12 m with a central sampling area of 4 m × 4 m should be more than adequate for studies of changes in slug numbers on different treatments throughout a growing season.