SLUG DAMAGE AND NUMBERS OF SLUGS IN OILSEED RAPE BORDERING ON GRASS STRIPS

In 1995, slug damage and numbers of slugs were estimated in two grass strips and adjacent rape fields. Investigations began as soon as rape seedlings emerged and lasted for five weeks. Slug damage to rape plant s 1 m from the grass strips was significantly higher than at greater d istances from the strips. Deroceras reticulatum was the most abundant slug species recorded in both grass strips and adjacent rape fields. A rion lusitanicus and Arion fasciatus were much less abundant than D. r eticulatum. In one field, D. reticulatum declined steadily with increa sing distance from the grass strips and therefore appeared to have cau sed the majority of severe damage to rape plants close to the strips. This finding was surprising because until now severe slug damage in oi lseed rape beside semi-natural habitats has been observed only where A . lusitanicus was abundant.