SLUG DAMAGE AND NUMBER OF SLUGS (GASTROPODA: PULMONATA) IN WINTER WHEAT IN FIELDS WITH SOWN WILDFLOWER STRIPS

Abstract

Previous observations have shown that slugs found favourable conditions for reproduction in wildfiower strips and that they caused high damage to oilseed rape adjacent to the strips. In the current study slug numbers and damage were estimated in wildfiower strips and at different distances from the strips into winter wheat crops, from 1994 to 1996. Slug damage was estimated using an index of defoliation and slug numbers and activity were measured using wheat bran traps. Investigations began when winter wheat seedlings emerged and lasted for five weeks. Slug damage was never severe in any of the fields studied. In most fields, slug damage was higher close to the wildfiower strips than at greater distances from the strips. The declining slug damage with increasing distances from the wildflowers strips was related to the distribution pattern of juvenile Arion lusitanicus, suggesting that this species was responsible for the higher damage near the strips. Other slug species (Deroceras reticulatum, Arion fasciatus, Deroceras laeve) were more or less evenly distributed over the field or were almost entirely confined to the wildflower strips. Results showed that winter wheat was not at risk from slug feeding in spite of the establishment of wildfiower strips and that therefore the application of molluscicide along the strips is unnecessary.