The rate of damages caused by the field slug Deroceras reticulatum to winter oilseed rape and winter wheat was investigated under field and laboratory conditions. The number and degree of seedling damages were estimated on the basis of the intensity of slug occurrence, which were caught in baited traps. It was found that over a 3-4-week period after sowing, damages caused by D. reticulatum slugs constituted 60% in young oilseed rape and 40% in wheat plants. Under laboratory conditions, one slug damaged almost completely 10 rape seedlings (95%) during 13 days of its feeding. The percentage damage caused by the pest to wheat seedlings was considerably lower (53%), whereas wheat seeds appeared to be severely damaged (83%) after 9 days of the slug feeding.

Studies on food preference of herbivores include no-choice test and test with choice or multiple choice. Conclusions from statistic analyses of these tests are compared descriptively. The definition of compatibility index and consumption growth index has enabled us to use nonparametric test for verification of hypotheses about homogeneity of the consumption growths of selected plant species under no-choice and multiple choice conditions. The studies were conducted on food preference of the slug Deroceras reticulatum. It has been found that Chamaenerion angustifolium, Geraniumpusillum and Potentilla anserina can be used to reduce this slug feeding on cultivated plants. It has been also found that seedlings of Polygonum aviculare can be used as alternative food for slugs.