Evaluation of palatability of 20 plant species as a food source for slugs Deroceras reticulatum (Mi.iller), Arion lusitanicus (Mabille) and Arion ruf us (Linnaeus) was performed under laboratory conditions in tests with multiple choices and without choice. Rate and degree of damage of seedlings and leaves of matured plants of herbs and winter oilseed rape were calculated. Based on conducted experiments, plant species preferred and rejected by particular slug species were defined. Plants that were preferred by all examined slug species were the following: Brassica napus, Conium maculatum and Lamium amplexicaule. Rejected plants were Polygonum nodosum and Plantago lanceolata. Slugs have showed differentiated preferences towards the remaining plant species.

The intensity of Arion lusitanicus occurrence and the damage degree of 31 crop species have been estimated. It has been found that the slug damaged lettuce and cabbage plants very heavily (Lactuca sativa L. var. capitata L., Brassica oleracea L. var. capitata L. f. alba) and many species of other vegetables (Cucumis sativus L., Phaseolus vulgaris L., Raphanus sativus L. subvar. radicula Pers.). Plant damages in the edge strips were also observed on rape and barley plantations attacked by this slug. The moving activity of particular individuals of Arion lusitanicus was varying. Planning of the experiments in a nested block design has made it possible to statistically determine tendencies of the slug movement. It was observed that when some individuals remained at the point where they were initially placed, others, 2 hours after, moved over 7 m away. The mean weighed length of pathway covered by a single individual and the mean movement rate of one were estimated for each of 9 observation dates. It has been found that slugs penetrating the site surface under observation displayed their tendencies to move towards more moist places and towards food sources.

Studies on palatability of some commom weed species, herbaceous plants and oilseed rape to D. reticulatum, A. lusitanicus and A. rufus slugs have been carried out under laboratory conditions. In food choice trials the rate and degree of damage to seedlings and leaf disks were determined for 20 plant species. The conducted experiments have also permitted to establish, which plant species were preferred or were not accepted by particular slug species. It was found that the studied slug species preferred seedlings and leaves of Brassica napus and Papaver rhoeas, but showed no preference for Epilobium hirsutum, Geranium sanguineum and Saponaria officinalis plants. As to the remaining plant species under study, the preferences exhibited by particular slug species were quite diverse.

Population studies on Arion lusitanicus, a slug species introduced into Poland, were carried out over the last decade. The slug occurs commonly in some areas and spreads out relatively quickly. It has an annual life cycle with eggs, and immature individuals overwinter. In the end of July A. lusitanicus begins copulation and three weeks later it lays eggs from which the first offspring hatch within a month. The copulation process and egg laying last until late fall. One A. lusitanicus can lay over 400 eggs. During the growing season there are two peaks of population density. This species feeds on plant material such as leaves, stems, bulbs, but also consumes animal material. The basic plant material are arable crops particularly vegetables and some species of agricultural crops, some fruit trees, ornamental plants, herbs and weeds. A. lusitanicus displays apparent food specialization and prefers certain cultivated and wild growing plants. A. lusitanicus shows large reproduction potential, wide food and ecologic tolerance, and is regarded as a serious pests occurring in home gardens.