Food plant preferences by slugs and snails: A simple method to evaluate the relative palatability of the food plants

Abstract

Food plant selection by herbivores is of major importance in relation to plant population dynamics and plant selection in natural ecosystems as well as to crop protection. Slugs and snails are of major importance in this connection, and the proposed method is a valuable tool in the evaluation of their food plant preference. In the test, ten snails or slugs are given the choice between two alternative test plants at the same time. A logarithmic scale from 1 to 5 indicates the eating index, E, and from this figure a preference value, P, is derived by the formula P = El√t×1000, where t is the time in minutes. Using Helix pomatia and Arion ater, a preference scale has been obtained for selected plant species. From this scale it may be deduced that plants containing potent constituents against mammals are readily accepted by land molluscs, whereas plants generally avoided by molluscs are those containing tannins and phenolics.