Influence of aromatic substances on locomotor activity of Deroceras agreste slugs

Abstract

The global climate changes are causing an increase in the number and harmfulness of slugs. Deroceras agreste (Linnaeus, 1758) (Stylommatophora, Agriolimacidae) is a polyphagous phytophage that damages over 150 species of plants, including many vegetables, cultivated berries and grasses. Other than decrease in yield, slugs cause deterioration of consumer qualities of the products, promote infections of plants, and are intermediate hosts of some parasites of mammals and birds. Thus, slugs impose great losses on agricultural farming, and therefore the objective of our study was determining the variability of locomotor activity of D. agreste slugs in reaction to aromatic substances. We determined repellent or attractive effects of those substances for the purpose of further using the obtained data for plant protection. We tested 52 substances and their mixtures, which were conditionally divided into the following groups: chemical solvents, plant extracts, aromatizers, organic acids and synthetic cosmetic additives. Only dimethyl sulfoxide could be identified as an attractant. All the rest of the substances increased the speed of the slugs to various degrees, but had no significant effect on the direction of the animals’ movement. Gasoline increased the speed of the slugs’ movement by 3.20 times, xylene by 4.56. The most effective organic acids and aromatizers to increase the moving speed of slugs were avobenzone and formic acid: the first caused a 2.83-fold increase in the moving speed, the other a 3.16-fold increase. Only one of 13 aromatic substances changed the direction of the slugs’ movement during the experiment – β-ionone. As with the plant extracts, the highest effect on locomotor activity of slugs was exerted by tree bark of Quillaja saponaria (3.64-fold) and Aesculus hippocastanum extract (4.33-fold). Furthermore, together with Capsicum frutescens, they changed the direction the mollusks were moving in, and therefore could be used as repellents. Synthetic cosmetic additives hydrolyzed silk and chrysalide oil exerted the greatest effects on the lcomotor activity of slugs (3.16 and 3.20 times, respectively). A total of 78.6% of the slugs moved away from chrysalide oil, and thus this oil may be suggested as a repellent, as well as mousse de babassu and cocamidopropyl betaine (84.6% and 78.6%, respectively). Therefore, a large amount of the tested substances to one or another extent made the slugs move faster, but most of them did not alter the direction in which the slugs were moving.