Using the copse snail Arianta arbustorum (Linnaeus) to detect repellent compounds and the quality of wood vinegar

Wood vinegar is the aqueous phase of the liquid produced during the slow pyrolysis of wood. It has the potential to be used as a pesticide against various weeds, insects and molluscs. Due to divergent feedstocks, pyrolysis processes and storing conditions, the chemical composition of wood vinegar varies between producers and time. The aim of our current study was to use the copse snail Arianta arbustorum (Linnaeus) as a biological odour detector to identify the effective compounds behind the repellent effect of wood vinegar. We also studied whether variation in the chemical composition of wood vinegars from different producers impacts repellency efficiency. Of the tested constituents, acetic acid, furfural and ether-soluble (mainly aldehydes, ketones, lignin monomers) and ether-insoluble ("wood syrup") fractions of the water extract of wood vinegar induced a clear repellent effect on snails, but their effects were considerably lower than the effect of wood vinegar. Thus the repellent effect of wood vinegar is due to a larger set of its chemical constituents rather than to a specific compound. All tested wood vinegars induced a clear repellent influence on snails, but differences existed between the products of different retorts. These differences were at least partly due to differences in the products' organic material content. According to our studies, A. arbustorum can sense quality differences between wood vinegars, even below 10% dilutions. We suggest that utilizing the avoidance behaviour of A. arbustorum is an easy, non-costly method for monitoring the quality of slow pyrolysis liquids but also hitherto unknown environmental contaminants.