Occurrence of earwigs in vineyards and their impact on aroma and flavourof 'Chasselas' and 'Pinot Noir' wines
Abstract: The European earwig Forficula auricularia L. (Dermaptera, Forficulidae) is anomnivorous predator that is considered a beneficial insect. In vineyards it preys on pests such asgrape berry moth and other tortricids. Over the last few years earwig abundance increasedoccasionally to levels that were no longer tolerated by European winegrowers since they mayerode berries, transfer fungi spores and contaminate grape clusters with their faeces. Moreover,they are suspected of affecting aroma and flavour of wines. In this study we surveyed thepopulation dynamics of F. auricularia in four commercial vineyards, and we artificiallycontaminated grapes with adults and their faeces.In May, earwig nymphs started to colonise grapevines and the first adults were observed atthe beginning of June. The abundance of earwigs on grapevines and within grape clusters reachedtheir peak in the middle of summer. Although the population density was comparable amongvineyards, more individuals were observed in the tighter ‘Pinot noir’ clusters than in the looser’Chasselas’ clusters. The local environment seemed to have only a minor influence on theabundance of earwigs.The sensory evaluation revealed that 0.6g of earwig faeces per kilogram of ‘Chasselas’grapes had a negative impact on the quality of the corresponding wines. Contaminated wineswere less fruity and less floral, and their aroma was described as faecal. Generally, the wineswere judged to be of lower quality. However, the addition of four living adults per kilogram ofgrapes affected the sensory characteristics of ‘Chasselas’ wines only marginally. Thecontamination of ‘Pinot noir’ grapes with four different levels of living earwig adults showed thatthe corresponding wines smelled and tasted significantly different than the uncontaminatedcontrol wines when ten or more earwigs per kilogram of grapes were used. Contaminated ‘Pinotnoir’ wines were described as “animal”, “reductive”, “vegetal”, “acidic”, “bitter” and “tannic”and were of lower quality.In conclusion, our results show that earwig faeces and adult levels of ten or moreindividuals per kilogram of grapes negatively influence aroma and flavour of ‘Chasselas’ and’Pinot noir’ wines. Winegrowers should therefore monitor the development of F. auriculariapopulations in their vineyards in order to avoid the production of poor wines.