Evaluation of the risk related to Halyomorpha halys in the Libournais wine region

Abstract: The presence of the invasive stink bug species Halyomorpha halys in the Bordeaux
vineyards since 2020 has raised concerns among wine growers in the Pomerol and SaintEmilion AOC regions. These production areas are characterised by manual harvesting and the production of high value-added wines, whose quality is likely to be altered by the aromatic deviations generated by the presence of harvested insects. To evaluate the risk faced for these wine-growing areas, we monitored the abundance of H. halys nymphs and adults in selected vineyards. Monitoring was carried out in 2021 on a few plots (n = 5) using the beating technique for 20 vines per plot every two weeks from the beginning of the vegetative phase of vines in April to the end of harvest in September. It showed that H. halys was present in the vineyard plots, that at least one generation was occurring on grapevines and that adults were detected on vines as soon as fruit set was reached, followed by nymphs from the bunch closure stage. In 2022, a much comprehensive sampling (n = 26) was conducted to characterise the abundance of the insect, taking into account the type of landscape surrounding vineyard plots. Five beating sessions of 20 vines per plot on a monthly schedule were carried out from before fruit set to maturation. We found that 92 % of the plots were infested. Halyomorpha halys individuals were detected earlier and in higher abundance in plots surrounded by semi-natural habitats, with significantly higher abundances of nymphs. At harvest, the assessment of three transport crates for each of the 12 plots (several hundred bunches depending on the crates) showed a very low level of infestation per bunch: on average, H. halys were detected in 2 % of bunches during the manual harvesting operation. After transport, when the harvest was being received in the winery, the rate of infestation of these same bunches decreased to less than 1 %. Finally, in the winery, after the bunch processing line, no insect was observed in the optical sorting machine before these bunches were put into the fermentation tank. These observations indicate that the current population levels of H. halys may probably pose no considerable risk to the wine quality in the Pomerol and Saint-Emilion AOCs. However, this study only applies to this area of manual harvesting and cannot be extrapolated to mechanical harvesting, which is characterised by other equipment in the winery. An assessment of the risks for mechanical harvesting should
therefore be conducted. Despite the findings of this survey, the quantitative evolution of
populations should be monitored to anticipate any new outbreaks of this invasive insect recently arrived in the Bordeaux region.