Italian Scientists Discover Social Wasps Spread Beneficial Yeasts Crucial for Sustainable Winemaking

Italian researchers have found that social wasps, specifically those from the Polistes and Vespula genera, play a significant role in preserving and spreading yeast species important for winemaking. The study, conducted in three Tuscan wineries—Chianti Classico, Brunello di Montalcino, and Vino Nobile di Montepulciano—focused on identifying the yeast communities present on the exoskeleton and in the gut of wasps, as well as on the surface of grapes collected from these vineyards.

Sampling took place during the grape harvest season. Researchers captured 57 wasps using entomological nets during the warmest hours of the day, when wasp activity peaks. The wasps were then transported to the laboratory under refrigerated conditions to maintain their viability. At the same time, grape samples were collected from each vineyard for comparison.

The analysis revealed that 74% of the captured wasps carried yeasts. Most of these were found in female worker wasps, with yeast concentrations in their guts reaching up to 7 × 10⁵ CFU/mL. Yeasts were less commonly found on the exoskeletons. The identification process, which involved DNA amplification and sequencing, uncovered 20 yeast species from 10 different genera. Two species—Aureobasidium pullulans and Metschnikowia pulcherrima—were consistently isolated from wasps across all three wineries. M. pulcherrima appeared most frequently.

Further genetic analysis showed that some yeast strains present in grapes were also found in the guts of wasps from the same vineyard, indicating a direct transfer between insects and fruit. This supports previous findings that social wasps act as vectors for yeast dispersal in vineyard ecosystems.

The researchers then focused on M. pulcherrima strains due to their known bioprotective properties in winemaking. These strains underwent laboratory tests to assess their ability to inhibit unwanted wine yeasts such as Kloeckera apiculata and Brettanomyces bruxellensis, both associated with spoilage and off-flavors in wine production. Three M. pulcherrima strains demonstrated strong inhibitory effects against these spoilage yeasts.

To test their practical application, scientists artificially contaminated grapes with undesirable yeast species and then treated them with selected M. pulcherrima strains. The results showed a significant reduction in populations of spoilage yeasts on both grapes and must after treatment with M. pulcherrima compared to untreated controls. This suggests that these indigenous yeast strains could serve as effective biocontrol agents during early stages of winemaking, potentially reducing reliance on chemical preservatives like sulfites.

The study also highlighted that environmental factors such as surrounding woodland can influence the diversity of yeasts carried by wasps into vineyards, but certain species like M. pulcherrima are consistently present regardless of location or habitat.

Interest in non-Saccharomyces yeasts like M. pulcherrima is growing within the wine industry due to their potential to enhance wine aroma and provide natural protection against spoilage organisms. Some commercial products based on this yeast are already available internationally.

The findings confirm that social wasps are not only important for maintaining yeast biodiversity in vineyards but also represent a natural reservoir for beneficial yeast strains that can be harnessed for sustainable winemaking practices. The research opens new possibilities for using native insect-associated yeasts as part of integrated pest and microbial management strategies in viticulture.

This work adds to a growing body of evidence showing that insect-driven dispersal is integral to shaping vineyard microbiomes throughout the growing season. By identifying specific yeast strains shared between wasps and grapes, Italian scientists have provided a foundation for future biotechnological applications aimed at improving wine quality while reducing chemical inputs in production.

The study was published open access on November 25, 2025, by Damiano Barbato, Simona Guerrini, Viola Galli, Eleonora Mari, Marzia Cristiana Rosi, and Lisa Granchi. It represents one of the most comprehensive investigations into the role of social wasps as vectors and reservoirs of non-Saccharomyces yeasts relevant to modern oenology.