Vineyard Magazine is delighted to welcome Mark Crumpton as a guest writer. In the coming months Mark will cover a range of topics relating to both the vineyard and the winery.  

When moving house recently, I came across my old botany books. One stood out – a 1967 copy of The Biology of Fungi by C.T. Ingold. Flicking through its pages, the hand-drawn schematics of fungal life stages reminded me just how central these organisms are to viticulture and winemaking. 

These simple yet elegant illustrations revealed the complex systems fungi use to grow, reproduce, and interact with their environments. It brought to mind the physicist Richard Feynman, whose famous quote, “There’s plenty of room at the bottom,” speaks to the hidden yet powerful role of the microscopic world. In vineyards, fungi operate largely unseen, influencing nearly every aspect of vine biology and wine quality. Understanding and managing them is key to sustainable grape production and quality winemaking.

Fungi play a crucial yet often underestimated role in viticulture, especially within the UK’s cool, damp climate. While some fungi can cause devastating diseases, others are essential to soil health and fermentation. Balancing this dual role is critical for effective vineyard management.

What are fungi?

Fungi represent a distinct kingdom of life, separate from plants, animals, and bacteria. Unlike bacteria, fungi have defined nuclei and feed by decomposing organic material rather than photosynthesis. In vineyards, fungi are omnipresent, inhabiting soil, leaves, grape skins, and vine tissues, often studied using advanced techniques like radioactive tracing.

Problem fungi in vineyards

Three fungal diseases pose particular concern for UK growers:

  • Powdery Mildew (Erysiphe necator): Appears as a white powder on leaves and berries, reducing photosynthesis, delaying ripening, and impacting wine quality. Traditional sulphur-based fungicides remain effective; however, modern alternatives like potassium bicarbonate and the biocontrol bacterium Bacillus subtilis (which activates the plant’s natural defence mechanisms) are increasingly used. Effective management includes open canopy techniques, precision viticulture for optimised spray timing, grape sorting, and cold soaking to mitigate quality loss during winemaking.
  • Downy Mildew (Plasmopara viticola): This water-loving oomycete fungus causes yellow oil spots on leaf surfaces and a white fungal growth underneath. It spreads rapidly in wet, humid conditions. While copper sprays remain highly effective, their environmental impact has led to increased adoption of biocontrol methods. Additional viticultural practices include early-season shoot removal, improved drainage, trellising for airflow, and weather-based forecasting.
  • Botrytis (Botrytis cinerea): Known primarily for causing bunch rot, Botrytis poses a significant threat to grape quality in the UK’s humid climate. While it can beneficially produce noble rot for sweet wines, uncontrolled infections result in extensive fruit rot. Preventative measures include meticulous canopy management, targeted botryticide applications, and biological sprays. Winemaking adjustments, such as using sacrificial tannins, can mitigate the oxidative impact of the enzyme laccase, produced by Botrytis. Additionally, Botrytis produces β-glucan, a glucose polymer causing haze and clogging, which can be managed using specific enzymes and careful filtration techniques.

Helpful fungi

  • Mycorrhizal Fungi: These beneficial fungi live symbiotically with vine roots, enhancing water and nutrient absorption and reducing plant stress. Their extensive fungal networks significantly improve soil and vine health. Advances in affordable DNA sequencing are deepening our understanding of their importance. Current research strongly indicates that minimising soil disturbance and chemical inputs, especially copper, preserves their beneficial effects.
  • Wild and selected yeasts: Fundamental to winemaking, yeasts are single-cell fungi naturally present on grape skins, becoming active once sugars become accessible. Indigenous yeasts (and bacteria) initiate “fermentation”, contributing unique aromatic complexity. While Saccharomyces cerevisiae typically completes alcoholic fermentation, growing research on non-Saccharomyces yeasts has enabled their commercialisation to enhance wine quality and reduce chemical interventions. Examples include Torulaspora delbrueckii, which enhances aroma and mouthfeel, and Metschnikowia pulcherrima, increasingly used as a biocontrol agent sprayed in vineyards and during harvest to outcompete undesirable microbes.

New and emerging fungal concerns

  • Trunk diseases: Fungi like Eutypa lata and Phaeomoniella chlamydospora infect vine trunks, causing gradual vine decline and eventual death. Recent research highlights the effectiveness of cultural practices such as double pruning, wound protection with biological agents like Trichoderma species, and chemical applications like thiophanate-methyl. Genetic studies also aim to breed vine cultivars with enhanced resistance.
  • Black Rot (Guignardia bidwellii): Previously rare in the UK, its incidence is increasing due to warmer, wetter climatic conditions. New research focuses on improved identification, rapid diagnostics, and disease forecasting models that enable targeted fungicide application. The exploration of resistant grape varieties and precision viticulture techniques are additional proactive measures being developed.

Biological controls and soil health

Fungi themselves can help manage vineyard diseases. Products containing Trichoderma species protect pruning wounds and suppress pathogenic fungi. Additional biocontrol agents, including bacterial sprays and nematodes, further support soil balance and overall vine health.

Conclusion

Fungi are complex yet vital members of vineyard ecosystems. Despite their potential to cause significant diseases, many fungal species actively promote plant growth, soil health, and wine quality. Enhanced understanding and management strategies can help UK growers build resilient vineyards, improve wine quality, and reduce chemical inputs sustainably. As technological advances and science progress it is fascinating to think what more there is to learn in this hidden world.

Humans and fungi: close relatives

  • Humans and fungi share a more recent common ancestor than either does with plants.
  • Both store energy as glycogen (unlike plants which use starch).
  • Fungi and animals belong to the same eukaryotic supergroup: Opisthokonta.
  • This close relationship explains why some antifungal treatments can be difficult as fungal cells resemble animal cells more than bacterial ones.

Understanding this ancient kinship reminds us that when we manage fungi in the vineyard, we’re engaging with a kingdom surprisingly close to our own on the tree of life!


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