South Africa Wine Technical Yearbook 2025

Practice: Harnessing biostimulants and biological control agents Disease pressure and pest outbreaks are expected to rise in the face of climate change. In the pursuit of a more sustainable and ecologically integrated approach to wine growing, RV has embraced the use of biostimulants and biological control agents (BCAs) as natural alternatives to synthetic fertilisers, pesticides and fungicides. Biostimulants are formulations containing natural substances or microorganisms that have the ability to enhance a plant’s ability to absorb nutrients, resist environmental stress, and improve yield and fruit quality. Meanwhile, BCAs are beneficial organisms – such as bacteria, fungi, or insects – that either directly attack pests and pathogens or help activate the plant’s own defence systems. BCAs can help to reduce dependence on synthetic fungicides and pesticides, and in turn reduce the risk of chemical residue in grapes or wine. Addressing vineyard pests and diseases sustainably Grapevines are particularly vulnerable to diseases like downy mildew, historically managed using copper-based fungicides. While effective, copper builds up in vineyard soils over time, disrupting soil biology, reducing root development, and even affecting fermentation due to its impact on yeast. In response, RV is investigating a range of microbial BCAs as safer, more sustainable alternatives. Several bacterial and fungal species have demonstrated efficacy in controlling downy mildew while avoiding the long-term consequences of copper accumulation. However, the success of these BCAs can vary widely between vineyards, depending on factors like soil type and local climate. In some cases, introducing these microbes has even reduced fungal biodiversity in the soil, raising questions about unintended impacts on the soil microbiome. The key challenge moving forward is understanding how BCAs behave in different environments and what long-term effects they may have on the complex biological systems that underpin vineyard health. Vine resilience and growth – promising effects Biostimulants are gaining popularity for their potential to not only enhance a plant’s nutrient status, but also to boost a vine’s resilience to environmental stress, such as drought and salinity. Studies conducted in controlled conditions – such as potted vines in glasshouses and labs – have found that seaweed extracts, arbuscular mycorrhizal fungi (AMF), and silicon-based treatments can enhance grapevine tolerance to water stress by improving root function and photosynthesis. Application of collagen-based biostimulants to grapevine roots, for example, has been shown to help vines better withstand water deficit stress. Similarly, BCAs like Bacillus licheniformis and Pseudomonas fluorescens can prompt the vine to produce protective compounds, including abscisic acid (ABA), helping to reduce water loss through the leaves.

Other BCAs offer a dual benefit: enhancing grapevine resistance to pathogens like Botrytis cinerea (which causes bunch rot) or downy mildew, while simultaneously enhancing plant resistance to water stress or other abiotic stress. However, much of this promising evidence comes from studies in controlled environments. Climate and location are known to significantly affect the impact of biostimulants. Real world, field-based research over multiple growing seasons and in diverse vineyard conditions is still lacking. Enhancing wine quality through natural inputs Beyond pest control and vine health, biostimulants can also influence grape and wine quality. Some function as bio-elicitors, triggering the production of valuable secondary metabolites like anthocyanins (responsible for red grape colour) and stilbenes (linked to antioxidant activity). Applications of natural extracts – such as brown seaweed, protein hydrolysates, commercial yeast extracts and methyl jasmonate – have been shown to increase these secondary metabolites, potentially enhancing the sensory profile of the wine. The role of vineyard biodiversity RV systems strive to support functional biodiversity, not just within the vineyard, but also in the surrounding landscape. Semi-natural habitats such as woodlands and hedgerows can play an important role in boosting the presence and effectiveness of BCAs. For example, birds and parasitic wasps that prey on grapevine moths are more likely to thrive in heterogeneous landscapes, improving natural pest control. This interdependence between vineyard biodiversity and pest management highlights the need for RV systems to consider both in-field practices and landscape-scale strategies to maximise ecological resilience. Paving the next steps Despite promising results, researchers agree that much remains to be learned. There’s a pressing need for long-term field studies examining how different biostimulants and BCAs behave under real vineyard conditions. Key questions include: How stable are these treatments once applied? How long do they remain active? What is the optimal dose, application method and timing? In addition, future studies should explore how combinations of biostimulants, BCAs and cultural practices – such as leaf removal or disease-resistant grape varieties – interact, as well as their effects on soil health and microbial biodiversity. Special attention should also be paid to currently under researched pests and diseases, including nematodes, phytoplasmas, viruses and pathogenic bacteria, which remain significant threats in many wine-growing regions. Ultimately, integrating these biological tools effectively will depend on a deeper understanding of their ecological interactions within the vineyard system. If successful, they could significantly reduce the need for synthetic chemicals. Next month, Part 2 will take a deep dive into cover crops and weed management in RV. 

For more information, contact Anel Andrag at anel@sawine.co.za. Reference https://www.wineland.co.za/rooted-in-research-what-science-says-about-regenerative-viticulture-part-1/

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TECHNICAL YEARBOOK 2025