Introduction

Various strategies have been and are still being explored to manage diseases in viticulture effectively. These include cultural practices, selection of resistant cultivars, chemical control (fungicides and bactericides), and biocontrol. But what do we know about this last strategy, and why is it important for viticulture?

Biocontrol refers to using living organisms, mainly microorganisms called biocontrol agents (BCAs), to manage and reduce pests, diseases, and invasive species. This environmentally friendly approach is an integral part of control strategies and offers an alternative to chemical pesticides, which can negatively affect the environment and human health.1 Different countries’ and regions’ policies aim to reduce synthetic pesticide use and ensure responsible consumption and production, life on land, and clean water.2,3 However, implementing BCAs requires in-depth studies on the complex interactions in plant-microbe-environment interplay. 

Among the characteristics of BCAs is their ability to compete effectively for nutrients and space, which are involved in suppressing pathogen growth. They also produce volatile and non-volatile compounds in a process called antibiosis. Finally, BCAs can directly parasitise pathogens. Nowadays, using BCAs with combined approaches (especially those that operate by different mechanisms of action) is useful because it forces a pathogen to overcome several hurdles instead of just one to establish and develop an infection. Additionally, combinations of approaches may have additive or synergic effects.

How can BCAs be useful?

Using BCAs as a preharvest and postharvest treatment to control diseases caused by pathogens has many advantages:

• They can persist on the fruit surface for an extended period.
• They are generally safer for human health than many chemical agents.
• They are eco-friendly.
• They maintain ecological balance and promote biodiversity.
• They can protect the product from reinfection due to their persistent viability.
• They have a lower potential for pathogens to develop resistance.
• Products treated with BCAs potentially open more export opportunities.2

Finding effective BCAs

In the fight for sustainable disease management, finding effective biological control agents within a diverse microbial landscape – bacteria, yeasts and filamentous fungi – is essential but challenging. Vineyards, which host a remarkable diversity of microbial communities, serve as a natural reservoir of potential BCAs. In vitro assays and in vivo studies are crucial in evaluating their inhibitory activity against target pathogens.4 

However, this search goes beyond finding a single effective agent. The possibility of combining several BCAs should be explored not only to achieve a greater impact but also to reduce the emergence of new resistances. This raises some interesting questions.

Friends or foes?

How do these BCAs interact with each other and with the target pathogen? Will they work together as a team or hinder? If the target pathogen is successfully eliminated, could others take advantage?

Researchers are figuring this out by studying how BCAs interact with each other, with the target pathogen, the host plant and other microorganisms. By unravelling these complex microbial relationships, they are paving the way for a future where we can assemble the ultimate BCA consortium: a powerful, well-coordinated force for sustainable fungal disease control in the vineyard.

How do you unlock the secrets of BCAs?

The widespread adoption of next-generation sequencing (NGS) techniques has revolutionised the field of biocontrol. These techniques, which include whole genome sequencing, transcriptomics, proteomics and metabolomics, allow the identification of the molecular pathways and essential genes that play key roles in biocontrol.5 

Have any BCAs been approved?

Yes, but despite their growing potential, BCAs currently represent a small fraction (1%) of the agricultural control market compared to the dominance of synthetic pesticides (15%) 6. This limited adoption can be attributed to several factors: 

• Efficacy: Sometimes, BCAs may not provide the same level of immediate and predictable disease control as synthetic fungicides. 
• Knowledge gap: Commercialising biopesticides often involves proprietary formulations, limiting publicly available information on successful production and application methods. 
• Registration and patenting: This can be complex and time-consuming, particularly in certain regions (e.g., Europe).  
• Farmer adoption: Financial incentives for farmers to switch from conventional fungicides to BCAs might be limited, especially if they are unaware of and have no experience with this approach. 7  

Challenges aside, there is a strong trend to use microbial biocontrol agents for plant disease management. Therefore, research in this field is expected to continue to attract increasing attention, opening new highways toward an environmentally sustainable future.