Top 5 Diseases in Vineyards in California

Soil diseases can significantly impact crop productivity and quality, with certain diseases posing a particular threat to vineyards in California. In 2023, BeCrop® technology identified several top soil borne bacterial and fungal diseases affecting vineyards in California. This article will provide valuable insights for vineyard owners and growers in the state, helping them make informed decisions to protect their vineyards from these prevalent diseases.

The top 5 diseases affecting vineyards include Pierce's Disease, Powdery Mildew, Botrytis Bunch Rot, Esca Complex/Petri, and Blackfoot. 

These diseases pose a significant threat to vineyards and can vary in impact based on the region and climate. Understanding the microbial communities in vineyards and their impact on disease development is crucial for effective disease management and sustainable grape production.

How Microbial Communities Impact and Help Prevent Disease Development 

Microbial diseases in vineyards can negatively impact grapevine health and overall wine quality. They originate from various pathogens, including bacteria and fungi, which can enter the vineyard via soil, wind, insect vectors, or infected planting material. Microbial communities play a crucial role in the prevention of these diseases but can also contribute to the development and spread of them in vineyards. 

Beneficial microbes can contribute to plant growth promotion, disease resistance, and overall vine health, highlighting the importance of maintaining a balanced microbial community in vineyards. Factors such as vineyard location, environment, grapevine cultivar, and management practices influence microbial diversity within vineyards, ultimately impacting wine characteristics, but also the overall health of the crop.

On the other hand, several bacterial pathogens can cause leaf spots, stem rots, root rots, galls, wilts, blights, and cankers in vines, highlighting the importance of managing vineyard diseases caused by harmful bacteria. For landowners looking to mitigate the risks of diseases caused by such pathogens, leveraging biological management solutions and soil microbiome analysis and research can prove beneficial.

As an example, pathogenic bacterial and fungal pathogens colonizing vineyard soil can lead to trunk diseases that affect grapevines' health and longevity, emphasizing the need for effective disease prevention and control measures. The spread of disease can be prevented by understanding how microbe communities work together to maintain aspects like soil health and maintain a healthy microbial population with minimal soilborne pathogen impacts. 

The top 5 diseases Affecting Vineyards

California is a world-renowned wine-growing region, so crop health should always be a top priority for vine growers and winemakers. Some of the top diseases to look out for include:

• Pierce’s Disease: Caused by the bacterium Xylella fastidiosa, this disease is transmitted by xylem-feeding insects and can lead to leaf scorch, defoliation, and ultimately, the death of the vine.
• Powdery Mildew: A common fungal disease caused by Erysiphe necator, leading to a white powdery growth on leaves and berries, ultimately affecting fruit quality.
• Blackfoot Disease: Caused by several species of the Phaeomoniella genus, this disease affects the vascular system of grapevines, leading to wood necrosis and reduced vine vigor.
• Botrytis Bunch Rot: Caused by the fungus Botrytis cinerea, this disease affects grapes, leading to gray mold and berries rotting, particularly in humid conditions.
• Esca Complex/Petri Disease: These are caused by fungi, including Phaeomoniella chlamydospora and Phaeoacremonium spp., leading to the decline of vines and the development of characteristic wood necrosis.

Controlling Bacterial and Fungal Diseases in Vineyards

The following pertains to specific control and preventative measures farmers can take when dealing with these diseases.

Pierce's Disease

Controlling Pierce's Disease, caused by the bacterium Xylella fastidiosa, involves two primary approaches including the following methods. Planting grapevine varieties resistant to Pierce's Disease helps mitigate its impact. For instance, the 'Tempranillo' variety has demonstrated considerable tolerance to the disease.

Managing the population of xylem-feeding insects, such as sharpshooters and spittlebugs, which transmit the bacterium, can effectively control disease. Implementing Integrated Pest Management (IPM) tactics, such as biological control agents, can help keep vector populations in check.

Powdery Mildew

This common fungal disease, caused by Erysiphe necator, can be controlled through Fungicide application which is the regular application of fungicides, especially during the growing season. This can help control the disease by selecting appropriate fungicides and applying them according to label instructions. This is a vital step to minimize the risk of developing resistance among the pathogen populations.

Additionally, proper canopy management and airflow within the vineyard can reduce the humidity that favors powdery mildew growth. Ensuring adequate ventilation and avoiding excessive foliage density can help limit the disease's spread.

Botrytis Bunch Rot

Botrytis bunch rot, a fungal disease caused by Botrytis cinerea, can be managed through a combination of sanitation and canopy management practices. Sanitation involves removing and destroying infected plant material, such as mummified berries, to reduce the spread of the disease. Prompt removal and proper disposal of affected clusters are crucial in preventing further infection. Canopy management focuses on improving airflow and reducing humidity within the plant canopy, creating less favorable conditions for the pathogen. Pruning and trellising techniques that promote good air circulation and drainage are essential aspects of this approach.

Biofungicide products are becoming increasingly prevalent in the agricultural biostimulant market, and some are labeled for the treatment of pathogens like Botrytis. Biofungicides composed of beneficial microbial species or natural fungicidal compounds can reduce disease levels while mitigating harm to the rest of the beneficial microbes present.

Esca Complex/Petri Disease and Blackfoot Disease

While Esca Complex/Petri Disease and Blackfoot Disease pose challenges, control is possible through a multi-faceted approach. Prevention begins with protecting pruning wounds using fungicides or natural antimicrobials and securing certified disease-free vines. Ongoing vine health is crucial, achieved through practices like stress management and vigilant monitoring for early detection and removal of infected plant material. Remember, proactive management, though not a cure, significantly slows disease progression and protects your vineyard's health and yield.

By utilizing these eight strategies in conjunction, vineyard owners and managers can effectively manage and reduce the impact of bacterial and fungal diseases in their vineyards. An integrated approach combining both chemical and nonchemical interventions offers the best chance of success in combating these destructive pathogens.

BeCrop® Biological Soil Analysis For Disease Treatment and Prevention

BeCrop biological soil analysis is a valuable tool for vineyard owners and winemakers, offering a data-driven approach to disease prevention, soil health management, and sustainable agricultural practices. By utilizing the insights gained from BeCrop analyses, stakeholders in the wine industry can make informed decisions to optimize vineyard productivity while promoting environmental stewardship and long-term sustainability. 

For example, one vine-grower in Napa Valley, struggling with declining crop health and low productivity despite heavy investment in disease control, turned to the BeCrop® Test for insights. The test revealed poor biological soil quality and identified a single disease risk, likely exacerbated by excessive use of crop protection chemicals. Following recommendations from Biome Makers agronomists to adjust and reduce crop protection inputs, the grower was able to customize his approach to meet the soil's specific needs, significantly improving vineyard sustainability and achieving a remarkable +170% return on investment.

The BeCrop® Test can help you take preventative measures by identifying soil-born diseases before they take root. 

See below a sample report where several diseases above were detected early from a single soil sample.

Note: Biome Makers agronomists have identified some of the top soil borne bacterial and fungal diseases affecting crops in the US. These diseases are mentioned in the soil. While not all soilborne diseases are included, the selected ones are among some of the most impactful, with variability by region. It's important to note that the diseases are not listed in order of impact, and they do not include viruses. The detection of these diseases is made possible by BeCrop technology and soil database, offering valuable insights for crop management and disease prevention.