Grey mould pseudocinerea

This pathogen survives in the soil and on crop debris by forming small, black resting structures known as sclerotia. These structures serve as the primary inoculum source for new infections at the beginning of each growing season.

The fungus has a broad host range, infecting various crops including grapes, tomatoes, strawberries, beans, and many ornamental species. Its ability to produce abundant conidia allows it to spread rapidly across fields and greenhouses.

The fungus colonizes plant tissue by secreting enzymes that degrade cell walls, leading to rapid tissue death. This process results in the typical grey, fuzzy mycelium and sporulation that characterize the disease on the surface of the plant.

The epidemiology of B. pseudocinerea is of high concern due to its potential to develop resistance to specific fungicides, making it a challenging target for integrated pest management programs.

Initial symptoms of Botrytis pseudocinerea infection appear as dark, water-soaked spots on leaves, stems, or fruits. As the disease advances, these lesions expand rapidly, turning brown and necrotic.

A diagnostic hallmark is the formation of a dense, grey to ash-colored mold layer on infected surfaces. In high humidity, this layer becomes thick, covering large areas of the plant tissue within a few days.

When fruit is infected, such as in strawberries or tomatoes, the pathogen causes soft, mushy decay. The fruits lose their structure, lose all commercial value, and often become completely unmarketable.

Stem infections can cause girdling, leading to wilting and death of the plant parts above the infection point. In young seedlings, this often results in damping-off, causing total loss in nursery settings.

In grapes, the fungus often attacks inflorescences and stalks, causing them to wither and dry out. This can lead to significant yield reduction and poor-quality grape clusters that are highly susceptible to further microbial decay.

The optimal environment for the development of grey mould pseudocinerea includes moderate temperatures between 15–22°C and high relative humidity, typically above 80–90%.

The presence of free moisture (dew, rain, or irrigation drops) on plant surfaces is essential for spore germination. This makes rainy and foggy weather the most dangerous periods for rapid disease expansion.

Dense planting patterns and poor air circulation in greenhouses create microclimates that trap humidity, allowing the fungus to thrive. Under these conditions, the infection cycle can repeat in very short intervals.

Physical wounds on the plants, whether from insect feeding, hail damage, or improper pruning, provide immediate access points for the fungal spores to infect the plant tissue.

Lack of sanitation in the field or greenhouse allows sclerotia to persist for long periods. If dead plant matter is not removed, it acts as a constant reservoir for the pathogen to re-infect healthy crops in the subsequent year.

The primary harm caused by Botrytis pseudocinerea is the direct destruction of yield, which can exceed 50% in severe outbreaks. The speed of decay often leaves little time for producers to take corrective actions.

Post-harvest losses are equally significant, as seemingly healthy fruits may already be infected with latent inoculum. This leads to massive spoilage during storage and transit, ruining entire shipments of produce.

Infection compromises plant vigor, making them more susceptible to other stress factors or secondary bacterial pathogens. This forces farmers to implement more intensive and expensive pesticide programs.

Marketability is severely impacted, as infected produce cannot meet quality standards for supermarkets or fresh markets. Furthermore, the presence of fungal toxins can raise food safety concerns, limiting processing options.

For nurseries, this disease can lead to the total loss of young stock. The cost of replacing failed crops and the investment in soil remediation after a severe outbreak place a heavy burden on the agricultural enterprise.

Successful management of Botrytis pseudocinerea relies on an integrated pest management (IPM) approach that combines cultural practices, biological tools, and targeted chemical applications.

Sanitation is the most important cultural practice. Removing and destroying all infected plant material promptly reduces the local spore population and limits the spread within the field.

• Maintaining proper plant spacing to improve airflow.
• Controlling weeds to prevent them from acting as disease reservoirs.
• Using drip irrigation to keep foliage dry.
• Monitoring environmental conditions and using ventilation to control humidity.

Chemical control should be executed with caution, focusing on rotating fungicide modes of action to manage the risk of resistance development. Always check local regulations and resistance management guidelines.

Biological control agents, such as beneficial bacteria (e.g., Bacillus species), can be effective when applied preventively. These tools support sustainable farming goals while providing a protective barrier against initial fungal colonization.