Aspergillus rot of grapes

The causative agent of this disease is the fungus Aspergillus aculeatus, a member of the black Aspergillus group. It is primarily a facultative pathogen that acts as a secondary invader, infecting plant tissues that have already been compromised by mechanical stress, insect damage, or environmental factors such as heavy rain.

The primary crop affected by this pathogen is the cultivated grapevine. The fungus thrives on ripening berries, particularly as they increase in sugar concentration, making the internal tissues highly susceptible to colonization once the protective epidermal layer is breached or damaged by pests.

Symptoms of the infection include a distinct dark, often black, powdery mold covering the surface of the berries. Affected grapes rapidly lose their structural integrity, becoming mushy and emitting a characteristic moldy or musty odor. As the infection progresses, the berries dehydrate and shrivel, resulting in a condition often described as raisin mold.

Conditions favorable for the development of the fungus include high humidity and warm temperatures during the late stages of ripening. Dissemination of spores occurs through wind dispersal, rain splashes, and insect vectors, particularly vinegar flies (Drosophila), which transport the pathogen from diseased berries to healthy ones.

The economic impact of the disease is significant, as it leads to both direct yield loss and reduced quality of the harvest. The presence of Aspergillus species can contaminate grape must with mycotoxins, which can inhibit natural fermentation processes and negatively affect the sensory profile of the final wine product.

Effective management and prevention strategies include:

• rigorous pest management to prevent skin damage to the berries;
• canopy management practices to ensure optimal air circulation and reduce humidity within the grape clusters;
• prompt removal of infected clusters to reduce the local inoculum load;
• appropriate use of fungicides during the pre-harvest period to protect against opportunistic fungal growth.