Acetic acid bacteria

The causal agent of this condition is the bacterium Acetobacter aceti, an aerobic gram-negative microorganism. In an agricultural context, these bacteria are known for their ability to convert ethanol into acetic acid, causing significant degradation of plant tissues. They typically act as opportunistic pathogens that thrive in environments where plant surfaces have already been compromised.

The bacteria primarily affect sugar-rich crops, including grapes, apples, pears, and various stone fruits. They tend to colonize fruits that have sustained physical injuries, such as hail damage, cracks, or punctures caused by insect feeding. Because the bacteria require an initial fermentation process, fruits that have begun to degrade due to over-ripeness are highly susceptible.

The primary symptom of an Acetobacter aceti infection is a distinct, sharp vinegary smell emanating from the affected fruits. Visually, the tissue becomes soft, mushy, and often discolored. Unlike many fungal infections, there may be little to no surface growth, as the primary damage occurs internally through the rapid acidification of the fruit cells.

Conditions favorable for the development of these bacteria include temperatures ranging from +20°C to +30°C and high relative humidity. The spread of the pathogen is largely driven by fruit flies (Drosophila), which act as vectors, transporting the bacteria between decaying and healthy fruits. Additionally, contaminated harvesting tools and debris can contribute to local outbreaks in orchards.

The economic impact of this bacterium is significant, as it leads to total post-harvest loss. Infected produce is rendered unsuitable for fresh market sale or industrial processing due to the altered chemistry. Preventive measures focus on integrated pest management to reduce fruit damage, maintaining strict sanitation in orchards and storage facilities, and ensuring rapid cooling of harvested crops to inhibit bacterial metabolism.