Baker's yeast

Saccharomyces cerevisiae, commonly known as baker's or brewer's yeast, acts as an opportunistic pathogen in agriculture. While it does not typically invade healthy plant tissues, it effectively exploits wounds and physiological injuries to colonize fruits and succulent plant parts, leading to rapid degradation.

The causal agent is a single-celled fungus belonging to the Ascomycota division. It functions as a fermentative saprotroph, metabolizing simple sugars found in the plant sap. This metabolic activity leads to the rapid breakdown of plant cellular integrity and the release of fermentation byproducts.

Various sugar-rich crops are susceptible to this infection, particularly grapes, strawberries, raspberries, and stone fruits. Vulnerability is highest during the ripening stage, especially when environmental conditions or insect activity compromise the protective outer skin of the fruit.

Symptoms of infestation include localized softening of the tissue, the emergence of a sharp, acidic fermentation odor, and the presence of small gas bubbles on the surface. Affected areas quickly develop a light-colored film of yeast cells, rendering the produce unmarketable and susceptible to further rot.

The spread of this yeast is significantly enhanced by high humidity, ambient warmth, and the presence of pre-existing micro-injuries. Effective protection involves integrated pest management to prevent skin damage, harvesting fruits at the correct maturity level, maintaining proper post-harvest refrigeration, and sanitizing storage facilities to minimize the spore load in the environment.