Aureobasidium pullulans

Aureobasidium pullulans is a ubiquitous fungus often referred to as a black yeast. While it can exist as a saprophyte, in an agricultural context, it is frequently associated with the development of sooty mold on various crops, which can significantly affect the commercial value and appearance of fruits and leaves.

This fungus primarily targets pome and stone fruits, such as apples and pears, as well as grapes and various greenhouse vegetables. It thrives on surfaces enriched with sugars, such as nectar or honeydew secreted by sap-sucking insects, making pest management a critical component of disease control.

The symptoms of infection are characterized by dark, velvety, or slimy spots appearing on the surface of fruit skins and foliage. While the damage is often superficial, the presence of Aureobasidium pullulans can lead to physiological stress in the plant, reduce photosynthetic efficiency, and promote post-harvest decay if left unmanaged.

Environmental conditions play a decisive role in the spread of this pathogen. Warm temperatures, high relative humidity, and the presence of free water on plant surfaces are the primary drivers of spore germination and colony expansion. Dense canopy structures that prevent rapid drying after rainfall are particularly susceptible to heavy colonization.

Effective management and prevention of this fungal infection rely on a combination of cultural and chemical practices:

• Implementing proper pruning techniques to increase light penetration and air circulation.
• Systematic monitoring and control of insect pests that produce honeydew.
• Maintaining strict sanitation protocols by removing infested plant debris.
• Applying fungicides during periods of high humidity if the risk of infection is significant.
• Utilizing biological control agents that compete with the fungus for resources on the leaf surface.