Aspergillus candidus

Aspergillus candidus is a fungal species belonging to the kingdom Fungi, phylum Ascomycota, and genus Aspergillus. It is widely recognized as a saprophytic fungus that thrives in stored agricultural products.

The fungus develops a dense, fluffy mycelium. In the early stages of colonization, the mycelial mass is distinctly white, which is the characteristic feature that gave the species its name.

The conidial heads are globose and produce high concentrations of spores. These spores are lightweight and easily dispersed by air currents, making rapid cross-contamination in storage facilities a significant risk.

As a xerophilic fungus, Aspergillus candidus is uniquely adapted to grow in environments with low water activity. This trait allows it to colonize grains and seeds that are too dry for most other common molds.

The species grows optimally at temperatures ranging from +25°C to +30°C. However, its physiological plasticity enables it to survive and proliferate under various environmental stress factors in agricultural settings.

This pathogen causes severe damage to a variety of stored crops, including wheat, barley, maize, rice, and legumes. It is particularly notorious for damaging oilseeds like soybean and sunflower.

The metabolic activity of the fungus releases heat as a byproduct, which leads to the phenomenon known as "hot spots" in grain piles. This self-heating process further accelerates the degradation of the grain mass.

Infected seeds lose their viability, rendering them useless for planting. Furthermore, Aspergillus candidus produces various mycotoxins, which pose significant health risks to both livestock and human consumers.

The enzymes secreted by the fungus break down the starch and proteins within the grain, leading to a significant loss of nutritional value and undesirable changes in flavor and odor.

Advanced stages of infection result in grain caking, where the mass becomes clumped together by thick fungal mycelia, which interferes with standard grain handling and processing machinery.

The most prominent sign is the appearance of a white, powdery fungal growth on the surface of seeds, particularly near the germ area where internal moisture is typically higher.

A sudden rise in grain temperature is a critical indicator of infestation. Temperature monitoring systems often detect abnormal spikes in stored grain long before the mold becomes visible to the naked eye.

Infested storage facilities often exhibit a distinct musty or earthy odor. This olfactory signal is an early warning sign that the fungal population has reached a significant biomass.

Close inspection of the grain may reveal small, dense, white-to-creamy conidial heads covering the surface of individual kernels, indicating active sporulation.

As the infection progresses, the grain surface may become discolored, shifting toward grayish tones as the fungal mycelium colonizes the deeper layers of the seed coat and endosperm.

The primary control strategy involves reducing the moisture content of the grain below 13% during storage, which prevents the fungus from germinating and reproducing effectively.

Maintaining proper hygiene in storage facilities is essential. Regular cleaning of bins, conveyors, and floors removes organic debris that serves as a reservoir for fungal spores.

Active aeration and ventilation are crucial to manage the temperature of the grain mass. Keeping the grain cool significantly slows down the metabolic rate of the fungus and limits its spread.

If necessary, approved fungicidal treatments can be applied to storage areas to ensure that surfaces are free from inoculum before new crops are introduced.

• Effective moisture management during grain drying.
• Regular temperature monitoring to detect hot spots.
• Cleaning grain to remove dust and broken kernels.