Aspergillus parasiticus

Aspergillus parasiticus is a soil-borne fungus that acts as a significant plant pathogen, primarily known for causing seed and fruit decay. This fungus is notorious in agriculture not only for its destructive effect on plant tissues but also for its ability to produce potent secondary metabolites known as aflatoxins, which are highly toxic carcinogens that render agricultural products unsafe for human and animal consumption.

The fungus affects a wide range of crops, with a particular affinity for oilseeds and cereals. Major susceptible hosts include peanuts, corn, cotton, soybeans, and various tree nuts. Infection can occur both in the field, often triggered by drought stress and high temperatures during the growing season, and during post-harvest storage where humidity control is inadequate.

Symptoms of infection are characterized by the appearance of a distinct yellow-green or olive-colored powdery coating on the surface of seeds or kernels. As the infection progresses, the fungal mycelium colonizes the interior of the seeds, leading to tissue degradation, discoloration, and a characteristic musty odor. In advanced stages, the seeds become brittle and lose their viability entirely.

Environmental conditions play a critical role in the development of the disease. Aspergillus parasiticus thrives in warm conditions, with an optimal temperature range of +25°C to +35°C, and requires high relative humidity to initiate and sustain sporulation. The fungus is highly resilient, and its spores can remain dormant in soil or debris for extended periods until environmental conditions become favorable for germination.

Management and prevention strategies focus on preventing colonization and minimizing toxin accumulation:

• harvesting crops at full maturity and drying them immediately to safe moisture levels (below 14%);
• maintaining strict environmental controls in storage facilities to prevent moisture buildup;
• implementing integrated pest management to reduce physical damage to seeds by insects;
• using approved seed treatments and fungicides to reduce initial inoculum;
• ensuring proper sanitation of equipment and storage areas to minimize cross-contamination.