Penicillium ulaiense

Systematic position and pathogen type. Penicillium ulaiense is a pathogenic fungus within the kingdom Fungi and the genus Penicillium. It is a highly specialized plant pathogen recognized as one of the most aggressive post-harvest agents affecting citrus fruit, causing significant economic losses in the fruit packing and distribution industry.

Diseases and host crops. This fungus is the primary cause of olive green mold, which affects various citrus species including oranges, lemons, and mandarins. The disease is characterized by the rapid development of olive-green sporulating mycelium on the fruit surface. Unlike other common penicillium species, P. ulaiense is notorious for its ability to spread rapidly by contact between infected and healthy fruit in storage.

Biology and life cycle. The life cycle of Penicillium ulaiense is heavily dependent on fruit wounding. The infection typically initiates through injuries, such as cuts or bruises, on the citrus rind. Once inside, the fungus colonizes the internal tissues, secreting enzymes that degrade the fruit cell wall, eventually leading to the production of abundant conidia that facilitate further dispersal through the air and handling equipment.

Conditions for development and harmfulness. The pathogen thrives in environments with high humidity and moderate temperatures, although it exhibits significant tolerance to low temperatures typical of cold storage facilities. Its harmfulness is extreme, as it can cause complete decay of citrus batches within a very short period if not properly managed, resulting in high levels of waste and financial damage for producers.

Protection and control measures. Successful management relies on a strict post-harvest management program to mitigate the risk of infection. The core strategies include:

• Minimizing physical trauma during harvest and packing processes.
• Maintaining optimal airflow and humidity levels in storage areas to inhibit fungal growth.
• Strict sanitation protocols for warehouses and transport machinery.
• Prompt removal and disposal of any fruit showing signs of infection to prevent contact spread.
• Application of safe and regulated post-harvest fungicides or biological control agents.