Ceratocystis fruit rot

Causative agent and disease type. Ceratocystis fruit rot is caused by the fungus Ceratocystis paradoxa (anamorph Thielaviopsis paradoxa). This is a soil-borne pathogen known for causing severe rot in tropical crops. The fungus acts by colonizing plant tissues and secreting various cellulolytic enzymes, which lead to the rapid softening and complete degradation of the host's cellular structure.

Host range. The pathogen is particularly notorious for its impact on bananas, where it is known as black end or crown rot. It also affects a wide range of other crops, including pineapples, sugarcane, coconut palms, and cacao. In many agricultural settings, it is a significant post-harvest problem that compromises the shelf life and marketability of the produce.

Symptoms and signs. The characteristic symptoms include water-soaked lesions that turn into soft, dark-brown to black rot. As the fungus matures, it produces a profuse amount of olive-black powdery conidia on the surface of the infected tissue. In banana bunches, this often results in the darkening and necrosis of the fruit ends, making them unmarketable.

Conditions for development and spread. The fungus thrives in warm and humid climates, with optimal growth occurring between 25°C and 30°C. Spores are easily disseminated by wind, water splashes, and contaminated tools. The pathogen primarily enters host tissues through wounds caused by harvesting, pruning, or insect damage, making intact fruit skin the primary barrier against infection.

Damage and control measures. This disease can cause total loss of fruit batches if storage conditions are inadequate. Management strategies focus on:

• Strict sanitation protocols in packing houses and fields.
• Disinfection of knives and pruning equipment using appropriate chemical solutions.
• Application of post-harvest fungicidal dips for fruits and systemic fungicides for planting material.
• Ensuring low-temperature and well-ventilated storage to inhibit fungal mycelium expansion.