Rhizopus rot

Rhizopus rot is a common fungal disease caused by various species of the genus Rhizopus. These fungi, often referred to as black molds, are opportunistic pathogens that act as both parasites and saprophytes. They are notorious for causing seed decay, seedling blight, and post-harvest rot in a wide variety of agricultural products stored in improper conditions.

The disease affects a vast range of crops, causing significant economic losses globally. Peanuts are particularly susceptible to Rhizopus infections, which attack both germinating seeds in the soil and harvested pods in storage. Other crops commonly affected include soybeans, sunflowers, maize, and numerous horticultural products that are vulnerable to storage-related decay.

Key symptoms include the rapid softening of plant tissues, which eventually become covered in a dense, fuzzy, grey-to-black mass of mycelium. The appearance of dark, pinpoint-sized sporangia is a diagnostic feature of this pathogen. Once infected, tissues become water-soaked and lose their structural integrity, quickly turning into a mushy mass that spreads rapidly in stored batches.

Rhizopus development is favored by warm, humid conditions, typically with temperatures between 25°C and 30°C and high relative humidity. The fungus produces large quantities of spores that travel through the air, water, or contaminated soil particles. Mechanical damage to the plant or fruit skin, often caused by insects or harvesting equipment, acts as a primary entry point for the fungus.

Management strategies focus on minimizing humidity and preventing mechanical injury to crops. Essential practices include using high-quality fungicide-treated seeds, maintaining proper crop rotation, and ensuring rapid drying of harvested produce to reduce moisture levels. Proper sanitation and the control of insect pests that damage fruits are crucial to preventing outbreaks in both the field and storage facilities.