Always handle fruit carefully to prevent bruising and refrigerate fruit promptly at 32 o to 50 o F. Remove all plant residue after harvest. The disease is caused by the fungus Rhizopus spp. The initial symptom appears as water-soaked fruit spots that gradually turn light brown. Fruit rapidly soften and collapse, and their juices leak out. The sporangiophores develop black sporangia, each containing thousands of spores, which give fruit a pincushion appearance.
Rhizopus is an excellent saprophyte, able to live on decaying organic matter.
It survives on crop debris in or on the soil between growing seasons. The fungus invades fruit through wounds and uses enzymes to break down and kill tissue ahead of the actual fungal growth. Disease development is favored by warm, humid conditions. Rhizopus produces large numbers of spores that are easily spread by wind or insects. Apply fungicides during the fruit-picking period.