Blue and Green Mold

Blue mold can sometimes be found on fruit in the field, but it generally appears during storage. Occasionally blue mold can develop along the black heart symptoms. Initial symptoms include water-soaked areas on the outer fruit surface. Later, a green to blue-green powdery mold may develop on the surface of the lesions. Infected areas are tan or gray when cut. In advanced stages, infected arils may disintegrate into a watery rot.

Several species of Penicillium can cause blue mold. These fungi are common saprophytes on plant debris and senescent plant tissue. Invasion of pomegranate fruit can occur through wounds or bruises, but colonization usually occurs on the surface of senescent fruit. At advanced stages, the mycelium grows inside the fruit through the connective tissue and arils. Optimum conditions for Penicillium spp. development include moderate temperatures of 70° to 77°F (21°–25°C) and high relative humidity.

Good orchard management practices, such as dust control and sanitation (removal of old fruit and dead branches), can reduce the postharvest incidence of the disease. Prevent insect damage and avoid wounds to fruit. Harvest and handle fruit with a minimum of bruising or wounding.

Storing pomegranates properly can help avoid further decay:

• The optimal postharvest storage temperature for pomegranates is 41°F (5°C) for up to two months and 45°F (7°C) for longer than two months.
• Store at 90 to 95% relative humidity.
• If storing for longer than three months, a controlled atmosphere of 5% oxygen plus 15% carbon dioxide is suggested.