One frustrating pomegranate problem is fruit that appears acceptable outside but contains dark internal decay.
Alternaria fruit rot / black heart
UC IPM includes Alternaria fruit rot, often called black heart, among key pomegranate diseases in California. Because symptoms can be largely internal, diagnosis can be difficult before fruit is opened.
Don't assume every dark interior is the same disease
Several fruit rots can occur. Disease history, fruit symptoms and growing conditions matter.