Why would an orange have rotten black substance in it?

Question

uh that goes with out saying

Answer 1

toss it. could be anything, but if it stinks its probably going to make you sick,

Its black mold

Answer 2

The black substance is a type of fungus like mold.   It will not hurt you probably, but I wouldn't eat it.

Answer 3

Sounds like what we call "sooty mould". Sooty mold is not a disease of the plant as such but a fungus that grows on the sugary exudate of sucking insects like aphids, mealy bugs, waxy scale etc. The website at the link has a picture and suggests ways to treat the insects that encourage the mold.

Answer 4

Probably a parasitic fungus. I haven't heard of any that infect oranges, but I'm a neophyte to the field, and there's almost undoubtably one out there.

Answer 5

This is the start of the seeding process.  The plant invests energy to encase it's seeds in a case that when shed from the tree provides a little compost heap to give it's seeds a kick start.

Or similarly it uses the fruit to entice the seeds to be ingested, and then carried elsewhere to be deposited in it's own manure away from the parent plant.