Beautifully written poem that deals with the subject of purity and temptation in the Victorian era.
In my opinion this poem is a slight parallel of Eve and her fall from grace when she was tempted by the snake. Purity was an important virtue during the 1800s, so the fruit (instead of representing knowledge) represents sex and being tempted by passion.
Once someone tastes the fruit, this person is doomed to a life of misery as a form of punishment for not being able to restrain their urges. In a way the moral of the story is that if you fall into temptation and lose your purity you will die. Obviously now a days the moral of the story sounds drastic, but in the 1800's a true lady had to keep herself pure and innocent till marriage so having a poem teach "sex kills" was logical.
Even though this moral seems a bit out of date it also has insight into human nature. In a way, it's basically a reflection of what happens when you allow the Id to determine your choice of action without having listened to the ego or superego. Sure, repressing every urge is unhealthy but we can't let our animal instincts reign free. People now a days seem to confuse freedom with letting our instincts take hold, but human's are rational and can only achieve real freedom by mediating and thinking about what they should do. Everything in excess can be harmful for the mind and the body. Drinking to oblivion because you can is basically choosing to experience life through a caged perspective, when you are drunk the choices you make are basically taken by the Id, and your mind has less control and freedom over what you are doing.
Of course, sex is different to drinking, but I think this poem doesn't necessarily have to be applied to sex (even if it was written for that purpose), it can apply to anything that can tempt a person and cause addiction.