Collecting candy on Halloween still appeals to Del.

find gerund phrase and tell if it is the subject, predicate nominative direct object or object of preposition

http://www.chompchomp.com/terms/gerund.htm

What do you think?

Collecting candy on Halloween and it is the subject

You're right.

The gerund phrase in the sentence "Collecting candy on Halloween still appeals to Del" is "collecting candy on Halloween." In this sentence, the gerund phrase functions as the subject of the sentence. It serves as the main topic or theme of the sentence and tells what is being discussed or talked about. It is not serving as a predicate nominative, direct object, or object of a preposition in this case.