Among the things that the Mishnah prohibits selling to a pagan idol worshiper are:
itztrubolin – pine cones
b’not shu’ah – white figs
ptotarot – stems (of the abovementioned itztrubolin and b’not shu’ah, which were hung by their stems in front of the idol)
levonah – frankincense
tarnegol lavan -a white rooster
All of these are forbidden to be sold since a Jew is not allowed to assist a non-Jew in performing pagan idol worship. As one of the seven Noachide laws, such worship is prohibited to the non-Jew, and therefore forbidden to the Jew because of lifnei iver lo titen mikhshol – the prohibition against putting a stumbling block before the blind (see Vayikra 19:14).
Unlike the items that are mentioned as being forbidden to sell to pagans specifically around festival time, these cannot be sold to them throughout the year. These are items that are used specifically for pagan sacrifice, or else they are things that are difficult to find that are used for such sacrifice. For these reasons we fear lest they will be sacrificed even though it is not the holiday, or else that they will be held for use at the next holiday. The Ra’avad notes that we do not have such concerns when we sell an animal to the pagan, since animals are available at all times, as opposed to these things that are more difficult to find.
The term itztrubol comes from the Greek strobilus that refers to any round object, but specifically to the fruit of one of the different types of pine tree. Pine cones, which were used for medicinal purposes as well, were used to sacrifice to Asclepius, the Greek god of healing.