We were discussing over Yom Tov the inyan of using an Esrog Shvi'is for the purposes of noi succah. Is it permissible to get hana'ah out of it such as by hanging it in your succah. What are the sources for this Halachah?
The author of Sefer Mishpetei Aretz, Shevi'is 24:1, permits hanging it as a Sukah decoration (with the condition that it will not become ruined there from the sun or other elements).
The Acharonim discuss a number of points in this regard:
1) It is only permitted to derive benefit from fruits of Shevi'is in a manner in which the benefit is derived at the same time that the fruit is consumed (such as through eating), but not in a manner in which the benefit is derived after the fruit becomes consumed (such as by making it into coals and then using it as fuel for cooking).
Here, the benefit being derived from the fruit before the fruit becomes consumed. Is such a Hana'ah permitted? The Acharonim cite the Ba'al ha'Me'or in Sukah (40a) and Rebbi Akiva Eiger in Bava Kama (101b?), who permit deriving benefit from fruits of Shevi'is in this manner. Even though Tosfos there (DH she'Hana'asam) implies that it is prohibited, it could be that the case to which Tosfos is referring is when it is not possible to eat the fruit after deriving benefit from it, and that is why such benefit is prohibited -- for deriving such benefit prevents the fruit from being consumed in a proper, Shevi'is-manner.
2) A fruit or other food that is used as a Sukah decoration is prohibited to be eaten for all seven days of the festival, because it is "Huktzah l'Mitzvaso," designated exclusively for the Mitzvah of decorating the Sukah. Accordingly, it might be prohibited to make fruits of Shevi'is into Sukah decorations because it is prohibited to decrease the amount of time for eating fruits of Shevi'is, just like it is prohibited to decrease the amount of people who may eat them (such as by mixing them with Terumah, which only Kohanim may eat).
However, the Mishpetei Aretz there cites in the name of Rav Elyashev, shlit'a, that it is permitted, because it is not considered to be decreasing the amount of time that the fruit can be eaten except where it will no longer be permitted at all to eat the fruit after it becomes Asur. Fruit used for Sukah decorations, in contrast, will become Mutar again after the seven days of Sukos have passed.