Question:
May I use my Sukkos esrog for mundane purposes after the chag? Specifically, since its aroma (citronella) is known to repel mosquitoes, may I keep my now-dried or drying esrog near my bed and scratch it to release the scent when mosquitoes are present?
Answer:
Yes you may. An esrog after Succos is considered tashmishei mitzva, which may be used for mundane things. There you may use it as an insect repellant, the same way you may eat it. The only thing we may not do with amashmishei mitzva is to use it for a degrading use, and using it's aroma is not a degrading use.
Best wishes
Sources:
O:CH 21-1, also see Mishna Berura there.
