As in every year, most esrogim used in America come from Eretz Yisroel. Most of these were grown during 5758, the Sabbatical Year, and possess kedushas shviis – “Sanctity of the Seventh Year,” and therefore must be disposed of appropriately.
According to most authorities, these esrogim MUST be returned to Israel. Although we do not live or farm in Eretz Yisroel, we have a once-in-seven-years opportunity to participate in the mitzvos relating to the sabbatical year by returning Israeli-grown esrogim to Israel. At Congregation Toras Chaim, we are therefore organizing a collection of these Israeli esrogim to be returned through recognized channels for proper disposal. After Succos, please bring your esrog(im) — preferably in the boxes you received them — and place them in the designated box in shul. We will then send them to the designated collection point for return to Israel.
If you miss this opportunity, then, according to some opinions, you may let your esrog rot or shrivel hard to the point that it would no longer be edible. You may then dispose of it in a respectful manner by wrapping it up well before placing it in the trash. Do not use Israeli esrogim this year to make schnaps, candy, jam etc. as the laws relating to all the parts of the fruit get somewhat complicated given the fact that they were grown in the Sabbatical year and maintains special sanctity.
Please note that the above does not apply to Californian, Italian (Yanaver), or Moroccan esrogim (i.e. those sold by Zaide Reuven’s Esrog Farm), as well as a small number of Mexican esrogim obtained by some people.
If in doubt as what to do, please speak with your rabbi.
Since the first exile was lengthened as a punishment for the number of Sabbatical years not upheld by the Jewish people (70), may our exile be shortened in the merit of our meticulous observance of the mitzvah of Shmittah.
A good article on this subject may be found at:
http://theyeshivaworld.com/article.php?s=shmitta+esrogim
as well as:
http://www.star-k.org/kashrus/kk-medi-shmitta5761.htm