Can you eat supermarket fruit without washing it since it was already washed before it came to the supermarket at least once, usually many times?
The reason for washing fruit, aside from general cleanliness, (as it might have fallen on the floor, and/or was handled by numerous hands between the tree and your home) is because of wax that is sprayed on to the fruits, and some vegetables. There can be kashrus concerns regarding the wax, as some waxes come from non-kosher animal sources, and “shellac” comes from a tiny insect (although R’ Moshe Feinstein ruled that it is permitted, others argue). At one point, most waxes used in the United States were not problematic, according to R’ Y. Belski zt”l). In general, though the wax will not come off by merely washing it, scrubbing the peel with a brush, or peeling it will remove any kashrus concerns.
R’ Yisroel Belski zt”l is quoted as to have said, that although there is convincing reasons to be lenient in regard to the wax on fruits, nevertheless, it would be very fitting for a hechsher to be given on such waxes.