Whose Pears

Pinny from Petach Tikva asks:

We follow the opinion of the
Chazon Ish, that produce grown on land owned by non-Jews within the borders of
Eretz Yisroel does have kedushas shvi’is. I just acquired a large
quantity of pears grown by non-Jews. Am I required to do bi’ur on these
fruits? If so, when?

Firstly, since these fruits have kedushas shvi’is, it
is generally accepted that there is a requirement to do bi’ur (though
some opinions disagree). However, if they were still in the possession of the
non-Jew at the date for bi’ur, they do not become forbidden to eat. The
simple reason is that a non-Jew is not bound by sh’mittah laws and was
under no obligation to declare his fruit ownerless. The obligation to perform bi’ur
only arrives once ownership of the produce passes to a Jew. He must perform bi’ur
on the day he receives the fruit. (Those who hold that there is no requirement
to perform bi’ur argue that since the grower of the fruit was exempt from
bi’ur, it remains exempt [Rash HaZokein.]) There is no
exact time for performing bi’ur on pears (as is the case with many
fruits). It could be any time between the first of Marcheshvan to the first of
Kislev. Accordingly, if one bought pears grown by a non-Jew after the first of
Kislev, one should declare them ownerless in front of three people on the day of
acquisition. One may then reacquire them. Had one acquired them during the
period of doubt, one should have taken them home without reacquiring them till
the period of doubt had passed (if not eaten beforehand!).