How long can a pie be left unrefrigerated?

The answer is this: It depends upon what type of pie you're thinking of.  Because cherry pie is acidic and contains a lot of sugar (which is a preservative), it’s probably safe to leave it at room temperature, covered, for as long as a day or two if it doesn’t contain any eggs or dairy products. But keep in mind that refrigerating it sooner than that will extend its shelf life. Also, in a warm climate, refrigerate it sooner.

It’s also likely that a store-bought cherry pie can remain on the counter or table for 24-48 hours maximum. Read the ingredients to be sure it doesn’t contain eggs or dairy products. Most fruit pies do not contain these ingredients either in the filling or the crust. (Traditional pie crusts are made with flour, fat, and salt.) However, if eggs and/or dairy are used, refrigerate the pie as soon as possible. Leftover pie can last there about a week.

Unlike traditional fruit pies, pumpkin, pecan, custard, and cream pies require prompt refrigeration. In these types of pies, bacteria will multiply rapidly at room temperature.

Source(s):

AllExperts “Food Safety Issues—pie safety”
http://www.ochef.com/457.htm

extension.org “Pies, Other Foods Could be Dangerous at Room Temperature”http://www.extension.org/pages/Pies,_Orher_Foods_Couild_be_Dangerous_at_Room_Temperature

Link(s):

AllExperts “Food Safety Issues—pie safety” 

http://www.ochef.com/457.htm