I would get them fumigated if I were you - why take the chance!Remember, at the border, its a case by case basis and depends on the officer...(one could be having a bad day and he'll go strictly by the book, the other might have won a lottery and would not be so bad)...Im just making assumptions in order for you to realize that if its written as a requirement, why drag the mattress all the way without fumigation only to dispose it at the border which is a hassle in itself...its called better be Safe than Sorry.

Cheers.