From: Skyhooks
Message-id:

However, my canteloupes have some sort of silvery dust (fungus?)
covering the leaves, as one can perhaps see via the pics I included at
(http://www.picturetrail.com/skyhooks - & select garden).

It's mildew.
http://www.ces.ncsu.edu/depts/hort/hil/hil-8.html