Hi,
Well, depends on your weather.
If you've got brutal weather protect the tree before the first -10°C / 14°F - but it'll be a pain, as you need to remove yourself all remaining leaves and fruits.
If your weather is not brutal, wait for leaves to fall and for the stems to dry a bit in an effort to prevent mold (remove all remaining fruits and leaves as those might turn into a mold propagation area ).
Here I have two big dips (normally) one in December and one in February. So my target is installing the protections before 1st of December.
Before, I used to install them before the 1st of November ... I'm still monitoring the weather ... Just in case ...