Wishfull thinkiong is a great thing...but we hit -15 last year before we had significant snow cover and they came back 3 weeks earlier than the year before...

It'd be nice and I wish you the best of luck. We could use some help around here with the pine bark beetles, but I guess it takes long periods of very very cold temps to stop them, dern it all.

I do think that bad winters slow squirrel populations some, and every little bit helps.

You can use very fine mesh netting to keep them out. I heard they have been leaving yellow cherries alone, so maybe they will leave yellow raspberries alone?

From additional reading, it seems that SWD can survive winter weather by taking cover in leaf litter at the forest edge. I am not sure it will be cold enough, for long enough, to kill them all. More research is needed.

I have seen reference to leaf litter as well. Around here there was suspicion that small populations were wintering in "moderated" environments, like barns with livestock and rootcellars.
Then you have a small local population that grows rapidly vs new populations brought north on the wind each season (like late blight) to see which reaches infestation levels first...
under either scenario early ripening berries have the best chance

Like you say more research is needed, but fortunately there are a lot of smart folks taking this very seriously..and doing the research...but it takes time to develop baseline data on a new species and how it behaves in different locations.

I am still crossing my fingers for some effective biological control or trap out system. But so far trap out has been a failure(really only useful to monitor) and biological controls are always a bit dodgy...easy to make things worse while trying to make them better.

There are a few researchers in Washington and a number in Oregon that are researching the SWD. One website that has a link to an article about over-wintering SWD.

http://mtvernon.wsu.edu/ENTOMOLOGY/pests/SWD.html

Apparently the female tends to gradually morph from an egg-laying insect into one capable of surviving the winter. I suppose that if the temperature is cold enough and surprising enough early in the season then a number of the insects could be killed. Anecdotal evidence suggests to me that is what happened in Seattle a while back.
The problem is that all it takes is a small percentage to survive and within a few generations, they are back in business again.
So what to do next season? Some researchers do indeed think netting has promise.....but it would be really nice if they could discover a natural predator or parasite for this pesky fruit fly....some leads are in that direction of a natural predator ...but there is still no silver bullet as of yet.
I would be curious to hear from anyone who has a large population of humming birds in their back yard.

I listen to a lot of gardening podcasts from CA and it seems once temps reach 85 degrees the fruit flies cannot reproduce, so late varieties work there. SWD seems more suited to the temperate environment. Hopefully if the extremes hurt them, this winter will set them back. We are having some very cold temps.