http://insects.about.com/od/insectssociety/qt/Make-A-Vinegar-Trap-For-Fruit-Flies.htm

It works with red wine vinegar, but apple cider vinegar is the best.

Some relatives brought over a huge basket of fruit...and fruit flies. Don't leave any fruit out, put it all in the fridge. Take a small bowl, put in some vinegar, cover with saran wrap and punch some holes in the top of the saran wrap. That way the flies get in but can't get out. Google fruit flies and there are other suggestions there, too. But the vinegar worked for me, after I put all the fruit away.

I belong to a CSA and have noticed in the last several weeks that within hours of bringing home the produce there is a swarm of fruit flies in the house (no exaggeration). They are literally everywhere. I even opened the freezer and some came out. I don't know how they survived. I've tried washing the produce immediately in water and bagging them. As soon as I take the produce out (even days later), the they are back. This doesn't happen with grocery store produce obviously (or it wouldn't survive transit). It's pretty unappetizing. It's so bad I'm considering not getting the rest of the shares (which last until October).

Any suggestions?