How to keep the fruit fly population down

From WormWiki

To prevent the next generation, keep a thick layer of bedding on top of any food. Fruit flies won't burrow ibs down to lay eggs. Easiest method if you've got an outdoor bin and don't mind a few fruit flies.

To prevent the first generation, do the above and freeze your food before giving it to the worms to kill any eggs.

To control an existing population, place a funnel in a jar with vinegar or juice or beer... in the bottom about 1/4 inch deep. An easy funnel is a zip lock bag with cut in half diagonally with the lock cut off and a small hole in a corner cut off to make a small opening. Open the bag to make the funnel, put the funnel in a jar (old yogurt container etc.) and fold the excess over the edge and secure with a rubber band. The idea is the flies can get in, but not out.