While cold temperatures won't instantly kill household fruit flies, your average refrigerator is plenty cold enough to keep them from breeding.
Fly Science
While warm-blooded creatures, such as humans, have built-in temperature control mechanisms to help us cope with climate, cold-blooded Drosophila species lack this feature. Ideal temps for a healthy life cycle and reproduction range between 68 and 76 degrees Fahrenheit; below 68 degrees, the creatures struggle to propagate.
Target Temps
Below 60 degrees Fahrenheit, common fruit flies experience a sharp decrease in lifespan; temperatures below 53 degrees Fahrenheit inhibit their development entirely. However, it may not kill eggs and larvae already on the fruit; they may continue their arrested development when they warm up again. Because female fruit flies typically seek breeding grounds within a moderate temperature range, they are less likely to lay eggs -- the key cause of fruit fly infestation -- on produce stored at refrigerator temperatures.
Frigid Fruit
Your refrigerator, which ideally runs at about 40 degrees Fahrenheit, is a key component in the fight against fruit flies in your home. As these insects love to feed and breed on warm, ripe and rotted produce, keep fruits and veggies in the fridge to keep your home fruit-fly-free. Likewise, keep fermenting foods tightly sealed and maintain a dry, clean kitchen free of food refuse and sticky spills.