People have been writing about ways to get rid of fruit flies since fruit, flies, pens and paper were created. Some say you should refrigerate all fruit. Others say you should buy commercial traps. But we have the end-all, be-all, now-and-forever answer thanks to Todd Schlenke, assistant professor of biology at Emory University, who spends all day studying these pesky pests.
Schlenke works with the genus Drosophila—as opposed to the larger Mediterranean fruit flies that live in orchards—and studies their immune systems and resistance to insecticides. Despite a really fantastic photo on his website that shows him and "Team Schlenke" wearing fruit fly t-shirts to a Drosophilia conference in Chicago, Schlenke swears he's not a fly guy. "I'm not interested in flies per se; I'm just interested in them because they're useful to answer scientific questions."
Fruit flies may be tiny, but they have a powerful sense of smell and pick up on "odor plumes" that emanate from your home. "Fruit flies spend their whole lives searching for the smell of rotting fruit, then get in through cracks in the door or however the smell is getting out of your house," Schlenke says. "Fruit flies don't actually eat fruit, despite the name. They eat the fungus or rot that grows on the fruit. So the best thing is to not let your fruit rot."
According to Schlenke, a brown banana isn't a problem—it's fruit that's molding or visibly decaying in your kitchen that attracts the flies. If fruit is left to rot for long periods of time, fruit flies can lay and hatch eggs on it. "It's rare that flies are reproducing in your house unless you have rotting fruit around a lot," he says. "In the best conditions it takes 10 days to go through their whole cycle from larvae to pupae to metamorphosis."
But if fruit flies have made themselves at home in your kitchen, Schlenke says the best way to get rid of them is to give them a nice glass of wine and say goodbye. "Fruit flies like the smell of rotting fruit because they eat the microorganisms, like fungi, that make up the rot. Fungi convert fruit sugars into energy using the process of fermentation, of which alcohol is a byproduct," he says. "So if you have a glass of wine—which is really fermented fruit—or vinegar—which is really, really fermented fruit—that's where they want to be."
And that's where you want a funnel to be. "Fruit flies will go through the hole for that smell and get trapped in the liquid," Schlenke says. "Around the lab, we make traps like that with vinegar all the time. If you want to make it even better, you can put baker's yeast in the vinegar as well."