Sweet and overripe foods are a draw for fruit flies

Where do fruit flies come from? Thin air? Just when I think the cold has killed them off, I open my trash or open my fridge and find another one, or two, or three. During the summer, I can't leave a piece of fruit out for five minutes before I'm bombarded by these pests.

— Daniel F., Medford

Daniel, if we knew exactly where they were hiding, they would be extinct, and we would be rich.

But you can rule out spontaneous generation, that's "been disproven for a few hundred years," said Rick Hilton, an entomologist at the Southern Oregon Research & Extension Center.

Some spilled juice, a dirty washcloth, the garbage disposal, a glass of wine or ripe fruit is all it takes to rouse fruit flies from their anonymous abode.

"They are hanging around, who knows where, and the warmth and fruit smells make them active," Hilton says.

Female fruit flies can lay as many as 500 eggs in their lifetime, which generally lasts only one to two weeks.

According to an article by entomologist Michael Potter, the females typically "lay these eggs near the surface of fermenting foods or other moist, organic materials."

It's quite likely that at least some of the fruit you buy at the grocery store has larvae on it that hatches later in your fruit bowl.

"Bananas are their favorite," Hilton said.

Daniel, start by cleaning your kitchen, throwing out overripe fruit and taking out the trash. If they continue to appear, there are a few nontoxic, inexpensive methods to eradicate them.

One of these is to place a banana peel inside a clear plastic container that has a few small holes punched in it. The flies will be lured inside but won't be able to find their way back out. You can release them outside or kill them. Let your conscience be your guide.

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