Fighting Fruit Flies

Female fruit flies can lay as many as 500 eggs in fermenting fruit and garbage.

Fruit flies win the “Most Annoying Pest” contest hands down. They live in the kitchen, crawling around and breeding on food, and then fly into hard-to-swat, in-your-face swarms when disturbed. If that behavior isn’t a category winner, I don’t want to see the competition!

Fruit fly (Drosophila melanogaster) invasions usually coincide with the ripening of summer fruit. Nothing draws a crowd of fruit flies like a bowl of peaches or tomatoes! So where exactly did they come from? Although it’s tempting to think of these pests as alien invaders that hitchhiked from a distant land, it turns out they’re natives. They usually live outdoors, though, and only come inside when they detect a potential breeding ground.

Fruit fly adults only live for a few days, so their need to breed is intense. Females lay up to 500 eggs on any fermenting food source, and that includes everything from ripe bananas to garbage disposal slime. Yuck! The presence of fruit flies is often the first tip that you’ve got a forgotten potato in the cupboard or that your toddler spilled apple juice under the table.

A fruit-fly trap with a ceramic enclosure

Despite the annoyance factor, fruit flies perform an important public service. Their larvae consume decaying matter that might otherwise turn into a source of fungal or bacterial infection or attract even more obnoxious pests, such as mice or rats. Females lay their eggs just under the surface of decaying fruit and other foods. After hatching, the grubs spend three or four days eating before they mature into breeding adults, and the cycle begins again. Their whole life cycle occurs in about eight days.

Getting fruit flies out of the kitchen takes a bit of persistence, but it isn’t difficult and doesn’t require any pesticides.

• Eliminate or contain their food sources by refrigerating or covering ripening fruit, especially bananas, peaches and tomatoes.
• Cover your kitchen compost.
• Search the cupboard for potatoes and onions that have exceeded their expiration date.
• Mop up spills under the refrigerator and rinse out discarded bottles and cans, especially beer and juice containers.
• Clean out the garbage disposal and follow your nose or fly swarms to other infestation sites.
• Set up a fruit fly trap. These consist of an attractant, such as cider vinegar, inside a bottle or container from which the flies can’t escape. A cone of paper set above a bit of vinegar in a glass or bottle works for some. I prefer the more aesthetically pleasing fruit fly trap . To prevent future infestations, I keep a trap on my kitchen counter all year around.