Want to trap (and kill) fruit flies? Here’s why you should use bananas or red wine

Fruit Fly
Fruit Fly

No doubt. You are sitting at home right now admiring the abundant harvest you’ve just gleaned from your garden. A plethora of fruits and veggies just waiting for you.

Unfortunately, along with a crop of tomatoes, bell peppers, merlitons, aubergines and courgettes, you’re also harvesting young fruit flies. Even if you thoroughly wash the fruit, the maggots will still be there, eating away at your precious plums. Within a week or less, they will have emerged into whatever environment you’ve placed them.

If it’s in your house, you could have a problem. At least, an esthetic one. While fruit flies are especially attracted to ripened fruits and vegetables in the kitchen, they will also breed in cleaning rags, drains, empty bottles and cans, garbage disposals, trash cans and mops.

All they need is a moist film of fermenting organic material. Fortunately, in the controlled environment of your house, it shouldn’t be too bad a problem to tackle.

The first thing to do: avoid problems with fruit flies in the first place. This means eliminating any sources of attraction. Eat, discard or refrigerate ripened fruit. A single rotten potato or onion stuck in the back of the cupboard, a spot of spilled fruit juice under the fridge, a can in your recycling bin with a few forgotten droplets of beer or cola still in it. All of these can breed thousands of fruit flies very quickly. Females can lay up to 500 eggs.

If it’s too late for the first step and you already have fruit flies buzzing about, you have to begin by cleaning up all potential breeding areas. Unless this step is completed, anything else you do will be a complete waste of time. Finding the sources can be challenging and will require persistence.

Some sites that are inaccessible (such as garbage disposals and drains) can be inspected by placing a clear plastic storage bag over the opening overnight. If flies are breeding in that spot, the adults will emerge and be caught in the bag. To reduce the numbers of fruit flies, use a drain cleaner to eliminate some of the build-up in which they’re breeding.

After you've managed to find and eliminate the source of breeding, you can use one of the commercial bug-bombs to get rid of any adult flies that are left. If you have some objection to using insecticides, you can try trapping the remaining flies. There are commercial fruit fly traps available. But there are a couple of less expensive methods that have always worked reasonably well.

One is to use a small jar, plastic wrap and a bit of bait. Here's what you need to do:

▪ 1. Find a small container like a baby food jar and wash it thoroughly. Don't use a pickle jar or one with a funky smell. You want a clean, odorless container.

▪ 2. Place a small piece of banana and put it inside the jar. Banana works well but you can experiment. Red wine is also very attractive (but, for some reason, not white wines).

▪ 3. Top the trap with a piece of plastic wrap, making certain that it's a tight fit. Take an ice pick or similar object and poke four or five small holes in the wrap. The holes should be just large enough for the flies to enter the trap (3 millimeters or 1/8th inch). Once the fly enters the trap through the hole, they won't be able to get out.

▪ 4. Place the trap in the area where you've seen the most flies. Depending on the infestation, you'll probably start to see flies in your trap in just a few hours. Within 24 hours, you should know just how bad your problem is.

Another method is to use a small plastic bottle. Cut off the top at its shoulder. Place a few ounces of cider vinegar into the bottom of the bottle. Invert the section you cut off back into the bottom of the bottle. This makes a funnel that allows the flies to enter. But most won’t be able to get back out. To kill the flies, cover the top and shake. This will drown the flies.

These are safe, easy and cheap methods that works consistently well. If you don't want your trap on public display, you can hide it behind the garbage can, in a cupboard or under the sink. You'll want to empty the trap every three or four days before the eggs have time to hatch out.

Don't forget about them. The grown ups may not be able to easily escape from the traps but the young maggots can. The last thing you want is a mass of maggots stampeding about your kitchen.

In heavy infestations, you may want to keep the traps going for at least two weeks. Before you know it, your fly problem will disappear. At least until you bring your fall harvest of lemons and oranges into the house.

Tim Lockley, a specialist in entomology, is retired from a 30-year career as a research scientist for the U.S. Department of Agriculture. For answers to individual questions, please send a stamped, self-addressed envelope to Tim Lockley, c/o Sun Herald, P.O. Box 4567, Biloxi MS 39535.