Fruit Fly Traps

At some point we brought home a fruit fly starter kit that produced a zillion fruit flies in the worm compost bin; every time we opened the cover, half a zillion flies would emerge. After a bit of fiddling with the usual Internet recipes, I managed to produce something useful:

Fruit fly trap - overview
Fruit fly trap - overview

The trick involves making the liquid enticing enough to get the flies through the hole in the coffee filter top:

Frut fly trap - filter paper
Frut fly trap - filter paper

I used about a cup of water, an ice cube of apple juice for sweetness (they are, after all, fruit flies), a tablespoon of vinegar for that delicious rotten aroma (they prefer damaged, easy to eat fruit), and a few drops of dishwashing detergent so when they hit the liquid they’re sunk.

The container must be tall enough to let them rise past the entrance opening on their way toward the light; I settled on the 2 pound ricotta cheese containers we have in abundance:

Fruit fly trap - results
Fruit fly trap - results

That’s the catch after maybe a month at the end of the season, but it represents a week of activity back when we were breaking the infestation. I deployed four of those traps atop the compost bin to catch the half-zillion escaped flies and fired up the vacuum cleaner to extract the half-zillion remaining inside every time we opened the lid. After a few weeks of that, we’d managed to get ahead of their breeding cycle and the problem pretty much Went Away.

9 thoughts on “Fruit Fly Traps

  1. Those little bastards are so annoying. The best trap I found was any kind of wide mouthed, shallow glass or bowl filled with a bit of apple cider vinegar and a drop of soap. With traps they would meander around cone and the lips of the thing. Going into the trap was a random occurrence at best.

    I went so far as to make an active trap for the little buggers using a PC fan. The fan would blow straight up and out creating a vacuum around the lip of a mason jar. It worked well but, it also diffused a LOT of apple cider vinegar into the air and a bit on the noisy side.

    1. Going into the trap was a random occurrence at best.

      The first iteration of this using a shallow container didn’t work at all: the shallow filter paper cone allowed them to wander back out as they buzz around near the upper rim. Making it a few inches taller seemed to solve that problem.

      And that sour apple juice must be just the yummiest stuff ever…

      make an active trap for the little buggers using a PC fan

      You’re crazy. You know that, right? [grin]

      (I can make that diagnosis based on just one picture. I know the symptoms.

      1. What can I say, it’s a sickness :) The boss was kind enough to let me run it long enough to tell if it was effective. After that she determined the flies were less of a bother than the smell.

        Sorry, I wasn’t very clear on the shallow wide container. What I should have said was to use a shallow wide container sans cone. The flies are more likely to fly in and perish in the bait than they are to wander their way down to the small opening of a cone.

        1. a shallow wide container sans cone

          Ah! Now I get it: maximize the area under the lid and minimize the opening around the circumference.

          If When they return next year, I’ll do … Science!

  2. I’ll second the apple cider vinegar and drop of soap as bait. Extremely effective here. I also used a mason jar and made a cone of paper that I held down with the mason jar metal ring. A relatively big hole in the bottom was pretty effective (about nickel sized).

    1. A relatively big hole in the bottom was pretty effective

      My first pass at the taller containers had holes about that size and we thought the flies got out far too easily. However, your clear glass jars have the advantage of bright light near the top that probably attracts them more than the diffuse light through the white plastic I used.

      Another good idea for next year’s crop… thanks!

  3. “I settled on the 2 pound ricotta cheese containers we have in abundance”

    Inquiring minds want to know: where does all the ricotta go? How about a recipe or two…:-)

    1. A dollop of ricotta goes into my breakfast porridge to raise the protein and calcium content. The porridge is a mix of oatmeal and bulghur-soy grits. I also add milk and blueberries. Ed shuns this mix.

      My other use for ricotta is making lasagna. I make a big tray and freeze most of it.

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