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Global Worming News, Issue #105
September 08, 2014

How to deal with fruit flies in your worm farm


I trust you are well and your worm farm is flourishing.

We often get questions by concerned worm composting friends about the occurrence of fruit flies in worm farms. There are actually a few ways to dramatically reduce the fruit fly population in your worm farm.

Fruit flies are attracted to fruit and as such can often be found in worm farms, compost heaps and worm bins.

Although they are essentially not harmful to the worms they can become a nuisance if they are allowed to multiply. They can be identified by plump bodies that are usually pale brown or orange and a slow flight. They are between 1 to 2 mm / 64th to 32nd of an inch big.

Mature flies lay their eggs on the peels of fruit, especially bananas. Those eggs are to small to be recognized by the human eye. When the conditions are right (warm and humid) the flies hatch and can quickly multiply if the environment is to their liking.

Reducing fruit flies

Follow the steps below to reduce or even eliminate the fruit fly population in your worm bin.


1.) Place all your fruit peels and rotting fruit that you want to add to the worm bin over night in a freezer before you put them into your worm bin. This will kill all eggs that are on the fruit and peels.

2.) Place the kitchen scraps for about 1 minute into a microwave oven to kill eggs that might be on the fruit and peels.

3.) When you want to add fruit peels and fruit to your worm bin dig a trench through the center of the worm bin and dump your waste into the trench. Then cover the worm food with already processed worm castings.

The casting will act as a natural barrier against the flies.

Building a fruit fly trap

Another way to keep those tiny invaders out of your worm farm is to catch them with a trap.

To build a low cost fruit fly trap.

1. Take a large empty Soda plastic bottle, cut of the neck just above the place where the round turns into the straight line.

2, With a sharp nail or scissors punch 5 or 6 holes 2 to 3 mm / 32nd to 48th of an inch in diameter into the side walls of the bottle about 10cm / 4 inches above the bottom of the bottle.

3. Throw a few banana skins into the empty bottle.

· Place the cut off top peace upside down into the opening at the top of the bottle base. It should look like a funnel now.

· Make sure that it fits tight and no gaps are left open.

4. · Attach the funnel top to the bottle base with some clear sticky tape.

· Place the trap a few meters away from the worm farm on an elevated place...

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You can prepare a few of them slightly modified and place them in different locations to find out which works best.

Now open the lid of the worm farm and chase out as many of the fruit flies as you can than close the worm bin again.

The flies which have an excellent sense of smell will get attracted by the banana skins to the traps and crawl into the small holes on the side or the funnel opening at the top.

Most of them will not find the way out again. You should catch most of the fruit flies that have been inside your worm bin within 48 hours.

Once your traps are full either release them somewhere else or wait till they are dead and feed them to your worms.

If there are more flies left set up the traps again till you have caught the remaining ones.

If you have further questions or suggestions please feel free to contact us.

We love to hear from you. Till next time.

All the best and happy worming

Stephan Kloppert

Author of "How to start a profitable worm business on a shoestring budget"

Use worms against climate change

Earthworms for a better Garden

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