How to Eliminate Fruit Flies from Vermicompost

A fly sitting on a decomposing rind in a vermicompost pile.

Vermicompost is one of the most effective organic fertilizers. A single teaspoon of vermicompost is sufficient to feed a potted plant for nearly 2 months. It is produced from controlled decomposition of organic matter. The preparation of vermicompost from a compost pile is called vermicomposting. Here, worms begin to digest the decaying organic matter and excrete a unique, nutrient-rich material called "worm castings." Vermicompost tea or compost tea prepared form vermicompost is regarded as the single, most comprehensive source of plant nutrients. It's also called worm tea.

Unlike regular compost piles, the vermicomposter or the bin containing the pile can be placed indoors. This makes vermicompost a readily-available, easy-to-produce natural fertilizer for apartment dwellers also. The container is called a worm bin. Maintaining the worm bin is not difficult, but it does attract one universal problem: fruit flies. Fruit flies are comprised of many species of small, fast-multiplying flies under the genus Drosophila. They are also called vinegar flies or pomace flies. A common fruit fly, found in most gardens, is the Drosophila melanogaster. Eliminating fruit flies requires a bit of patience along with following a few tips.

TIP: Our expert gardening advisor, Karen Thurber suggests, "To get rid of the pesky fruit flies, try drying your bin out a bit to make it less attractive. Add dry bedding to the bottom of the bin. Also, be sure you are not overfeeding the worms, too much food, especially citrus can be problematic."

Take Care of the Peels

You should not overload your worm bin with vegetable and fruit peels. These are the favorite feeding items of a fruit fly. Fruit fly eggs are commonly found on the outer surface of fruit peels.

  • Scrubbing

If your household produces an excess of vegetable peels, then scrub them with water before dumping them in the composting pile. Scrubbing ensures that the flies aren't attracted to them. Also, peels are sometimes scattered with microscopic fruit fly eggs. Therefore, scrubbing also ensures you are not introducing fruit fly larvae in the worm bin.

  • Microwaving

A quicker method is putting the collected organic matter in the microwave and letting it cook for a minute. This ensures that the excess moisture and leaking juices from the peels are dried. It also kills any fruit fly eggs that may have been laid on the peels.

  • Manipulating the Pile

To prevent fruit flies from multiplying in the worm bin, bury the peels deep inside the composting pile. This ensures that the newly-laid eggs are suffocated due to the burden of overlying organic matter.

Use Fruit Fly Traps

These are simple, cheap and effective tools for getting rid of fruit flies. Try the soda bottle trap.

  • Making a Soda Bottle Trap

Empty and dry a two-liter plastic soda bottle. Cut along the upper end of the soda bottle, i.e. along the part that is labeled, using a sharp blade. Put sweet, fruit fluids like orange juice or vinegar in the bottom of the bottle. Now, place the cut off top of the bottle inside the bottom of the bottle so it looks like a funnel pointing down. Seal the two edges together with tape.

Place the bottle inside the composting pile. Fruit flies enter the bottle due to the fruity fluids and can't find their way out. When many fruit flies have gathered, pull-out the bottle and dump liquid.

    Check Vermicomposting Pile Ingredients

    You should never add the following ingredients to your vermicomposting pile:

    • Meat products--beef, chicken, poultry, fish and pork
    • Grease/fats--butter, margarine, mayonnaise and salad dressings
    • Dairy products--cheese, milk and yogurt

    They don’t support the multiplication of worms that is needed for vermicomposting. Instead, they lead to the multiplication of unwanted microorganisms that makes the decomposing pile more favorable for fruit flies.

    TIP: Karen recommends, "If you find you have a real infestation of fruit flies, stop adding compost to the pile for a few weeks. The worms will be fine without food for a while and many of the fruit flies will starve. At the same time, set traps in the bin to get rid of the adult flies."