Although the classic bowl of vinegar and dish soap (as described above) works perfectly against fruit flies, large houseflies, blowflies, or horseflies often reach its limits. They are too heavy, often only land on the edge, or turn away.

The most effective fly trap in the world, which also tackles large fly infestations in the house, on the patio, or in the garden, is the funnel trap made from a plastic bottle. It utilizes the natural instinct of flies: They easily fly in but can’t find their way out again.

Here are the step-by-step instructions for the ultimate trap.

The principle: The funnel trap
Flies are attracted by an intense bait, crawl down through a narrow opening, and instinctively try to fly upwards or towards the light when faced with the threat of escape. However, since the exit is in the dark in the center, they remain trapped.

What you need:

An empty 1.5 or 2-liter plastic bottle (PET)
A utility knife or scissors
Some tape (e.g., duct tape or painter’s tape)
The appropriate bait (see recipes below)
Instructions in 3 steps

1. Cut the bottle
   Cleanly cut off the top third of the plastic bottle with the knife – just below where the bottle straightens out again after the neck.
2. Insert the funnel
   Turn the cut-off top piece upside down (like a funnel, after removing the cap, of course) and place it upside down into the bottom part of the bottle. The bottle neck should now point downwards into the interior but should not touch the bottom.
3. Secure
   Secure the edge where the two parts meet with some tape. This prevents flies from escaping through small gaps at the edge and keeps the construction stable.
4. Insert the funnel The Secret to Success: The Right Bait

A trap is only as good as its bait. Depending on the type of flies you’re dealing with, you’ll need to adjust the contents:

Recipe A: For Indoors (Odorless for humans)
Large flies love sugar and fruit flavors, without the need to stink up your kitchen.

Mixture: 1 ripe, mashed banana or a piece of apple + 2 tablespoons of sugar + 100 ml warm water + a splash of vinegar (repels beneficial bees and bumblebees!).

Recipe B: For Outdoors (Extremely effective, strong odor)
If you want to lure flies away from your patio or balcony, protein decomposition works wonders.

Mixture: A small piece of raw meat, sausage, or fish + some water or slightly stale sweet beer.

Note: Place this trap a few meters away from where you’re sitting, as the odor will become very strong after 1-2 days in the sun.

💡 Pro Tips for Maximum Success

Safety Distance: The liquid level in the bait should never be so high that it touches the inverted bottle neck. The flies must be able to fly inside the bottle.

A Drop of Dish Soap: Add a tiny drop of dish soap to the liquid bait. When the exhausted flies land inside, they will immediately sink.

Utilize the Light Effect: If you cover the bottom of the bottle with dark tape, leaving only the top funnel exposed, the insects will fly even faster towards the light and down into the trap, but they will be even less able to find their way out.