Fruit Flies, Gnats, and other Flying Insects in a Worm Bin

Eliminating Flying Insects From Your Worm Bin

The main culprits here are fruit flies/dung midges (often confused for one another) and sometimes house flies. The way to handle both of these critters is the same and fortunately is pretty easy. Here are some methods:

1. Don't Leave Nutritious Food Exposed

If your food scraps are buried under the surface of the bedding it will help in two ways. First, the flying insects will have a harder time finding it, and secondly, the worms will have an easier time finding it which means they'll eat it quicker before any other competitor could find it.

2. Freeze or Microwave Your Scraps Beforehand

Fruit flies are the enemy, and you get to decide if they meet their fate via frost or the flame.

Freezing food waste will kill most, if not all, of any macroscopic insect life before it gets the chance to be introduced to the bin. It will also help food break down in the worm bin once it thaws as the thaw/freeze cycle will cause the cells to burst within the fruit/vegetable waste. Freezing is also a good way to store your food waste if you have more than your worms can handle at a given time. 

All around freezing food waste first is a pretty good practice.

However, if you'd prefer to see the dreaded fruit flies burn, you can briefly boil your fruit/vegetable waste beforehand.

And if you really hate these guys, you can harness nuclear power and microwave food scraps shortly.

3. Keep the Moisture Just Right

Fruit flies, gnats, and especially maggots (which become house flies) love anaerobic conditions. Ensure your bin's moisture level is like a wrung-out sponge. It should be dry enough that it could soak up more moisture if provided, but wet enough that the worms don't have to worry about drying up.

4. Avoid Overfeeding

This is a great rule in general. If there is too much food for the worms are they are leaving behind "leftovers," other organisms, such as fruit flies and gnats, will take advantage of it. If you are starting to see too many fruit flies cut back on your feedings so there's no excess food other than what the worms can eat in 2-3 days time.

5. Set Up a Fruit Fly Trap

If fruit flies have already established you can set up a trap to catch them. Any open container with apple cider vinegar and a drop of dish soap will attract and drown them. Place it near your bin and you should see it start to collect little bug corpses.

In Summary

A healthy worm bin generally will not harbor flying insects, so if you encounter them do a double check on the moisture and food levels in the bin. From there you can go on the offensive by setting up a trap to catch them, and set in some longer term prevention strategies such as freezing your food scraps.