Flies in Worm Compost

Guides to Making Worm Compost

“I enjoy using my vertical worm compost bin – and have many thousands of worms now working away at our daily garbage refuse – but we also seem to be harboring many more thousands of tiny fly larvae – I’ve tried covering with several layers of wet newspaper, used coffee filters, and egg shells, but the top few bins seem to be real magnets. Help!” ~ Diane from Detroit

I understand your pain with flies in vermicomposting and I am sure it is a big problem with many people out there. Unfortunately having flies is part of a normal composting process, but there are ways to minimize the problem.

First of all, many people mistake the very small white worms as fly larvae, where in fact they are more likely to be pot worms. These are also some times mistaken as baby earthworms since they are quite similar in size, but the difference is that baby earthworms are pinkish in colour while pot worms are pure white.

Pot Worms in the Wormery

Pot worms are perfectly fine in a wormery, although they can multiply very quickly. It is also very unsightly when you look into a wormery with thousand of tiny wiggling white worms all over the place (it’s not a surprise they are mistaken for larvae). Pot worms feed on the same material as the composting worms, and will break it down in a similar way, so having pot worms can aid with the vermicomposting of your waste.

Although it seems that pot worms can benefit your vermicomposting system, having a large population can be a bad thing because they thrive in more acidic conditions. This means that a large population of pot worms is an early indication of an acidic bin, and a pre-warning to you to start doing something before it gets worse.

If you do want to get rid of pot worms, you can use bread soaked with milk to attract them. The pot worms will be attracted to the piece of bread which you can then remove and dispose of or burn.

Fly Eggs & Larvae (Maggots) in the Worm Compost

What about if you have identified the little crawlies are actually fly larvae (maggots)? Then that can be good new and bad news.

The good news is that they are very efficient in breaking down wastes. Unlike earthworms, which suck in partially broken down food and microbes, the larvae attack and breakdown the food waste directly and very quickly too. Their presence in a worm bin can lead to happier healthier worms, since the larvae break down waste into a material more easily consumable by the worms.

There are many different types of fly larvae, and there are a group of people who uses only black soldier fly (BSF) larvae for breaking down their waste in a specially made BSF composter, with break down rates being as fast as 24 hours! BSF larvae are much larger though, and is unlikely to be the ones you have in your bin.

The bad news is that it is unsightly and very annoying once they hatch. One of the last things most people want when they open their worm bin is to have a swarm of flies flying out to them, whether or not they are near their house.

How do fly larvae get there in the first place?

A lot of them are actually introduced while disposing of the waste!

The eggs are laid when the waste is exposed and hatches when they are in the bin. It is very logical why so many eggs are found in the surface of a compost pile. Flies lay eggs near a food source to ensure there is food for their young when they hatch. Flies cannot dig and so their eggs are always deposited on the surface.

There are ways to minimize the problem and you have done well so far to cover up the surface with newspapers, although I am not too sure what the coffee filters and egg shells will do to help though – as they may attract more fly larvae.

The Three main ways of fly larvae minimization are:

Burying waste / covering waste
Fly Traps
Stop feeding

You have done the right thing by covering the surface with newspaper. But with the introduction of fly larvae already underneath, newspaper will do little to help reduce the problem. Try burying your waste and then covering it with soil or newspaper. Make sure that the waste is not exposed. Worms will be able to process the food, while flies will not be attracted to lay their eggs on the surface anymore.

Fly traps are a good way to remove immediate fly numbers, but will take a while before you will see larvae numbers falling. The idea is to reduce the number of flies to reduce the number of eggs being laid. Building a fly trap can be really simple and have been mentioned in my previous posts or searched online.

Fruit flies and vinegar flies are attracted by vinegar/ wine and other fruity fermented smells. Taking a jar with a small opening and filling it with a little vinegar will attract the flies into the jar. Miraculously once they are in the jar they rarely climb back out and will mostly drown in the vinegar. You can build a few of theses and place them around your worm bin.

If larvae and flies are a big problem, the last thing you can do (and most practical) is to stop feeding food to the wormery system. Worms can survive without food for many weeks without a problem, but flies have a quick life cycle.

Without food, flies with not lay their eggs and may try and find another source to lay their eggs in. Within two weeks, all the eggs in the wormery system will have hatched, and without new eggs being laid, your problem will be solved where you can then started feeding your worms again!

Tip to Stop Flies Getting into the Wormery

If you are feeding worms your food scraps, one more way to prevent the introduction of fly eggs into the bin is to microwave the peelings and waste that you are about to throw into wormery. This will kill off any eggs leaving your wormery fly free!

Allotment Growing UK has been granted exclusive & sole permission to republish the above article for the benefit of it’s visitors who are interested in composting with worms. Originally published in the excellent free worm composting newsletter – Worm Farming Secrets

If you would like further information, an excellent step-by-step “how to” guide, or have your own unique worm composting questions, be sure to visit Worm Farming Secrets now. With over 17,000 readers, Worm Farming Secrets is quite simply the leading worldwide authority on composting with worms. Click Here Now.