Getting rid of annoying compost fly infestations

Ever had a swarm of bugs fly out when you open the lid of your compost bin?

They are compost flies. Tiny and harmless insects, their presence is a sign of incorrect composting.

Compost flies breed quickly in acidic conditions which arises from an imbalance in compost nutrition.

The good news is that when you compost optimally, wastes won't attract flies or other pests because they break down before they can be sniffed out.

Here are some strategies for managing a compost fly infestation.

Modify your compost

You can cause a compost fly infestation to die off on its own by spreading carbon-rich wastes ^[1] over the existing materials. Add a layer 5-7 cm thick to make conditions unsuitable for compost flies.

Keep composting with regular input of sorted wastes, as discussed in Preventative Action.

You may have to add another thick layer of carbon-rich wastes 3-4 weeks later for a severe infestation.

Compost fly trap

You can snare compost flies with a homemade trap like the one in this post's thumbnail.

Select a clear plastic container with a screw lid, e.g. peanut butter jar. Add your lure to depth of 1 cm - either apple cider vinegar or white vinegar with a piece of fruit. Make 2-3 small holes in the lid.

Place the trap near the top of your compost equipment to catch compost flies.

Preventative action

You don’t have to worry about compost flies if you put in waste composites with balanced nutrition. Use this guideline ^[2] :

Sort your compostable wastes as either carbon-rich or nitrogen-rich types and use balanced amounts of the two wastes. Place the nitrogen-rich wastes underneath carbon-rich types.

The exact ratio of carbon-rich to nitrogen-rich wastes depends on what compost equipment you use. For ordinary composters you will typically need to use a greater proportion of carbon-rich wastes.

Bioverter can handle common nitrogen-rich wastes like kitchen scraps as your main waste input, provided you spread carbon-rich wastes to cover the scraps.

For optimal composting, consistently add sorted wastes in two layers, and with the right relative amounts.