Flies and Maggots

11 February 2019  |  HOTBIN Composting

Flies and maggots are fortunately uncommon visitors to the HOTBIN but can prove irritating little critters once in situ. Their presence though does indicate that your HOTBIN is probably not up to hot composting temperature (40-60°C). In order to eliminate flies and maggots from a HOTBIN, it is important to understand the types of fly that are found in and around your HOTBIN, appreciate how they may get into the occasional HOTBIN and look at ways to get rid of them once and for all.

What types of flies are associated with compost bins?

House flies and fruit flies are the two main species of flies found in and around compost bins. Both thrive in a warm environment with access to plenty of fermenting and decaying material to eat and lay their eggs in.

How can the flies and maggots get into a sealed HOTBIN?

When given the opportunity, flies will lay their eggs in any moist and warm decaying matter. They especially love kitchen food caddies or waste jugs when the lid is partially or fully open. Once living amongst the food waste, female flies lay batches of between 120-150 eggs which will hatch within 72 hours.

Why does the number of flies in my HOTBIN seem to be increasing?

At the time of adding food waste into your HOTBIN, the eggs may not yet have hatched and so are not visible to the naked eye. If your HOTBIN is operating at temperatures of 20-25°C (i.e. it’s not quite reaching hot composting temperatures) the HOTBIN is creating the ambient environment for the eggs to hatch and for the larvae to mature into adults and consequently, their population will grow.  

How can I get rid of flies and maggots from my HOTBIN?

There are a number of preventative steps you can take to minimise the chances of finding flies in your HOTBIN:

      In the home you can:

  • Keep your food waste collection bins well covered to minimise the entry points and deprive them of a food source and breeding ground.
  • Ensure that any over ripe fruit is kept in the fridge or in the food waste collection bins so that flies do not infest the fruit – fruit flies in particular are attracted to the sweet sugars produced by the over ripe fruit.
  • Wipe up any spills on surfaces to remove any easy sources of food.

      In your HOTBIN you can:

  • Ensure your HOTBIN is operating between 40-60°C.
    • Evidence from the World Health Organisation has shown that fruit and housefly populations decrease at temperatures above 25°C and become undetectable at temperatures above 45°C. These hot composting temperatures, as well as helping to accelerate the decomposition process, also have the capability to destroy flies, larvae and eggs in the HOTBIN – so it’s win-win!
  • If you do have flies and/or maggots in your HOTBIN, you may need to check the temperature of your HOTBIN as they should not be able to survive above 40°C.         
    • A quick check of the ‘how do I get to 60C Check List’ might help detect the underlying cause of a cooler HOTBIN.
    • If, despite following the check list recommendations you are struggling to get your HOTBIN to reach 40°C, please email or phone the HOTBIN Team and we can help get you hot composting successfully.
  • Minimise the entry points to the HOTBIN by ensuring that the hatch and lid on the HOTBIN remain tightly closed and that the straps are in position (except when removing compost and adding new waste!)
  • Wipe the outside of your HOTBIN – a quick wipe over the area around the valve and the hatch can remove any residual odours or material and will further reduce the risk of attracting flies to the HOTBIN.

A note to the wise; contrary to some recommendations, the HOTBIN Team do not advise wrapping fruit and vegetable waste in newspaper before adding it to the HOTBIN. The newspaper will likely be visible in the final compost due to its high lignin content, will likely delay the onset of decomposition to the wrapped waste and may also block airflow around the HOTBIN, causing your bin to turn anaerobic.

Why have I got flies hovering around the valve and hatch panel?

Occasionally, you may find a number of flies hovering around the valve and/or the hatch panel, and unfortunately, there is not much that can be done to prevent this. They quite quickly will move away from the HOTBIN when they cannot find a food source or a place to lay their eggs.

How can I keep flies away from the outside of my HOTBIN?

If the flies are consistently hovering around the HOTBIN and they bother you, you may wish to look at using a fly/insect spray which can be sprayed around the HOTBIN to repel them. The problem is, of course that the HOTBIN usually lives outside and so as soon as it rains, the repellent will wash off!