Ok – you’ve started your worm farm for vermicompost, worm tea, worm castings, to do your part against global warming, to provide bait for fishing – or whatever. But suddenly things start going wrong! Pests can be a big problem. So lets roll up our sleeves and get our hands dirty as we look at some ways to prevent pests from ruining your worm bed.

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Protecting Your Worm Bed (prevention is better than cure)

The best way to handle worm farm pests is to ensure that they don’t establish themselves in the first place. Therefore it is best to keep your worm beds well maintained by ensuring that:

  • Your bin lid or farm enclosure is secure.
  • The worms and bedding are covered with either a sheet of plastic or a damp sheet of burlap (Hessian).
  • Food scraps are covered with bedding to prevent them becoming mouldy and attracting pests.
  • No meat, greasy food, or pet faeces is included in the feed as these attract flies – therefore maggots – and possibly even rats, which can literally gnaw their way into plastic bins.

For continuous worm farming, it is recommended that you house your worm bin, or other worm farming medium, in enclosed places such as: garages, sheds, basements or out-buildings; therefore making them less accessible to pests. It would also be helpful to screen the buildings as will help limit your losses to rodents, birds, mammals, snakes and most of the larger earthworm pests. Of course, screens and gratings placed at the top and bottom of the beds can also be effective, but you can never have too many lines of defence. A sheet of Mosquito netting draped over your bins would eliminate most flying pests and is little hassle to use.

Two Worm farms with mosquito nets to stop flying pests



How to Deal with Worm Composting Pests

All of the following creatures pose a threat to earthworms: ants, mites, slugs, raccoons, springtails, rats, moles, amphibians, reptiles, gophers, certain beetle larvae, maggots, and a variety of other insects. Fortunately, most of these villains can be neutralised by properly constructed bins, screening, or – most importantly – good worm bed management. Nonetheless, we’ll take a closer look at some our beloved worm’s greatest enemies and what can be done about them.



Watch out for ants as they can wreck your beds in a matter of days and therefore require immediate action. Ants are attracted to the feed, so don’t spill any near your bins and clear away any old spillage as soon as it is spotted. If your bin isn’t too big and has legs, another way to keep ants out is to put each of your bin’s legs in a dish of water – alternatively, most of the garden centres sell ant goo – a sticky substance that is painted around the stems of rose bushes to trap ants. It is eco friendly as it doesn’t contain any insectide poisons.

If all else fails and  the ant invasion has already become serious, you can dust the area around your beds with pyrethrum dust or douse the ant nest and the trails leading to your bin with a granular insecticide, or use commercially available ant traps, which contain slow release poisons that the ants take with them back into their nests. Please be sure not to use any insecticide on the actual worm bed soil or you will kill your worms. If ants are already established inside the beds soak the section they are in and they will usually go away.



Infestation of mites in a worm farm


These tiny creatures do not actually harm your worms, but are unsightly and do compete with the worms for available food.

Most worm beds usually contain several species of mites (the most important for, our purposes, being the earthworm mite), which pose no real threat to the worms unless their population spirals too high – this usually happens as a result of poor bed management. Earthworm mites are small and are usually brown, reddish or somewhere in-between. They tend to concentrate near the edges and surfaces of the worm beds and around clusters of feed. They are not known for attacking the earthworms but do eat the earthworms feed. When the mite population is too high the worms will burrow deep into the beds and not come to the surface to feed, which hampers worm reproduction and growth. High mite populations usually result from: –

  • Over-feeding. Maintaining a proper feeding schedule (for example: one that ensures the feed is eaten in a few days) will prevent the feed from going off in the beds.


  • Feeding the earthworms meaty or wet feed. Large mite populations are often the result of using over moist garbage and vegetable refuse as feed. Adding the occasional soggy vegetable leftover probably won’t cause a problem but don’t make a habit of it.


  • Over-watering. A rule of thumb when watering is to keep the beds damp but not wet. Poor bed drainage can also facilitate a mite problem and make the beds less hospitable to worms. Ensure that there are adequate drainage holes at the bottom of your worm bin or housing.

Remember the same conditions that ensure high worm production will be less favourable to mites. If you find your worm farm overrun by mites, expose the beds to the sun for a few hours. Cut back on water and feed and then, every 1 to 3 days, add calcium carbonate. Another method is to over water the bed forcing the mites to the surface and then burning them with a blowtorch. Both of these methods though are only short-term remedies and eventually you will have to improve the conditions in your worm farm if you want to keep the mite population low.

Fruit Flies

These insects will be attracted by over ripe fruit and certain vegetable scraps. They lay their eggs in the decaying fruit, but are not really a major problem. Just make sure that you cover any fruit with some of the bedding. A jam jar that has a residue of sticky jam/ jello or marmalade smeared around its sides can be half filled with water and left beside the worm bin. The fruitflies are pretty stupid and get stuck to the jam or drowned in the water. I personally don’t like to use commercial insectides, but fruit farmers often use ripe fruit bait that has been poisoned to attract and kill the fruitflies – I suppose its one step better than spraying the actual fruit that we are going to eat.


Blow Flies and House Flies

Excess flies buzzing around your worm bins or worm farms are usually the result of having used meat, greasy food waste, or pet faeces as feed. They spread disease and make life miserable for the worm farmer and his family. They can also result in maggots if the beds aren’t properly sealed. If your farm is kept indoors or under some sort of shading – as it should be – then you can hang up some fly strips, which will draw them away from the farms. Again, a properly maintained worm farm will normally not stink and therefore not attract flies.


Black Soldier Fly

Latin Name: Hermetia illucens. It is a moot point as to whether this fly should actually be called a pest. It is a tropical fly, originally from the Americas, that has now spread around the world. The larvae of the fly are a type of small maggots, that feed exclusively on putrescent material. They are often found in worm farm bins, but although unsightly are not a real threat to the worms, as they do not attack them and may in fact complement the compost worm’s activities, rather than compete with them for food. Like the vermiculture worms their faeces make excellent compost and the maggots are also useful  as a high protein fish or poultry feed and may be used either live or dried, as a processed meal. They may also be used by the less squeamish for fish bait. They can best be kept out of the worm farm bins, by not using meat and fatty waste and by keeping the moisture on the dry side, and making sure that there is a good cover of  bedding material over the feeding area.

These remarkable creatures, unlike the common housefly, do not spread bacteria or disease – in fact the larvae ingest potentially pathogenic material and disease-causing organisms and thus render them harmless. Moreover black soldier flies exude an odour, which positively discourages houseflies and certain other flying pests. When the larvae reach maturity they  leave the feeding area  to pupate, preferably  in a shady bush or tree. After turning into an adult fly, the female lives a further 5-8 days and produces almost 1000 eggs. The adult fly is nocturnal and characterised by very fast and rather clumsy flight. It has no mouth and cannot bite or sting.

There is a growing interest in using Black Soldier Fly for commercial processing of sewage and agricultural waste. Some hobbyists have been experimenting with the Black Soldier Fly, as an alternative to vermiculture, for for private composting/ waste disposal. For the same size of container it is said that a well stocked colony of Black Soldier Fly would be able to process waste material very much faster than a comparable sized worm farm.



These wingless oblong insects live on decaying and sometimes living plant matter and are a sub-class Apterygota. You can recognise them because they jump when disturbed and can turn a worm bed surface white if the population is large enough. Although they have on occasion been observed to eat dead or weak worms, they are primarily a nuisance because they eat the worm’s food and can, when the populations are big enough, drive the worms deep into the beds and keep them from coming to the surface to feed. One deals with them the same way one deals with mites.