Why Is My Compost Pile Full Of Ants? (Answered and Explained)

It is not unusual to find a colony of ants has made your compost pile their home. Wherever in the world you live, ants are commonplace, and there are many species of ants, as well as other bugs, that find compost piles to their liking.

Compost bins and piles provide the perfect habitat for a colony of ants. The contents of the pile provide a steady source of food, the heat from the pile decaying offer the ants warmth, even in the winter, and more often than not our compost piles are covered, providing the ant colony protection from the worst of the weather.

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Are Ants Bad For a Compost Pile?

No, ants are not bad for a compost pile, in fact, having a colony of ants in your compost can be extremely beneficial. It is estimated that there are over 1,000 species of ants in the United States and many more around the world. Only a small handful of these species are considered a pest.

Ants, along with many of the other bugs we find living in our compost piles, actually help the composting process. At a tiny level, ants break down some of the fruit, vegetables, and plant matter we place in our compost piles and help the micro-organisms do their job of breaking down the compost pile even further.

What are the Benefits of Ants in a Compost Pile?

Ants shred waste

Ants use their mouths to cut tiny pieces from leaves, fruit, and other vegetation before they take it back to the heart of their nest to feed the colony. At a tiny level, this shredding of the contents of the compost pile helps the heap to break down faster.

Whatever you place in your compost pile, the smaller it is, the quicker it will break down. Ants in your compost pile help facilitate this process. For many years I have practiced running an old mower over my garden waste to break it down as much as possible before adding it to my compost pile.

Ants aid aeration of the heap

As the ants move through the compost pile, they create hundreds of tiny tunnels. These tunnels allow air to flow right into the heap.

Good bacteria within our compost piles, that’s the bacteria that helps the heap breakdown without giving off a horrible smell, require oxygen to live. The tunnels created by the ants bring fresh oxygen into your compost heap.

The ants’ tunnels also aid drainage of excess moisture which can often build up in a compost pile when we add too much material that is high in moisture such as grass clippings, fruit, and tea bags.

Ants help mix the compost heap

If you have ever added a whole load of one type of material to a compost pile, you will no doubt have noticed it didn’t break down very well. For composting to be successful it needs a real mixture of ingredients.

Having ants in your compost pile helps with this mixing, all be it at a small level. As the ants spread throughout your heap in search of food, they cut up and take material from one area and move it to another.

Ants move bacteria and fungi around the heap

Bacteria and fungi are the lifeblood of our compost heaps. These microscopic creatures do most of the hard work when it comes to breaking down the material we place in our compost bins.

As the ants move around our compost piles, they naturally move the bacteria, both on their feet and bodies as they move around, and also whilst moving the bits of waste they have cut up for food.

Although both bacteria and fungi seem to find their way to all parts of the heap eventually, ants no doubt speed up the process.

Ants are micro predators

Ants don’t just eat vegetable matter, they as true omnivores, they will also consume meat in the form of other bugs that live in our compost piles.

Whilst it is true they will eat some of the other beneficial creatures, they also eat many of the harmful ones too. A heap with a healthy colony of ants will often be free of pests such as wasps.

Having ants in the compost bin make the whole pile a slightly safer place when it comes to digging the finished compost into our gardens.


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Which Species of Ants Are Bad For A Compost Pile?

According to Ehrlich Pest Control, there are around 8 species of ant that are considered a pest and should be actively discouraged from your compost pile or their colonies destroyed if you find them in your heap.

The table below lists the 8 species and gives a short description of what they look like.

NameDescription
Argentine Ant (Linepithema humile)Length: 1/16″ – 1/4″
Color: Dark brown to black and shiny
Black house ant (Ochetellus)Length: 1/16”
Color: Typically jet black
Carpenter ant (Camponotus pennsylvanicus)Length: 5/8″
Color: Red, black, or a combination
Red imported fire ant (solenopsis invicta)Length: ⅛”-⅜”
Color: dark reddish-brown
Southern fire ant (solenopis xyloni)Length: ⅛”-⅜”
Color: dark reddish brown
Ghost ant (Tapinoma melanocephalum)Length: about 1/16”
Color: Pale/translucent legs and abdomen with a dark brown head and thorax
Odorous house ant (Tapinoma sessile)Length: 1/16″ – 1/8″
Color: Brown or black
Pavement ant (Tetramorium caespitum)Length: 1/8″
Color: Dark brown or blackish

How to Discourage Ants From a Compost Pile?

There may be occasions when, despite the benefits ants can bring to a compost heap, you decide you want to discourage the ants, or get rid of a colony in your heap.

There are a number of different ways to discourgae ants. Some are organic gardening friendly and others are not. Essentially the method you choose is a matter of personal choice.

Raise the temperature

The warmer the compost pile, the less hospitable it is to ants. As compost breaks down, the bacteria that are doing the majority of the work give off a lot of heat. A well-constructed heap can easily reach 170°F (77°C).

Ants naturally choose to live at a much cooler temperature, so if you keep your heap warm, not only will you have fewer pest ants, but your compost material will decay much faster.



Add more moisture

The vast majority of ant species prefer to live in dry conditions rather than wet ones. The more moisture you add to your compost pile, the less likely ants are to try and colonize the pile.

A word of caution, a compost pile benefits from moisture, but like everything, too much is bad. If you make your compost pile too wet, the good (aerobic) bacteria won’t have access to sufficient oxygen, and the bad (anaerobic) bacteria will take over, leaving you with a slimy, smelly compost pile that breaks down very slowly.

The material in a compost pile should be moist, but not wet. When you squeeze a handful it should roughly have the consistency of a damp sponge, not a dripping wet one!

Turn the heap on a regular basis

Ants go to a lot of trouble to build their colonies. For such tiny creatures, they can shift an awful lot of material, but it takes time.

One great way to discourage ants is to turn your whole compost heap on a regular basis. I try to turn my piles once a week for the first month, then roughly once a month for the next 6 to 8 months.

In my experience, turning the heap so regularly has the added benefit of discouraging other pests, such as rats, and also mixing the material thoroughly, which speeds up the whole composting process.

How to Get Rid of an Ants Nest in a Compost Pile?

If you find you have one of the ‘pest’ species of ants, or you simply decide you don’t want the ants in your compost bin anymore, there are a number fo steps you can take to rid yourself of the ants.

Pour cold water on the nest

If you expose the colony of ants, try to find where the eggs, and ideally the queen, are. If you can locate them, pour a watering can of ice cold water over them. This sudden chilling will kill the ants, the queen and the developing eggs.

Use Boric Acid

According to Ants.com, Boric Acid is essentially poison for ants. It impacts their stomachs, their nervous systems, and their exoskeletons.

To rid yourself of an ant colony using Boric Acid, first, order yourself a small quantity of Boric Acid (I recently bought this pack from Amazon). Next, mix about one cup of food with 3/4 tsp of Boric Acid. Common foods to use include sugar water, honey, jelly, peanut butter, regular butter, or bacon grease. Finally, place the food/acid mix clise to the colony and wait for the ants to take it back to their colony.

Using Boric Acid to destroy an ant colony is not a quick process. It may take weeks or even months for the colony to die off completely, but it is a relatively cheap method that doesn’t require a great effort from the homesteader.

Crushed limestone

If you ever go to the trouble of testing the pH of your compost pile (not something I do on a regular basis), the chances are you would find it was on the acidic side.

This is exactly the environment ants like. By adding lots of crushed lime to the pile, you will bring the pH back towards neutral and make the pile in general less attractive to ants.

Diatomaceous earth

Diatomaceous earth is not only a cheap way to control ant populations, it is also non toxic and completely safe to use around children and pets.

When mixed into the compost pile, the Diatomaceous earth sticks to the ants feet and legs and also gets into their exoskeleton and joints. Some sources also state that the relatively sharp nature of Diatomaceous earth means it scratches and cut the ants as they move through it, leading to moisture loss from their bodies and eventually death.

I have tried Diatomaceous earth to good effect in the past, and if your compost pile is relatively small, it is worth a try.

Cornmeal

Cornmeal is an excellent way to kill off an ant colony, although it is not an especially fast method.

Sprinkle the cornmeal liberally around the ant colony. Once the ants discover the cornmeal they will quickly take it back to their colony to eat. Unforuntely for the ants they can not digest cornmeal and they will die.

Vinegar

To make a spray that will rid your compost pile of ants, mix three parts white distilled vinegar with one part water. Pour this mixture into a spray bottle and spray anywhere you see the ants. Repeat spray every day and you will soon find you no longer have an ant colony in your compost pile.



Chemical Control

Whilst chemical control is never my immediate go to method of controlling ants, there may be occasions when you decide chemical control is the appropriate way forward.

Pyrethrum insecticide is widely recognised as the most effective way to kill ants. Simply spray it around your compost heap, especially where the ants are and the ants will die on contact.