Do Ants Help a Compost Pile?

A healthy compost pile is full of life; thousands of insects and millions of bacteria break down dead fruit, leaves, twigs, and other plant matter and convert them into a dark, crumbly, nutrient-dense black gold.

While some insects are obviously beneficial in a compost pile, ants fall into a gray area.

Ants will feed on insects (dead or alive), sugary plant matter, and honeydew, among other things. So, while they can help break down the material in a compost pile and clean up dead insects, they can also bore into compost bins and invade nearby garden beds.

The more complex answer is that the difference between ants being beneficial or harmful comes down to:

  • The ant species
  • The ingredients in the compost pile
  • The location of the compost pile
  • The type of compost bin

At the very least, ants in your compost pile are not an emergency, so don’t go spraying that beautiful pile of soil-building goodness with an insecticide until you’ve determined whether or not they pose a real problem.

Types of Ants in a Compost Pile

There are 12,000+ species of ants in the world, 700 of which are alive and well in the United States. However, there are only a few species of any significance that affect compost piles.

Carpenter Ants

  • Color: Brown, red, or black
  • Identification: Workers are wingless, and ¼”-½” long; reproductive ants have wings and are ¾” long
  • Habitat: Logs, stumps, hollow trees, homes
  • Region: All over the U.S.
  • Effect on a Compost Pile: Negative

Carpenter ants are attracted to the food in the compost pile and may burrow into wooden compost bins to create a nest around the food source.

It is a common misconception that carpenter ants eat wood. Ants prefer sugary or protein-rich food sources, not dense, fibrous material.

Carpenter ants burrow into wood to create nests and then discard the sawdust as they move through the material.

Carpenter ants prefer dark, damp wood-like rotting logs and tree trunks to build their colonies. However, they will set up camp anywhere near a good food source.

Imported Fire Ants

  • Color: Bright red or black
  • Identification: ⅛”-¼” long; wingless
  • Habitat: Lawns, against structures, against trees
  • Region: Southeast to Southwest
  • Effect on a Compost Pile: Negative

Fire ants pose a serious risk to your health, and their attraction to sweet ingredients and insects could cause them to take over your compost heap.

Fire ants are perhaps the most annoying and dangerous outdoor ant a gardener could encounter.

These little hellions are originally from South America. Like bees, most bites are mildly annoying for most people, but for anyone who is allergic to the venom, a few bites can be fatal.

Fire ants are the most aggressive ant species in the world, and they are spreading quickly across the country because there are few natural predators in the U.S. Swarms can be so aggressive; fire ants have been known to kill kittens.

Raspberry Crazy Ants

  • Color: Light red/brown
  • Identification: ⅛” long-winged males
  • Habitat: Under logs, rocks, and other debris
  • Region: Texas and surrounding area
  • Effect on a Compost Pile: Negative

Crazy ants will swarm food sources and drive away other insects and animals in the area

Crazy ants get their name from their erratic running habit while they are out foraging. These ants have no real central nest; rather, they live under wood, stones, and other landscape items or debris.

The crazy ant is so intrusive that many homeowners would rather have fire ants in their lawns than deal with this invasive, obnoxious species.

Crazy ants have been known to swarm areas so heavily that they will drive songbirds from their nests, cattle from their pastures, and pets from their lawns. These ants “farm” plant pests that produce honeydew, and they are such efficient farmers that they have destroyed grasslands in South America.

Turfgrass Ant/Cornfield Ant/Field Ant

  • Color: Light to dark brown or black
  • Identification: 1/10”-⅛” wingless workers
  • Habitat: Exposed soil and under logs, rocks, homes
  • Region: All over the U.S.
  • Effect on a Compost Pile: Positive

These small turf and landscape ants are an important part of soil ecology, and these ants are excellent for breaking down dead insects and plant matter.

Ants improve the soil as they make tunnels. Tunnels aerate the soil, introducing oxygen and preventing compaction.

The field ant builds small, harmless anthills in undisturbed soil and under landscape items. While these may become a tripping hazard or create a loose soil pocket, the hills are not a serious concern, and their bite is only slightly painful and annoying.

Field ants can invade homes in their search for food. While the ants are harmless (yet, annoying), they are frequently mistaken for carpenter ants, which can cause homeowners undue concern.

There are hundreds of other outdoor ant species, but most are harmless, like the field ant, and are no real cause for concern.

Ingredients in the Compost Pile

Ants are more likely to invade compost piles with sweet ingredients, like fruit scraps, and piles with lots of insect activity.

Insects are supposed to be in your compost heap- they’re one of the key players in the decomposition process. However, some insects can overrun a compost pile that is too heavy in one ingredient; like all things, balance is key.

Conventional wisdom says to avoid cooked foods, meats, and other processed items in your compost pile. Not only will they impede the composting process, but they also attract unwelcome guests.

Ants are far more likely to invade compost piles with forbidden ingredients as opposed to a balanced pile with fresh fruit and veggie scraps and lots of bulky, brown materials.

So, simply building a healthy compost pile will lessen the likelihood that harmful ants will invade your garden area, and increase the likelihood that beneficial ants will become part of a thriving ecosystem.

Location of the Compost Pile

Most ants are attracted to undisturbed soil, landscape items and debris, and dark, moist areas.

So, harmful ants are more likely to invade a compost pile when it is surrounded by piles of firewood, stacked next to a building, near a wooded area, or located in a dark, damp location.

Keep the area around your compost pile clear of debris and in an area with plenty of light and airflow. Not only will this prevent unwanted infestations, but it will also encourage quick, healthy decomposition.

If ants do invade your compost pile, the real risk is to the surrounding area. Ants won’t ruin a compost pile, but they will ruin wooden structures, vegetables and landscape plants, and possibly the surrounding ecosystem.

Ants Farming Aphids

One of an ant’s favorite food sources is honeydew. This sweet, sticky substance is a byproduct of sap-sucking pests like aphids.

Ants are so fond of honeydew that they will cultivate aphid populations to create honeydew. This process is called ant farming.

The problem with an ant infestation in the compost pile is the likelihood that ants will begin ant farming in your landscape or vegetable garden. Once they have built a large population in the compost pile, they can turn to cultivating pest populations to feed their growing army.

Home Invasions

While some ants can be harmful in the garden, all ants are unwelcome in the home.

Carpenter ants can invade wooden structures and compromise their integrity.

Crazy ants can disrupt the environment in your yard and even drive local animals from their habitats.

Fire ants can swarm unsuspecting feet and hands in the lawn or garden, causing painful and sometimes dangerous bites.

While most ant species are either harmless, if not mildly annoying, the harmful ones can be incredibly disruptive in the home and lawn area.

Worm Bins

Many ant species eat worms, so a worm bin could be in danger if it is located too close to a colony of fire ants, carpenter ants, or army ants.

Fruit scraps in a worm bin can attract initial worker ants, and prolonged use of sweet scraps may encourage a nearby ant colony.

So, if you’re wondering, will ants kill my compost worms? The answer is yes, but only if you’re trying to breed diabetic worms and not burying scraps consistently. Balance out the fruits with some good ol’ veggies, and you will make the worm bin much less attractive.

Compost Bin Materials

Obviously, wooden compost bins are much more likely to be compromised by ants than metal or plastic. They also tend to attract ants because they hold moisture and resemble dark, moist areas like dead logs or tree trunks where ants like to build a nest.

This doesn’t mean wooden compost bins are evil, but rather that they may be more attractive to ant colonies as they break down. Keep wooden bins in good condition and replace them once they begin to rot to prevent unwelcome insect activity.