Aphid-Eating Ants: Are They Real Or Not?

by | Ants, Aphids, Insects

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If you’re seeing ants and aphids on your plants or trees, you’re probably wondering if the ants are there to eat the aphids. Well…

Ants farm and take care of aphids because aphids give ants food. But ants will eat aphids when other food is scarce, there are too many aphids for the farm, to control the types of aphids on the farm, or when an aphid is sick or not making enough food for the ants.

Ants and aphids have a rather fascinating relationship. Let’s take a closer look at what ants really do with aphids, how ants and aphids kill and harm your plants, and how to get rid of them both once and for all.

Are ants eating aphids in your yard?

Black ant drinking honeydew from an aphid

If you have ants and aphids on your plants, it might look like the ants are there to feast on the aphids.

The truth is that ants do go out looking for aphids. But when they find aphids, the ants work to keep the aphids alive and healthy rather than killing or eating them.

Aphids may be tiny scale insects, but they have powerful mouths that can pierce a plant’s stem and leaves. Once in, the aphids suck sap from the plant for food and can kill your plant.

When an aphid pierces a plant, sap runs into its body. Aphids turn this sap into a sweet, sticky liquid called honeydew, which they excrete through their anus.

Ants love honeydew, and they protect and care for aphids so they have a constant supply of this honeydew.

When ants eat aphids

Ants will kill aphids and feed them to their young only when:

The ants need food for their young

Adult ants cannot eat solid foods, but their young need proteins and fats to grow up strong and healthy.

If ants cannot find enough high-quality food to feed their young, they will kill and use aphids as a food source.

There are too many young aphids to look after

Aphids feed on the sap in a plant, but the plant can only feed so many aphids before dying. This is why it’s important for aphids to control their numbers in a colony.

When an aphid colony gets too big, the females give birth to young aphids with wings. Within a few days these winged aphids are big enough to fly off and find a new plant to live on, where they start a new aphid colony.

But ants have another solution to control the aphid population on the farm: The ants chew off the wings of young aphids to stop them from flying off. And they simply kill some aphids if there are too many aphids for the plant to feed.

Young aphids don’t have the right characteristics

Closeup photo showing an ant aphid farm and different colored aphids

Ants are very particular about what they want in the aphids they keep.

Some ants want certain color combinations in the aphids they farm, and they will kill the wrong color aphids until they get the right balance of color in the colony.

Ants also keep the strongest young aphids alive, which are the ones that make the most honeydew. The ants kill off any weak or unproductive young aphids.

Older aphids don’t make enough honeydew

When aphids get older, they often cannot make as much honeydew as they did when they were younger.

When an aphid isn’t making enough honeydew to keep the ants happy, they will kill it and probably feed the aphid to their young.

An aphid gets sick

Any aphids that get sick or show signs of illness are removed from the farm and killed by the ants.

This is how ants make sure that the aphids stay healthy, and that no diseases are spread through the aphid colony.

Why ants and aphids are bad for plants

Aphids are bad for plants. Ants don’t damage plants or eat plant leaves, but they farm aphids by protecting them from predators and taking care of them. This makes the combination of ants and aphids deadly to many plants.

Here are five ways that ants and aphids harm your plants:

Ants and aphids kill plants

Aphids take plant sap from plants. This plant sap is called phloem (FLOW-m), and it carries energy and hormones from the leaves to the plant’s stem and roots.

Ants encourage aphids to collect a lot of sap from the plant to make honeydew, and the ants kill off any aphids that aren’t producing enough honeydew. In this way, ants increase the amount of sap that aphids would normally remove from plants.

When the aphids drink a lot of sap, the plant doesn’t get enough nutrients and may stop growing and eventually die.

Ants and aphids cause plant deformities

Closeup photo showing deformed green ash leaves from an aphid infestation
Source: With thanks to Steven Katovich, Bugwood.org

Aphids and ants steal nutrients from the plant to feed themselves, so the plant cannot grow as it should.

An affected plant will often start showing abnormalities in its leaves, stem, flowers, and fruits. For example, the leaves may turn yellow, or start curling.

Ants and aphids make plants sick

Because aphids drink the nutrient-rich sap from plants to feed the ants, plants don’t have what they need to stay healthy and strong.

These plants become weak and unhealthy. This makes it easy for bacteria, viruses, and pests to attack the plants and kill them.

Ants and aphids cause sooty mold

Aphids make a lot of honeydew, especially when ants only keep the aphids that can produce a lot of this sweet substance.

As a result, excess honeydew often drops down onto the plant’s branches and leaves.

Over time, a fungus known as sooty mold grows on the honeydew and turns the area black.

Sooty mold stops sunlight from reaching that area of the plant, and if enough of the plant is covered in sooty mold, it becomes weak.

Aphids may cause abnormal plant growths

When a plant is irritated by a pest, such as aphids, it can get abnormal growths on its leaves, flowers, branches, or roots. These growths are called galls, and they look like little bumps or irregular bulges.

Galls do not harm the plant, but they are a sign that the ants’ aphid farm is overstimulating and disturbing the plant’s peace.

How to get rid of ants and aphids

If you want to stop ants from farming aphids in your yard, you need to take steps to get rid of both of these insects.

Here are some things you can try to get rid of aphids and ants in your yard, to see what works best for you:

To get rid of aphids:

  • Inspect your plants and trees regularly for signs of aphid infestation: aphids are usually found on flower buds and growing tips. As soon as you see any aphids, put gloves on and pick off all the aphids by hand. Throw them into a bucket of soapy water to kill them.
  • Use a hand sprayer and spray plants with a strong spray of tap water, to knock aphids off.
  • Wash plants, especially indoor plants, with soapy water once a week. Here are instructions on how to make an effective soapy spray with Dawn dish soap.
  • Put this food-grade diatomaceous earth from Amazon on the plant’s leaves and around the base of the plant, wherever you think the aphids will cross. This cuts the aphids and kills them, but be careful because it can also kill beneficial bugs such as these ground bee pollinators that come into contact with it. It’s best to use this method when your plants are not blooming.
  • Use this Neem oil spray or this insecticidal soap spray from Amazon on your plants, to keep kill aphids on contact.
  • Grow plants in your yard that aphids hate, such as marigolds, garlic, onions, leeks, chives, cilantro, and catnip.
  • Remove plants that attract aphids, such as asters, mustard, begonias, cosmos, nasturtiums, sunflowers, and dahlias. Or, alternatively, use these as trap plants to attract aphids so you can kill them.
  • If a branch is heavily infested with aphids and you cannot seem to kill them off, cut off the branch. This is better than letting the aphids harm or kill the plant over time.
  • Attract aphids’ natural predators to your yard, like lacewings and ladybugs, but remember that the ants will try to kill these predators if they attack the aphids. There is a list of natural predators in the next section of this post.
  • Cut banana peels into pieces and bury these in the soil around the plants that aphids are attacking.
  • In winter, when aphid eggs are hiding in the bark of your fruit and shade trees, spray the trees with dormant horticultural oil to kill the eggs.

To get rid of ants:

  • Spray the ants with this Dawn dish soap spray, to kill them on contact (it kills the aphids at the same time). However, this only kills the ants you see. There are many more ants in the nest and they may soon arrive to start a new aphid farm.
  • Place these ant bait traps from Amazon around the plants that are being used to farm aphids or around the ants’ nest, if you can find it. The ants will carry the poisonous bait into their nest for the colony to eat and die. This can be much more effective at getting rid of ants.
  • Put this diatomaceous earth from Amazon on the plant’s leaves and around the base of the plant, wherever you think the ants will cross. This kills them, but it can also kill beneficial bugs. It’s best to use this method when your plants are not flowering.

What eats aphids

Aphids have many natural enemies. If these predators are welcome in your yard, and the ants don’t attack and kill them, they are very useful in keeping aphids (and other plant-destroying insects) under control.

Here is a list of what eats aphids:

  • Ambush bugs
  • Aphid wasps
  • Assassin bugs
  • Big-eyed bugs
  • Birds, such as warblers, finches, and hummingbirds
  • Damsel bugs
  • Earwigs
  • Hornets
  • Hoverfly larvae
  • Lacewings
  • Ladybugs / ladybirds / ladybeetles
  • Long-legged flies
  • Midges
  • Paper wasps
  • Parasitic wasps (here are all the pests that wasps will eat in your yard)
  • Pirate bugs
  • Soft-winged flower beetle
  • Soldier beetles
  • Spiders
  • Syrphid / flower / hover flies
  • Yellowjackets / wasps

Source: Adapted, with thanks, from Utah State University and several other sources

The following video shows how the ants protect the aphids from predators, but there’s a wasp that doesn’t want to give up. Does he get an aphid meal, or do the ants win?

I'm Monique. I love gardening and spending time in my backyard growing things. Here's where I share what I know about backyard pests and what to do about them, so you can enjoy your yard too.

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Monique loves gardening and spending time in her backyard, where she grows flowers, succulents, herbs, fruits, and vegetables.

Monique spends a lot of time researching how to protect her backyard from harmful pests and trying to attract beneficial insects and animals.

She shares everything that she learns and tests here at Backyard Pests.


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