Ants and Soil Bugs

While repotting my pothos recently, I discovered what looked like an entire civilization thriving in the drainage hole. There were ants, something with too many legs, and a bunch of tiny white specks that jumped when I poked the soil. My first thought was to throw the whole pot away and start over, but then I remembered how much I paid for that ceramic planter.

So I did what any normal person would do at 9 PM on a weeknight. I went down a research rabbit hole to figure out what was actually living in my plants and whether I needed to panic.

Turns out, not all soil bugs are bad. Some are actually helping your plants, and some are just minding their own business. But a few (like those ants I found) are a sign of a bigger problem. Here is what I learned.

Ants farming aphids

The ants in my pothos were not just lost. They were farming.

I know that sounds weird, but ants actually herd aphids like tiny livestock. Aphids are those soft-bodied insects that suck sap from plant stems and leaves. When they feed, they excrete a sweet substance called honeydew. Ants love this stuff. They protect the aphids from predators, move them to fresh feeding spots, and basically run a whole aphid ranch right on your plant.

According to research from the University of California Agriculture and Natural Resources, ants will defend aphid colonies aggressively because they depend on that honeydew. This means if you have ants crawling up and down your plant stems, you probably have aphids somewhere on the plant even if you have not spotted them yet.

I found my aphids on the underside of the leaves, which is their favorite hiding spot. They were pale green and clustered near the new growth. The ants had built a highway from the soil up the stem to reach them.

The problem with this setup is not just the ants. Aphids weaken your plant by draining its sap. They can also spread plant viruses. A few aphids are not the end of the world, but a whole colony protected by an ant army can do serious damage over time.

To deal with this, you need to break up the farm. I started by dealing with the aphids first. I took my plant to the sink and sprayed the leaves with water to knock off as many aphids as I could. Then I mixed a few drops of dish soap in a spray bottle with water and sprayed down the whole plant, focusing on the undersides of the leaves and the stems. The soap breaks down the aphids’ protective coating and they dry out.

For the ants, I had to find where they were coming from. In my case, they had a nest in the potting soil itself. I ended up repotting the plant in fresh soil and washing the roots to make sure I was not bringing any stragglers along. If your ants are just visiting from outside the pot, you can use a barrier like petroleum jelly around the rim to stop them from climbing in.

The key thing I learned is that ants in your plant pots are always a symptom of something else. They are not interested in the soil itself. They are there for the aphids, mealybugs, or scale insects that produce honeydew. Get rid of the sap-suckers and the ants will leave on their own.

Centipedes: Friend or Foe?

The long wiggly thing I saw in my pothos soil turned out to be a centipede. I am not going to lie, I screamed a little.

But after I calmed down and did some reading, I found out that centipedes are actually one of the good guys. They are predators. They eat other bugs that live in the soil, including fungus gnat larvae, springtails, and other small pests. A centipede in your pot is basically free pest control.

Centipedes are fast and they hide during the day, so you usually only see them when you are repotting or moving things around. They have a pair of legs on almost every body segment, which is how you tell them apart from millipedes. Millipedes have two pairs of legs per segment and they eat decaying plant matter, not other bugs.

According to the Penn State Extension, house centipedes and soil-dwelling centipedes are harmless to plants. They do not chew on roots or stems. They just hunt.

I decided to leave the centipede alone. It crawled off into the new soil when I repotted, and I have not seen it since. My thinking is that if it is eating fungus gnat larvae, it is earning its keep. I have had problems with fungus gnats before, and I would much rather have one centipede than a cloud of tiny flies every time I water.

The only downside is that centipedes can pinch if you handle them, but honestly, I am not planning to pick one up. If you are really uncomfortable with them, you can gently relocate them outside when you spot them. Just scoop them into a cup and take them to the garden. But if you can get over the creepy factor, they are doing you a favor.

Above: A close up look at the symptoms.

Earthworms in pots

I have never found an earthworm in my indoor plants, but I know people who have. It usually happens if you use garden soil or compost in your pots instead of sterile potting mix.

Earthworms are great for outdoor garden beds. They aerate the soil, break down organic matter, and their castings are an excellent fertilizer. But in a container, they can cause problems.

The issue is space. A potted plant has a fixed amount of soil, and earthworms need room to move and forage. In a small pot, they can compact the soil as they tunnel, which reduces airflow to the roots. According to the University of Illinois Extension, earthworms in containers can also cause drainage issues because their tunnels can channel water in uneven ways.

If you find an earthworm in your potted plant, the best thing to do is relocate it to your garden or a compost bin where it can actually thrive. Just dig gently around the root ball, pull out the worm, and move it outside. It will be happier, and your plant will drain better.

The other thing to watch for is that earthworms in your pots might mean your soil is staying too wet. Worms need moisture to survive, and if they are living in your container, it could be a sign you are overwatering. I learned this the hard way with a peace lily that I kept drowning. The soil was so soggy that I am surprised it did not sprout gills.

Springtails in soil

Those tiny white jumping specks I found in my pothos soil were springtails. When I first saw them, I thought they were some kind of mite or baby insect, but springtails are actually their own thing. They are soil-dwelling arthropods that feed on decaying organic matter, fungi, and algae.

Springtails are harmless to plants. They do not eat roots or living tissue. In fact, they help break down dead material in the soil, which makes nutrients available to your plant. According to research from the University of Minnesota Extension, springtails are common in potting soil that stays moist, and they are generally considered beneficial.

The reason they jump is because they have a spring-loaded appendage on their abdomen called a furcula. When they are startled, they release it and launch themselves into the air. It is kind of impressive for something the size of a pinhead.

I see springtails most often in my ferns and calatheas, which are plants that like consistently moist soil. If your soil dries out between waterings, you probably will not see them. They need that moisture to survive.

Some people freak out when they see springtails because they move fast and they are everywhere once you notice them. But I have learned to just leave them alone. They are not hurting anything. If the population gets really out of control, it usually means the soil is too wet or there is a lot of decaying matter in the pot. Letting the soil dry out a bit between waterings will reduce their numbers naturally.

If you really cannot stand them, you can repot the plant in fresh soil. But honestly, I think springtails are one of those things you just have to make peace with if you keep a lot of plants. They come with the territory.

Above: The tools you need to fix this.

Treating soil pests

Not everything in your soil is harmless. Fungus gnats, root aphids, and grubs can all damage your plants, and they need to be dealt with.

Fungus gnats are the ones I deal with most. They are tiny black flies that hover around your plants and lay eggs in moist soil. The larvae feed on organic matter and sometimes on root hairs, which can stunt your plant’s growth. I hate them because they fly into my face when I am watering.

The best treatment I have found is letting the top two inches of soil dry out completely between waterings. Fungus gnat larvae need moisture to survive, so drying out the soil breaks their life cycle. You can also use yellow sticky traps to catch the adults. I keep a few traps near my plant shelf and they fill up fast.

For serious infestations, I use mosquito bits. They contain a bacteria called Bacillus thuringiensis israelensis (BTI) that kills fungus gnat larvae but is safe for plants and pets. You can sprinkle the bits on top of the soil or soak them in water and use that to water your plants. The University of Wisconsin Extension recommends BTI as an effective and non-toxic treatment for fungus gnats.

Root aphids are harder to spot because they live underground. If your plant is wilting for no obvious reason and the soil looks fine, you might have root aphids. The only way to know for sure is to unpot the plant and check the roots. They look like tiny white or tan bugs clustered on the root hairs.

I have only dealt with root aphids once, and it was a nightmare. I ended up washing all the soil off the roots under running water, treating the plant with insecticidal soap, and repotting it in completely fresh soil. It took weeks for the plant to recover, but it did survive.

The best way to prevent soil pests is to use clean pots and fresh potting mix when you repot. I also avoid overwatering because most soil pests thrive in wet conditions. If you bring home a new plant, check it carefully before adding it to your collection. I quarantine new plants for a few weeks now because I have learned the hard way that pests spread fast.

One last thing I will mention is neem oil. A lot of people swear by it for treating pests, but I have had mixed results. It works okay for aphids and mealybugs on the leaves, but I have not found it very effective for soil pests. The smell also lingers forever, and my apartment is small.

If you are dealing with pests, start with the least toxic option and work your way up. Sometimes just adjusting your watering schedule or repotting in fresh soil is enough to solve the problem.

References

University of California Agriculture and Natural Resources. “Ants: Management Guidelines.” UC IPM Online. Accessed 2024.

Penn State Extension. “House Centipedes.” Penn State Department of Entomology. Accessed 2024.

University of Illinois Extension. “Container Gardening: Soil and Fertilizer.” University of Illinois Urbana-Champaign. Accessed 2024.

University of Minnesota Extension. “Springtails.” University of Minnesota Department of Entomology. Accessed 2024.

University of Wisconsin Extension. “Fungus Gnats as Houseplant and Indoor Pests.” University of Wisconsin-Madison. Accessed 2024.