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How to Identify and Control Houseplant Pests

About Houseplant Pests

Pest attacks are much more common outdoors in the garden, but even the most experienced houseplant owner will still fall victim to an attack indoors from time to time. Don't worry though. We're going to share our experience and knowledge to help you easily sort out pest problems.

This is how to deal with common indoor plant pests, insects and bugs

This article will show you how to deal with all these pests and more

The trick is to be observant of your houseplants and then when you notice there's a problem, act decisively and quickly. If you follow this rule your plants have a much better chance of making it out of the battlefield with minimal or no lasting damage.

Organic vs. Chemical Control

Where possible we'd suggest giving the eco-friendly method for pest eradication and control a go first. Because let's face it, none of us need to be spraying chemicals around our home unless we really have to.

But the truth is that having plants indoors severely limits or completely removes the option to use truly organic pest control, for example outside Aphids will eventually be eaten by ladybugs. So while we detail an organic method, we also list a chemical option where appropriate.

The Common Pests

The most common pests are listed below, along with their identifying symptoms and suggested treatments. If you're having problems with something different, let us know in the comments and we (or other readers) will try and help you out.

Close up photo of a Red Spider Mite on a plant leaf

Close up photo of a Red Spider Mite on a plant leaf

Just before we get on, let's quickly point out that sometimes your plant will have a disease rather than a pest problem - in which case you'll need to head over to our disease page.

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Aphids / Greenfly / Blackfly

Aphids suck sap usually from the new soft plant growth, the tips, flowers etc, however they can attack any part of the plant. Normally hidden from obvious sight, i.e. under the leaves, they are typically green, but can also be black or grey and arrive in small, but quickly reproducing colonies. They can be seen easily with the human eye if you look closely.

A ZZ Plant under attach by sap sucking Aphids

Aphid infestation

Symptoms

They tend to mass together in large numbers making them easy to spot and identify. Look for sticky honeydew deposits on the plant and their white or grey "husks" littering the soil and sticking to the honeydew. Long term affected plants may become infected with disease or viruses, the leaves may also turn yellow in random patches. Growth may also become distorted.

Treatment

Control is really easy and in most cases doesn't require anything more than warm soapy water although theoretically a chemical treatment, in comparison to others it's very gentle.

  • One - You can reduce the numbers (or any strays) by simply squashing them with your fingers. If there are lots or you are too squeamish to do this then move to the following steps.
  • Two - Fill a spray mister with warm water and a small amount of liquid soap or washing up liquid. There should be enough that if you shake the bottle it foams up.
  • Three - Spray the plant liberally with the solution, make sure you target the Aphids themselves so this may involve moving the bottle or plant into different positions to reach everything. It's important you do this, because Aphids must be covered in the solution for it to work.
  • Four - Most plants don't mind the occasional drench of soapy water, but if you don't want to risk it, hold the plant sideways as you are spraying or cover the soil to reduce the amount of liquid that soaks in.
  • Five - Wait five minutes before washing off the soapy mixture as best as you can. You can also water the plant well at this point to flush out any mixture that may have soaked into the soil (make sure you have drainage holes!).
  • Six - Sometimes one treatment is enough, but you may have to repeat it again a few weeks later.
  • Chemical: If you need something stronger look for permethrin, pyrethrin, or neem oil containing products. Be careful if using chemical sprays on Ferns as they can be very sensitive.

Centipedes / Millipedes

Centipedes and Millipedes are normally beneficial insects, especially when living outside in the garden. Centipedes will often hunt smaller insets and other pests. Whereas Millipedes will eat organic matter like dropped leaves which helps break it down and helps turn the matter into useful nutrients for growing plants. But inside they can be worrying and disturbing to see.

Sometimes described as "worms with legs" or "worm bugs" it's not too uncommon to run across these critters from time to time. Very occasionally you might get an "infestation" as shown below.

Large number of Centipedes and Millipedes on the soil surface of a houseplant

When Centipedes or Millipedes show up in high numbers it can be a shock to see

Symptoms

They rarely do any damage to your plants, so you're only likely to notice their presence when you literally spot them with your eyes as they're crawling about. Normally they're more active after you disturb the soil, such as when you water it.

Treatment

  • Organic: The above picture is quite a rare example. You're much more likely just to find a couple at most and when you do it's easy enough to pick them out of the soil and re-home them outside.
  • Organic: If you have a large number present, or you keep finding more even after picking them out and removing them, more drastic action might be needed. In these cases we'd recommend repotting your plant, knocking off as much of the old soil from around the roots as possible. Repot your plant using fresh potting soil / mix.
  • Chemical: Using chemicals here is extreme considering these bugs are easily treated organically. But if needed, grab a bucket and fill it with warm (not hot) water and liquid soap. You should then dunk the entire root ball of the plant (you can leave it in its pot if there are drainage holes at the bottom that water can soak up into) until fully submerged.

    Leave it to soak for half an hour then remove it and give the soil a good rinse to try and wash out some of the suds. The insects will have either drowned or been killed by the chemicals within the soap.

Mealybugs

Mealybugs are related to Scale insects and cause damage by sucking sap from plants. They are reasonably large as far as pests go, resembling furry white woodlice. They cluster together and at first glance, you might think you are looking at cotton wool. If left untreated their damage will cause the leaves of the plant to yellow and eventually drop off.

Mealybugs attacking the underside of a plant leaf

Mealybugs attacking the underside of a plant leaf

Symptoms

It's very common to be able to spot the insects before you start noticing symptoms on the plant, colonies of mealybugs tend to group on the undersides of leaves and in the leaf joints of plants. The plant will show you it is infested by wilting and generally looking dehydrated, it may be losing leaves quite rapidly. Also, look for sticky honeydew residue.

Treatment

  • Organic: You can often knock them off the plant with a shake, poke or spraying them with water.
  • Chemical: If the infestation is quite large follow the Aphid treatment technique.
  • Chemical: Use products containing natural fatty acids or those formulated with a surfactant.

Red Spider Mites

Of all the house plant pests you can come across the Red Spider Mite is arguably the most feared. The damage caused isn't necessarily the worst, but their prevalence and difficultly in removing can be quite trying and frustrating.

Like their name suggests they're arachnids and therefore related to normal spiders, however although they spin webs all over your plants they don't feed on flies, instead they eat the liquids found within plant leaves. The webbing is used to protect the colony and basically open up quick access "roads" to different parts of the plant, if allowed to get out of hand you will have a mini-metropolis on your hands.

Red Spider Mite's spinning webs over a houseplant

Red Spider Mite's spinning webs over a houseplant

Symptoms

The sticky webbing is one of the most obvious signs these insects have set up home. However the most common symptom on the plant is mottled leaves with lots of little brown dots. This is caused by the spiders piercing the leaf cells with their mouthparts which then causes the cells they've pierced to die and in turn creates this brown speckling effect.

Treatment

  • Organic: These mites hate water and humid conditions. It can take a while to completely remove the pests, but if you pop your plant in the shower each week and give it a tepid shower you will help to wash off the webbing and gradually reduce the spider mite numbers. During the days between showers, mist the plant daily to help increase humidity. Check our Humidity Guide for other ideas you might like to try.
  • Organic: If multiple plants are affected, or you live in an area where they are a regular problem (perhaps also with your garden or yard plants) it might be worth purchasing the predatory mite Phytosieulus persimilis. They feed on Red spider mites and will quickly outnumber them if temperatures are above 18°C (64°F).
  • Chemical: Use products containing natural fatty acids or those formulated with a surfactant.

Scale Insects

Scale is a tricky pest to identify and can be difficult to eradicate. The insects have a hard outer brown shell that locks them in place a bit like barnacles on a beach at low tide. They are neatly camouflaged because even if you are looking at them directly to the untrained eye you may still think you are looking at a natural blemish on the plant leaf.

Scale Insects sucking sap from an Umbrella Plant

Scale Insects sucking sap from an Umbrella Plant

Symptoms

Quite simply, sticky honeydew everywhere. If the plant is near a window it will be filthy with it, if near fabric the honeydew will eventually turn black and create almost "sooty" like mould. Look closely at the underside of the leaves or on the stems and you will see them as small round or oblong brown discs.

Treatment

They are only formidable because of their protective shield, if you can get rid of that then you've almost won the battle already. Although it's rare to eradicate them in one go. Their offspring are very small and mobile therefore easy to miss, in a few weeks they will set up home where their parents once lived. Be prepared to treat the plant several times before they go completely.

  • Organic: If you have a small number you can pick or rub the scales to kill them.
  • Organic - Dab individual scales with alcohol. This basically dissolves them.
  • Chemical: The Aphid spray method detailed above works well in softening the discs. After about five minutes you can pretty much wipe them off with a damp cloth.
  • Chemical: If you need something stronger look for permethrin, derris (banned in many countries due to human health concerns) or malathion containing products. Be careful if using chemical sprays on Ferns as they can be very sensitive so use only as a last resort.

Sciarid flies / Fungus gnats

There is nothing worse than having small annoying files zipping around. You bat them away to start with, but with their constant distraction you seek out where they are coming from and eventually find a small colony hovering or running around the base of your houseplant(s).

Without doubt, this is the most common pest in our house. Fortunately although also very common for a lot of other owners they tend not to harm indoor plants and are therefore more of a nuisance than anything.

Close up photo of a Fungus Gnat / Sciarid Fly

Close up photo of a Fungus Gnat / Sciarid Fly

Symptoms

Spotting small black flies around 2mm long either flying around near the plant, or running over the soil surface. The larvae are small worm-like creatures, up to 1cm long and thin, it's hard to spot them though as they tend to exist just under the soil surface.

Treatment

  • Organic: These pests need organic matter to feed off and moist upper soil conditions. Make sure you pick off any fallen plant material and try keeping the soil less moist until they leave. A good tip is to use the Bottom Watering Method, as long as you don't overwater this should help keep the soil surface drier and reduce the Fungus Gnat population.
  • Organic: Nematodes have become increasingly popular ways to deal with pests and they also work well with Sciarid Flies. Nematodes are microscopic worms that seek out larval stages of various fly and other diptera insects that develop in plant soils.

    To treat a plant all you basically need to do is mix the nematodes with water to "activate" them and then water directly into the affected pot. They eat the larva which in turn breaks the cycle and within a few weeks no more Fungus Gnats.
Sciarid Fly Killer on Amazon.com

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Sciarid Fly Killer on Amazon.co.uk

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  • Chemical: Pyrethroids and Pyrethrin containing products can give some control. If the adults have already laid eggs in the soil before spraying, the larva will still emerge in a few weeks and you'll need to treat again.

Slugs / Snails

In 95% of cases, you'll only have Slug or Snail problems on plants that you choose to put outside in the warmer months of the year, they can still set up shop in your home too though. They are quite a big pest both in size and with the amount of damage they do in a short space of time, however they're also the simplest to deal with.

Slugs and Snails can eat and damage entire sections of plants in a single night

Slugs and Snails can eat and damage large sections of plants in a single night

Symptoms

Identification is easy. The leaves will be drastically damaged, large holes, or entire leaves stripped clean.

When morning comes they'll already be well hidden away after feasting on your beloved plants, But they will sometimes leave a slimy trail around the area, which is the smoking gun as to what the culprits are.

Treatment

  • Organic: If the plants are outdoors the easiest solution is to put them in a protected place. High up etc. Slugs and Snails have strong homing instincts returning to the same areas night after night, so another idea is to move the plant to a different place entirely.
  • Organic: Indoors / Outdoors, if you go on a "dusk pick" when they start to become active again you may catch them in the act and can therefore move them far away.
  • Organic / Chemical: If you have it in you, then you can also kill them. Either with a large boot or with slug pellets. As with all pests however they do play a vital role in the natural cycle of things, in particular making a delicious meal for birds and small animals like hedgehogs. So if you can't bring yourself to kill them something else will do the job for you eventually.

Springtails

Springtails are small, white or grey insects that live off the decaying organic matter found in soils. They are small (although can be seen easily with the human eye as they stand out against the dark compost) and best resemble fleas, they aren't really pests at all as they do no damage. However their presence often attracts attention because when you water and are consequently paying more attention to the plant than usual, the water triggers the Springtails to go wild with movement and thereby alerting you to their existence.

Springtails living on the soil surface of a houseplant

Springtails living on the soil surface of a houseplant

Symptoms

When you water the plant and it hits the soil, you'll notice small white flea like insects jumping or moving around.

Treatment

As above there isn't a need for a "treatment", but they can be frustrating if you want to get rid.

  • Organic: The simplest way to reduce numbers and give control is, where possible, water your plants less. Springtails need water to survive and if there isn't any their numbers will eventually decline. You have to be careful though as not many plants will survive long periods without water!

Thrips

Saving the worst to last perhaps. In our experience Thrips or "Thunder Flies" are the stuff of nightmares when it comes to houseplant pests. They can significantly damage and disfigure plant foliage in a short space of time and if left untreated will kill your plant. A mild infestation completely took out two Monstera plants and a large Palour palm before we even knew what was happening.

Only a few houseplants are truly resistant (or unattractive to them) and Thrips will spread around your home to other plants if given the opportunity.

They're also difficult to get rid of unless you're persistent. Treat them seriously and eradicate them if possible. If you've tried the treatments below and still think you're losing the battle, throw your plant away. Often it's not worth the risk of them spreading to the others in your collection. Hoover, and thoroughly clean around the area the plant was growing before you put a replacement there.

Thrips showing the damage they can cause to houseplants

Thrips can ravage a houseplant quickly. This once used to be a handsome Parlour Palm. It's now sitting on top of the compost heap.

Symptoms

Thrips, in particular their larvae, are hard to spot. They often live on the underside of leaves and tend to have similar colors to the underside of the leaf, so easily blend in. In the photo above you can just see two or three of them towards the center-right of the picture. Sort of look like dust don't they? They hardly seem a threat at all. Don't underestimate them is my advice.

It's far more common to notice mottling, streaking, browning or yellowing on the leaves of your houseplant. It's easy to think the damage is some kind of watering problem. When overwatered, the leaves on most houseplants will quickly go a solid bright yellow. So if you have something in between do spend five minutes just checking the leaves to make sure it's not Thrips (or something else).

Treatment

  • Organic: In the early days the larvae could be contained to just a small section of your plant. Carefully (as you don't want them falling off onto the healthy leaves) cut off and remove the leaves or infected flowers. Get rid of the removed bits from your home as soon as possible and take potential cross-contamination seriously.
  • Chemical: Organic sprays, such as natural pyrethrum or neem oil can help. You may have to apply them several times over a few weeks. Make sure you spray all of the plant including the top of the soil.
  • Chemical: If the organic sprays aren't working you'll need to consider the more persistent contact-action or systemic insecticide products such as those containing pyrethrin, lambda-cyhalothrin or deltamethrin. The insecticide effects last for longer, but take care with their use and ensure you follow the manufacturer stated instructions.


About the Author

Tom Knight

Tom Knight

Over the last 20 years Tom has successfully owned hundreds of houseplants and is always happy to share knowledge and lend his horticulture skills to those in need. He is the main content writer for the Team.

Also on Ourhouseplants.com

Photo credit of the Red Spider Mite close up Gilles San Martin
Photo credit of the Mealybug Forest & Kim Starr
Photo credit of the Red Spider Mite Harald Hubich
Photo credit of the Fungus Gnat Erik Burton
Photo credit of the Springtails Marshal Hedin


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