How to identify common houseplant pests and treat them

Pests are a total nuisance when they attack our houseplants. If you don’t know what you’re looking for, then they’re especially evasive when it comes to identification, and it’s impossible to treat pests if you don’t know what you’re dealing with.

Thankfully, this article helps you identify common houseplant pests and treat them before things get out of hand. You can save your collection before pests eat it for lunch!

COMMON HOUSEPLANT PEST FAQS

I googled it, so you don’t have to!

How do houseplants get pests inside in the first place?

Keeping plants indoors means we open ourselves up to a partially closed environment, where pests find it easy to get in, but not out. They can be difficult to find because they often sneak in unnoticed and it’s only when we find damage, we realise they’ve been feasting on all our favourite plants for days or weeks.

Houseplant pests often make their way inside from outdoors, whether through open windows and doors, contaminated soil with eggs in, or just through transfer from humans or pets as we brush up against garden plants or grass. Be cautious when putting your plants outdoors in summer for a spot of sunshine – always check houseplants before bringing them back indoors.

What are the most common houseplant pests?

The most common houseplant pests are spidermites, fungus gnats, mealybugs, scale and thrips. In spring and summer, aphids also sometimes enter houses through open windows.

How do I know if my plant has pests?

Signs that your houseplant has pests include sticky residue on the leaves, discolouration of the leaves, thick webbing, or stunted growth. Houseplants that seem to be unhealthy but there’s no indication it’s anything else, could be affected by pests.

What’s the best way to prevent pests from entering my home?

Quarantining new plants is a great way to prevent houseplant pests from getting into the home. When you bring a new plant home, check it for pests and rinse it before it’s mixed with other houseplants. Keep new plants separate from existing houseplants to ensure they don’t pass pests if there’s a problem. 2-3 weeks is a safe time to acclimate your new houseplant.

Are houseplant pests dangerous to humans or pets?

Houseplant pests are generally not dangerous to humans or pets. Fungus gnats can be pretty annoying though and you may find yourself becoming a ninja at catching them. Beware of some pesticides and neem oil, which can be toxic to people and pets if ingested or inhaled. Always read the labels on products that you introduce to your home to reduce risk of harm from exposure. For more information about neem oil, head to the bottom of this article.

Do houseplant pests prefer some plants more than others?

It’s true that some houseplant pests prefer certain types of plant. For example, calatheas are known to be particularly delicious to spidermites. Velvety philodendrons also seem to attract thrips more than other types of plant. Plants that are already sick or unhealthy can attract houseplant pests more than healthy specimens. Houseplants with thick, waxy cuticles like sansevieria and ZZ plant tend to be more resistant to plant pests.

THE MOST COMMON HOUSEPLANT PESTS AND HOW TO GET RID OF THEM

Below is a list of the most common plant pests and how you can identify them from the damage they cause to your plants. And because identifying them isn’t enough to stop them from destroying your plants, I’ve included methods to tackle them too.

Fungus gnats

These pesky flies have a habit of flying around your living space, especially during autumn when the seasons change. Identifiable as tiny black or brown flies that look similar to fruit flies, you’ll visibly spot them hanging around houseplant soil, or buzzing uncomfortably close to your nostrils and eyes.

Fungus gnats lay their eggs in your houseplant soil, which then hatch and cause a breeding cycle to continue. The best way to deal with fungus gnats is to place yellow sticky traps in your plant pots. They may look unsightly, but traps are highly effective at catching these annoying little soil squatters. Overwatering can cause to overly damp compost that encourages fungus gnats to move in and start a family, so reduce how much you water your plants and only water when soil has fully dried out.

Thrips

Thrips are frequent aggressors when it comes to houseplant pests. As they’re between only 0.5-5mm long and usually brown or black in colour, they’re easy to miss when inspecting plants. In fact, it’s usually easier to see that there’s a problem due to the colour change of leaves to yellow.

Yellowing leaves with brown edges can be an indicator that thrips are feeding on the green chlorophyll in your houseplant leaves. It’s a good idea to take a closer look, but unless your eyesight is excellent, you may need a magnifying glass to spot them. Look for tiny brown dash-like marks on leaves or petite creamy-white rice-shaped blotches, which are thrip larvae.

Brown surface of variegated monstera deliciosa leaf, concurrent with thrip damage.

Treating thrips can be difficult because they’re so small, they can hide on stems and inside curled up emergent leaves. One way to eradicate them completely is to make a neem oil solution up. Add water, washing up liquid and neem oil. Mix it up in a spray can and spray your plants down. Alternatively, try a pesticide like provanto ultimate bug killer, which is extremely effective against thrips. This pesticide lasts for around 2 weeks, but is highly toxic to insects, people and pets if inhaled, so be sure to air out rooms afterwards.

Spidermites

Spidermites are possibly THE most annoying houseplant pests. They’re relentless with their attacks on plants and incredibly difficult to get rid of. They hide in the crevices of plants where they can’t be reached and can actually survive in soil for months. Signs you have spidermites include thick webbing around the leaves and petioles of your plants, and dappled discolouration on leaves. Spidermites are so small that they’re incredibly difficult to see without a magnifying glass. They are tiny white specks that crawl around leaves, often with red abdomens.

Spidermites often ride in on your plants from garden centres or plant stores and hang out in your house rent free, waiting for the opportune moment to strike. They can be present on your plants for months without you even knowing they’re there. The best way to prevent a spidermite break out is to wash all new plants when they enter your home and keep them apart from plants already in your collection. Keeping the humidity relatively high by misting plants or washing bi-weekly prevents spidermite outbreaks as they can’t breed as easily.

Fine webbing on a discoloured plant leaf, showing spidermites suspended.

If you’re facing a spidermite outbreak, ordinary pesticides won’t be effective as this type of houseplant pest is resistant to the majority of them. The best way to tackle spidermites is to adapt preventative measures and kill them by cleaning leaves with a special solution. One way of destroying spidermite is to use rubbing alcohol to wipe down your leaves. Alcohol breaks down a spidermite’s exterior membrane, causing death. Alternatively, wipe leaves with neem oil, washing up liquid and a hot water solution.

Scale insects

Scale insects are hard to see unless you get up close to your houseplant. Scale appears as miniscule brown bumps on stems and leaves, and unless you prod them, you won’t see them move. Scale feeds by piercing the plant tissue and sucking out sap, leading to weakened, yellowing foliage and long term, stunted growth. When scale insects are present, the sticky honeydew left behind may look like globules of liquid on leaves and stems.

The best way to remove scale insects is to soak a microfibre cloth with rubbing alcohol and wipe the leaves and stems of your houseplant with it. Pay special attention to areas with an abundance of brown bumps – if these are scale, they’ll start to fall off. Treat affected houseplants regularly and inspect them closely, as scale insects can be persistent and difficult to eradicate entirely.

Mealy Bugs

Despite sounding cute, mealy bugs can be pretty destructive and difficult to get rid of. Easy to spot because of their white, fluffy appearance, mealy bugs cluster like cotton wool on houseplant stems and the underside of leaves. Mealy bugs can cause leaves to go yellow and wilt, and in extreme cases, you may see black spots of sooty mould as the honeydew escaping through nibble marks gets infected. Mealy bugs can spread easily, so make sure you isolate affected plants until you’ve solved the problem.

The most effective way to get rid of mealy bugs is to remove them using a cotton bud or microfibre cloth soaked in rubbing alcohol. Gently wipe the affected areas of your houseplant to kill them on contact. For persistent infestations, you’ll need to repeat the process weekly. Alternatively, use a neem oil solution on mealy bugs – mix neem oil with water and a few drops of washing up liquid and spray or wipe onto your houseplant.

NEEM OIL AND HOW TO USE IT SAFELY

Neem oil is an excellent method of eradicating soft-bodied pests like thrips, spidermites, scale, mealybugs and aphids. It is a natural extract from the bark of a non-native tree and has been proven effective as an insecticide. It works by coating insects in an oily exterior that can lead to suffocation. The active ingredient is azadirachtin and causes insects to stop reproducing and feeding. Neem oil solution acts as a repellent and needs to be reapplied every few days.

Neem oil is still a controversial product in UK horticulture because if not used responsibly, it can be damaging to the environment. However, neem oil can be used responsibly and safely indoors as an effective method of control against pests that are resistant to pesticides, such as spidermites. Neem oil is not recommended for outside use because it can be harmful to bees and other insects. Be especially careful with over-exposing people and pets to the smell of neem oil, because its long-term effects haven’t been well researched.

To use neem oil as an insecticide, fill a bottle with 10% neem oil, a squeeze of washing up liquid, and top up with warm water. You can spray directly onto leaves or wipe it on with a microfibre cloth to get in all the hard-to-reach areas.