The Houseplant Person’s Guide to Thrips

Thrips are the worst of houseplant pests, for one reason, and one reason only: they become immune to *almost* every method of removing them.

If you want an easy method to get rid of thrips that they won’t become immune to, get predatory mites.

I know it’s icky, but trust me, every other method of thrips elimination is either incredibly tedious or will stop working.

What are thrips?

Thrips are insects that eat your plants.

There are around 7,700 different species, but most of them eat fungus. There are a few that eat plants and they’re the ones we’re discussing in this article.

Thrips reproduce asexually and lay about 100 eggs in one go, so one single thrips can quickly become an infestation.

Thrips also spread diseases, but that’s not really a problem in the houseplant industry.

Thrips lifecycle

1. The thrips will bite a hole in the leaf and lay an egg into it
2. The egg will hatch into a first instar larva, that will eat plant matter
3. The larva will then turn into a second instar larva (bigger than the first). It will continue eating your plant
4. The larvae will turn into a prepupa. They live on leaves and in the soil, but don’t eat
5. The prepupa will turn into a pupa, again living but not eating on the leaves and soil
6. The adult thrips will emerge

There's not really a lot of point explaining the length of the thrips lifecycle. 

It's around 45 days, so you need to keep up treatment for at least that long BUT the problem with thrips is that there can be several thrips at different stages of the lifecycle all on your plant at the same time

I'm not saying this to freak you out - more to point out that learning this stuff isn't particularly useful/important.

Where do houseplant thrips come from?

Adult thrips can fly – kind of. So they can come from anywhere.

Ok, they can’t really fly, but they have wings, so they have controlled movement in the air, but are mainly propelled by air movement.

Thrips are most likely to come from two places:

• New plants that you brought home
• Blown in through the window, or on your clothes, hair, etc.

Though there are some steps you should take when bringing new plants into your home, there is no reasonable way to completely eliminate the chance of you getting thrips.

Thrips are incredibly common, and it’s better than you arm yourself with the knowledge of how to get rid of them, rather than just hoping they’ll never be a problem.

Most houseplant people will encounter thrips at some point. Thrips infestations aren’t a sign that you’re a bad houseplant person. They’re wily critters.

How to identify thrips

Thrips identification is important. Adult thrips can jump quickly, like fleas, so try to familiarise yourself with what thrips damage looks like as well as the adults.

What do thrips look look like?

Adult thrips look like long, thin… bugs. They jump quickly but are quite slow-moving the rest of the time.

They’re usually black or brown, but I’ve also seen some yellow/pale brown ones, which IMO opinion are more difficult to see.

The larvae are also easy to identify – they look like tiny yellow/pale green worms:

What does thrips damage look like?

Thrips damage varies, depending on the plants. On the anthurium clarinerveum in the picture above, there isn’t that much visible damage, because the leaves are so thick. The physical signs the plant shows are smaller leaves, and slower growth.

You might also see their poop, which looks like brown spots on the leaves:

You might also see damage to the leaf, for example, white patches where the chlorophyll has been sucked out

As someone on Instagram pointed out, it looks like the thrips tried to write ‘hi’ on my Alcoasia dragonscale.

Sometimes thrips damage looks like someone attacked your plants with an eraser:

Another sign of thrips is when new leaves just brown off and die before unfurling. It can be a root problem, but I always check for thrips when I see this:

Thrips can also kill the leaves of smaller plants, before you even realising that you had a problem. This Philodendron squamiferum will be ok, but the leaves are toast:

Some leaves might unfurl ok, but be stunted and weird, like on this Pothos Njoy:

This begonia goes black from the centre when there are thrips present. She’s actually my early-warning thrips beacon:

You might notice sticky sap on thrips-infested plants. Plants release sap when they’re under attack from pests. We actually don’t really know why, but the general theory is that it attracts ants, which will force the thrips to retreat.

Whatever the reason, they’re not much use in houseplants, other than as an early sign of possible infestation.

How to check a houseplant for thrips

So now you know what you’re looking for, and you think you’ve found some evidence of thrips activity, you might want to look for the actual culprits.

I’m so accustomed to seeing thrips damage that I don’t even look for them any more. As soon as I start seeing stunted grow and funky leaves I get straight on to treating them.

But if you want to look for thrips themselves, this is how I check for pests:

• New growth first – thrips love it because it’s easy for them to eat
• then check the backs of the leaves, at the top where the petiole joins the leaf
• Then check the fronts

There are also plant-specific places they like to hang out. They love to hang out in the petiolar sheath of Monstera deliciosa, and on the backs of Anthurium clarinerveum, where the two lobes of the leaf meet each other at the back.

I have a more detailed article on checking houseplants for pests here.

Which houseplants do thrips like best?

I don’t think there’s a universal list of plants thrips like – it will vary from house to house.

In my experience, thrips LOVE Monstera deliciosa, Anthurium clarinerveum, and Ctenathe lubbersiana. Not only are they hard to shake from these plants, the plants can host them for a long time without suffering damage.

They also seem to love (and do a lot of damage to):

• Monstera peru – they hide in the ribs and can reduce it to a pot of soil and stems in weeks
• Begonia – again, the plant will be ok but the leaves will be toast
• Pothos Njoy – tbf these things are the sickly members of the Pothos family in my experience

The only plants I’ve known that don’t fall victim to thrips are peace lilies.

How to prevent thrips on houseplants

Prevent possibly isn’t the right word here, because it’s impossible to 100% prevent thrips BUT you can make them a LOT easier to deal with by both creating an inhospitable environment AND improving your plant’s ability to fend them off.

Thrips aren’t deterred by environmental conditions like adverse humidity and temperature. They’re incredibly adept at adapting to different conditions so you can’t reduce numbers by increasing humidity like you can with spider mites.

There are, however, things you can do:

Keep your houseplants healthy

It sounds obvious, but there’s a difference between plants being alive and plants thriving.

• Move anything that’s in low light. It will need extra energy to fight off thrips
• If it’s cold, try grow lights, heat pads, or terrariums to bring the temperature up to comfortable levels for your plants.
• Make sure the roots are healthy. Your plant needs to be able to concentrate on fighting one battle at a time

Keep your houseplants dust-free

Not only do thrips love dust (so do spider mites. Weirdos) but a layer of dust on your plants will block out the light and block the stomata. Both of these things reduce the plant’s ability to photosynthesis and therefore feed itself. Low-energy plants struggle to fend off houseplant pests such as thrips.

Clean your houseplants with neem oil

When you clean your houseplants, dust them, then spray them down with neem oil diluted in water. Neem oil affects thrips’ ability to reproduce and eat, so they’ll die off over time.

Isolate any new houseplants

The most likely way of introducing thrips into your houseplants is bringing in new plants. Make sure that you keep your new plants in a separate room for a month or so.

Supplement your plants with silica

Adding silica to your water as a regular part of your houseplant care regime can strengthen the walls of your plant leaves, so the thrips have to really work hard to bite through them. They’ll struggle to feed properly and will therefore:

• be more likely to go elsewhere or
• be easier to eradicate

Further reading:

• How to clean houseplants
• How to use silica on houseplants

How to get rid of thrips on houseplants

This probably isn’t an exhaustive list, and everyone has preferences about what they like to use.

Thrips will become resilient to specific products over time, so be prepared to switch things up over time.

Predatory mites

I know they’re gross. I know it sounds counterintuitive.

But predatory mites are the easiest way to get rid of thrips that actually work. You cannot become immune to someone eating you.

The only downside is that they can be expensive. I got rid of thrips off about 20 plants with £12.99 (inc P&P) worth of amblyseius swirskii.

I SWEAR you won’t notice them. They’re teeny tiny. It’s actually incredible that they manage to eat the larvae, which are considerably bigger than them.

The only issue is that they don’t kill the adults, but they’re pretty easy to see and squish.

You can actually set up subscriptions, so that as the predators die, new ones turn up.

If you’ve had it with treating thrips, using predatory mites is such a low-effort/high-reward method. It takes ten minutes to spread the mites (they come in vermiculite-like stuff) onto the leaves and then you just let them get on with it.

Blue sticky traps

Blue sticky traps are a great way to stop thrips moving from plant to plant. They’ll only catch the adults, so I wouldn’t advise ONLY using blue sticky traps, but they can be a good extra step. They’re a physical trap, so obvs thrips can’t become immune BUT I wouldn’t be surprised if they stop loving blue so much in a couple of generations.

Diatomaceous earth

Diatomaceous earth can be sprinkled on top of the soil to stop the adults emerging from the pupa.

Again, this isn’t something that will stop an infestation on its own – most pupa are on the lower leaves, and diatomaceous earth only works when it’s dry BUT it has the additional benefit of releasing silica into the soil when it does inevitably get watered in.

Neem oil

Neem oil CAN work but you need to regularly clean your plants with it and it works better as a preventative as it can take a few weeks to work.

Some people have reported that neem oil burns their leaves. It’s not something I’ve experienced, but be sure to dry your plant’s leaves off to reduce the chance of burning.

Insecticidal soap

Insectidical soap is my go-to for initial infestations. It kills thrips on contact because it inhibits both eating and breathing. Add a drop of castile soap to a spray bottle of water and spray your plants thoroughly a couple of times a week.

Don’t try to up the dosage – you only need a drop, and excessive use will cause damage.

Systemic insecticides

These are the go to of TONNES of people. I can’t use them because they’re banned in the UK, but a lot of Americans swear by them.

You water in the granules, and the plant absorbs them. The plant matter becomes toxic to thrips.

Topical pesticides

Provanto is popular in the UK and Europe, and Captain Jack’s is popular in the US.

Thrips can become immune to these products, and they’re not great to use long-term. They can cause damage to mammals of all species, so make sure you use a mask and use outdoors if possible. The active ingredients are spinosad and deltamethrin, which kill insects and…aren’t great for us.

I’m obviously not saying don’t use them. If they were that dangerous they wouldn’t be available BUT they do a lot of harm to beneficial insects and I…prefer to use other things. Especially when thrips become immune anyway.

Water bath

Waterbaths are AWESOME at getting rid of thrips (and most other pests) but in reality are a PITA.

You have to soak your plant for 10 mins in water that remains a consistent 45˚C/113˚F. This is difficult enough (unless you have a bain marie) but you also need to keep the soil as dry as possible.

Great in theory, but not in practice.

Regular showering

I’ve had a lot of success with just regularly hosing my plants down. I use the sprayer nozzle on my kitchen tap because it’s pretty easy to water the plant but keep the soil quite dry.

The only issue is that you need to be VERY consistent for months, and…I get bored/forget.

Hydrogen peroxide

Hydrogen peroxide can be used for both getting rid of pupa in the soil and spraying the leaves down.

In my experience, using hydrogen peroxide DOES work on treating thrips, but only if you have small numbers. It’s something I might use once just to see if i can quell an infestation with one round of treatment. It won’t do much to a full-on thrips assault.

Further reading:

• Using predatory mites on houseplants
• Using hydrogen peroxide on houseplants
• Using diatomaceous earth on houseplants

Things that WON’T eliminate thrips

Just so you don’t waste your time!

Treating plants once or twice

Occasionally, if you’ve timed it right, you can knock thrips out in one fell swoop, but it’s VERY rare. Even if you don’t treat, check your plants regularly for at least six weeks after treating them.

Cinnamon

Cinnamon is a very mild fungicide, that won’t faze thrips at all. Probably just makes the plants tastier.

Hoping they’ll go away by themselves

Yeah, no, they won’t.

Cold weather

Thrips overwinter very well. They’re actually more likely to turn up in winter because houseplants are weaker and less able to fight them off.

Ok, that’s all I know about thrips. If you have any tips or secrets to thrips elimination, I’d love to read about them in the comments.

Before you go, you might like these articles:

• How to get rid of thrips on Monstera deliciosa
• Does LECA reduce pests?
• Houseplant Pest Guide