Houseplant pests are inevitable, and thrips are some of the worst! Here’s how to get rid of thrips inside the house and save your precious plants.
How to get rid of thrips inside the house & save your plants
If you’re a houseplant lover, you’ve probably heard of thrips. They are demon pests from houseplant hell, and when they move in to your plants, you’re in for the fight of your life. If I sound dramatic, it’s because I’m on the tail end of a battle with thrips on my big beloved monstera deliciosa. And those thrips also spread to at least one other plant, meaning it turned in to an all-out war.
But I’m getting ahead of myself. If you suspect your plant has thrips, you might be wondering, what are thrips? Where do they come from? Are my other plants infected? How do I get rid of thrips inside the house? What did I do to deserve this, I am such a good plant parent? Me too. So let’s cover it all.
What are thrips?
Aside from just being total aholes, thrips are very small and sadly somewhat common pests that can be found in houseplants and outdoor gardens. There are thousands of different thrips species, but thrips generally are teeny tiny insects with wings—though they jump more than they really fly.
Thrips take up residence on your plant because they think it’s delicious. They destroy plants by feeding on them and sucking the life out of them, literally. Female thrips lay their eggs in plant tissue, and one of the reasons they are so hard to control is that they do not need males to reproduce. Thrips have no need for men. And they are using their powers for evil instead of good.
Thrips will go dormant in the winter. In the spring when it starts warming up, females lay their eggs—lots of them. They only take a few days to hatch if the weather is warm enough. The thrips lifecycle from egg to adult can take 1–2 weeks, and then adult thrips can live for 7 or so weeks. All of this is important because it helps explain why it’s so hard to get rid of them.
The little hatched thrips babies are larvae and crawl around like pathetic little life suckers feeding on your plants sap. It’s highly unlikely that you’ll ever see then at this stage because they are so small. Eventually they begin to grow into the prepupal phase and then pupal.
Many thrips then drop into the soil (because they don’t have their dumb wings yet) to develop into their adult form. The adults then emerge, buzz up to the plant, and start the process all over again! Oh, and the adults feed like kids in a candy shop while they’re at it.
Signs of thrips on houseplants
Signs of thrips on your houseplants can look a lot like some other pest infestations: discoloration on the leaves (brown, grayish, sometimes yellowish), and leaves that grow distorted. One way to help narrow it down is if you see damage that looks like pests, but you can’t actually find any pests.
Thrips are tiny and can move or jump quickly, meaning you might miss them without a keen eye. But you might see small black spots about the size of a pin’s head near damaged spots. This is thrips poop. Yep, they eat your plant and then leave their poop as thanks.
Before I found the first adult on my monstera, I saw some minor yellowish discoloration and black spots on the undersides of the leaves. I also noticed some mildly deformed edges on the plant’s new growth and some smaller brown spots in the areas where the stems meet the leaves.
Once I saw this, I checked the plant, not totally sure of what was going on, until I found my first teeny tiny crawler. I went to poke it and it bounced away—the thrips bounce! Remember, they have wings but suck at flying. This is when I began losing my mind—hopefully I can save you some of that.
Where do thrips come from?
Generally, when you find thrips on one of your houseplants, they came home with another plant. Based on what I’ve been able to find about the plants thrips like and based on the timing my issues started, I suspect thrips hitched a ride into my home on a monstera adansonii cutting.
I learned my lesson the hard way about the need to isolate new plants for a few weeks before introducing them to other plants. If I would have done that, I probably would have caught the signs of thrips early, and they wouldn’t have spread. The plant ended up dying, but looking back, the signs were all that of thrips. And I had it right by my big monstera 🙁
Around this time I also had some curious damage on my rhaphidophora tetrasperma (mini monstera), which was also a relatively new plant to the bunch. This could have also been patient zero. It doesn’t matter now, all that matters is that I am more careful going forward! (Spider mites can also hitch rides in on new plants—learn how to spot and get rid of spider mites.)
How to get rid of thrips inside on houseplants: My monstera deliciosa
Once I was reasonably certain that my monstera had thrips, I sprung into action. I am going to summarize all of the steps I took to isolate and treat the plant, including what worked and what didn’t.
The first step: Isolate the plant
Thrips will spread, and they are pretty effective at doing so and multiplying. So the very first thing I did was isolate my monstera. We don’t have a big house, so there isn’t a ton of room for a large plant that also gets decent light.
So I did a bit of rearranging and moved it to the other side of the room. Knowing that thrips aren’t super effective fliers, I felt that this was ok. I didn’t have a ton of options though, and if I could have moved it to a completely isolated room, I would have done that.
Next step: Inspect other plants
Next I took a look at all of the plants that had been around my monstera to look for signs that the thrips had spread. I have A LOT of plants, and many of them are very close together, so I was having panicked thoughts by this point. I decided to treat any plant that had and small sign of damage, as well as any plant that was by the monstera.
Unfortunately this was quite a few. But I decided it was best to treat them all instead of risking it. I didn’t have any fears of the treatments hurting the plants. I was mostly worried about a major infestation. So my first try was using neem oil.
Begin treatment using neem oil
I really don’t like the smell of neem oil, so whenever I use it, I try to use it in well-ventilated areas or outdoors. I even sometimes put on a mask, which lots of people should have handy these days. To get started, I sprayed down my entire monstera top to bottom. Including the undersides of leaves. Until the entire thing was dripping. I did this two weeks in a row.
This was a pain because I had to drag my giant monstera out to the deck and fill my tub with the smaller plants, but it was the easiest way to do it. I checked my plants daily. After a few weeks, I noticed some more signs of thrips—the poops spots, and eventually, some adults. Damnit!
If you are early on in a thrips infestation, neem oil can be effective. That’s because it works by smothering adult thrips and adding somewhat of a repellant later on your leaves afterward. However, neem oil alone probably won’t do the trick.
Remember how thrips drop to the soil to finish their journey to adulthood? Gotta tackle those too. I also read mixed reviews about whether neem is even effective at controlling adult thrips, and since I still had a problem, I was ready to try something else. To make matters worse, I spotted an adult on my rhaphidophora tetrasperma, so it was time for war.
Next up: Captain Jack’s Dead Bug Brew spray and spinosad
The name itself gave me hope, but so did the active ingredient: spinosad (.001% in the ready-to-use concentrate). Spinosad is a natural substance that comes from bacteria in soil. It is an effective insecticide when used as a topical spray. It works in a few days when insects ingest it or even touch it.
I picked up a bottle of ready-to-use dead bug brew spray at Home Depot and went to town on my monstera, tops and bottoms of the leaves, spraying until it was dripping. Since the neem oil didn’t work, I also opted to treat every plant within a few feet of the monstera. Needless to say, I needed to buy another bottle.
While I was hopeful that this would work, I knew now that I needed to take more aggressive action to combat the longer thrips lifecycle. So I continued to spray my plants roughly once a week with dead bug brew, either outside or in my tub. Then I moved below the surface of the soil…
Systemic granules for long-term protection using imidacloprid
I decided to use Bonide systemic houseplant insect control granules for plants that I had either seen thrips on or seen any damage on. Just to be sure. The nice thing about the systemic control granules is that they protect your plants for up to 2 months. The active ingredient is Imidacloprid.
To use this insecticide, you put the appropriate amount (based on the size of the pot and plant) into the top 1–2 inches of soil. When you water the plant, the imidacloprid is released into the soil and root system. The plant then absorbs it, and it spreads throughout the plant.
This doesn’t hurt the plant, but it sure hurts the insects that try to eat parts of your plant! It damages their nervous systems, eventually killing them. I feel like this is really grim…like nerve agent stuff…but let’s remember who we’re fighting here. THRIPS.
My ultimate thrips solution: Systemic granules, dead bug brew, and insecticidal soap
By this point, I was edging up on fall and would have a harder time dragging my big monstera out onto the deck to treat. It doesn’t like the cold, and I didn’t want to pull it outside, even briefly. So I decided to roll with the systemic granules, dead bug brew, and insecticidal soap as backup.
About 6 or so weeks after applying the first round of systemic granules, I added a second round to my plants. I temporarily ceased any bottom watering so I could ensure the granules could do their job.
Knowing that I was looking at 8 weeks for a total thrip life—potentially longer if I wanted to be careful—I ultimately decided to alternate weeks with the dead bug brew (spinosad) and the Bonide’s insecticidal soap spray (Potassium laurate). I used Bonide Insecticidal Soap, but anything with Potassium laurate or “fatty acids” will work. It is just another way to kill thrips on contact.
So…did you get rid of the thrips?
As of writing this post…yes! Which I feel like I shouldn’t even say, because one could be lurking in there under the surface, waiting to pop up and lay all of its eggs again and start the vicious cycle. But I have not noticed any new damage, and the new growth on my plants looks healthy and properly formed.
I’m going to keep some of my fly traps around the suspect plants to help catch adult thrips if they ever return. These are good for fungus gnats too, so no harm done there. They are cheap and easy, and they work great.
I will continue checking my plants for issues and update this post if necessary. I really hope I don’t have to…it’s been a few months of battling them now, and I really want to say that I’ve won!
Other things you might try to get rid of thrips inside
In my research, I came across a couple of other things you can try to get rid of thrips inside the house or on houseplants. I didn’t try these, but you better believe I will if I have to one day!
- Pyrethrin spray. Pyrethrin comes from chrysanthemum flowers. It attacks insects’ nervous systems, leading. to death by paralysis. Check out what Safer Brand has to say about it.
- BotaniGard ES contains a fungus that attacks pests. The insects ingest it, and then the fungus grows inside of them, eventually killing them. The imagery in that one is fun. You can apply it weekly; read more here.
- Beneficial insects. This would be high on my list if my thrips were on outdoor plants. Beneficial insects feed on thrips eggs and larvae. Some examples include minute pirate bugs, thrips predator (the actual name!), ladybugs, and lacewing. Check out options and pricing here.
And that ends the world’s longest post on the world’s tiniest bastard of a bug. Can you tell I have strong feelings about thrips? 🙂 I really hope it helped you if you’re facing a thrips infestation!