Updated on May 17, 2023
There are a lot of common pests out there that have become notorious for infesting houseplants. Aphids, mealybugs, scale insects, spider mites, and whiteflies are some of the habitual offenders ones out there.
But one common pest doesn’t seem to get as much attention as the others. These pests are tiny little insects known as thrips, and they’re one critter you definitely don’t want in your home or garden. Keep reading to learn what will get rid of them and won’t.
Getting to Know Thrips
Evolution is a crazy thing sometimes, and thrips have adapted in some very unique ways. Let’s take a few moments to look at thrips in general.
What Are Thrips?
Thrips are insects belonging to the order Thysanoptera. At less than 2/5th of an inch long, they can be hard to spot until you have a large infestation. However, there are approximately 6,000 species, most of which are classified as piercing insects (just like aphids and mealybugs).
A few are predator species, but the chances of a thrip in your home being the predatory type are pretty small.
These insects have a thin, roughly cylindrical body and fringed wings. A curious feature is that their mouthparts are asymmetrical. The right mandible is smaller and may not even exist. Meanwhile, the left mandible is used to slice open a plant so that saliva can be injected. The partially digested plant material is then sucked out of the plant.
While technically the word thrips is both singular and plural, you will sometimes hear people refer to a single thrips as a thrip. The name itself literally means “woodworm” in Greek, and this critter has picked up a lot of additional nicknames over the years.
Some of these names include: corn fleas, corn flies, corn lice, freckle bugs, harvest bugs, physopods, storm bugs, storm flies, thunderblights, thunderbugs, and thunderflies.
Can Thrips Fly?
Thrips fly about as well as bricks – meaning they can be lobbed over short distances, but gravity soon wins out. Their wings instead use a rare method to propel the bug. Known as “clap and fling”, this method of flight is very unwieldy and thus thrips are unable to sustain an elegant flight path like many other flying insects.
But there are also many wingless species out there that might give you the impression they can fly. As with many insects this small, gravity doesn’t have as much effect as with larger critters and a stiff breeze can yank thrips off of their perch and send them through the air.
What Attracts Thrips
Environmental conditions play a huge role in whether you’re at high risk of thrips invading, as well as some surprising factors. For example, we’ve mentioned before that bedbugs are attracted to certain colors, and the same is true of thrips.
They’re highly attracted to yellow, making many repellent plants such as marigolds ineffective. White and blue are also attractions for thrips, and most light colors can stimulate their presence to a smaller extent.
Moisture is another thing that can draw thrips, and it’s not unusual for these critters to wander inside in search of warmth and humidity. They also prefer young or tender leaves, unripe fruit, and are more likely to gather around plants that are in enclosed spaces, such as a densely packed garden.
What Damage Do Thrips Do?
A large infestation of thrips can dehydrate plants, causing the leaves to lose chlorophyll and eventually die. In some cases, they’ll simply dry out in patches, while in others they can become necrotic or become infected by fungal disease.
This leads to one of the biggest risks of thrips – some are major vectors for 20 different diseases, many of which are incurable.
Depending on the species, they may attack leaves, fruit, flowers, or other plant parts, and the wounds from their attacks often appear as tiny silvery flecks.
Can Thrips Bite Humans?
This depends largely on the species. Many thrips will land on humans because of bright colors (such as light skin tones or clothing) and attempt to feed, thinking they’re flowers. These bites are tiny cuts, since thrips don’t have the mouthparts for proper biting.
The general result is a mild skin irritation and possibly a brief stinging sensation when the bite occurs. While this is brief and without further symptoms for most people, a few may have sensitivities that result in an allergic reaction to the saliva.
When Are They Most Active?
You will most often encounter thrips in the dead of summer, when the heat and humidity are at their highest. Indoors, they may be more or less active all year due to the steadier indoor climate.
What Does Thrip Poop Look Like?
Thrip droppings are extremely small, but large enough to be noticed. It will appear as tiny black dots, usually amid wrinkles or stippling on leaves and petals.
How to Get Rid of Thrips
Things That WON’T Work
Thrips are highly adaptive, and a lot of methods we normally recommend or talk about simply won’t work on them. So before we get into those things that do work, let’s take a peek at the things that won’t.
Pesticides
Thrips are quick to develop a resistance to pesticides, and while you may find momentary success using them, this is a very brief victory. New pesticides are being developed to combat thrips, and the thrips are building up a resistance almost as quickly.
If you are able to find a pesticide that works (or still wish to try one), be sure to alternate brands and formulas after each application so that the thrips don’t have time to adapt.
Screens
Exclusionary tactics are one of our favorite prevention techniques, but they just won’t work on thrips in some circumstances. For example, window screens have very small holes that most insects can’t get through. However, thrips have body shapes that make it easy for them to slip in through these holes.
Thus, while caulking and similar exclusion methods may help, there’s no real way to keep them from entering an open door or window.
Getting Rid of Thrips From Your Home
It may come as a bit of a surprise, but it’s often easier to get rid of thrips from inside the house than outside.
Thrips are best known for investing houseplants, although they may take up residence in furniture, carpets, or other indoor hiding spots if they happen to land there. Here are a few simple but effective tricks to get them out of your home.
Fly Strips
Do you remember how we mentioned that thrips are attracted to the color yellow? Well it turns out those sticky fly strips you can get just about anywhere work a treat against thrips.
Just hang them near infested plants, and (while it won’t eliminate an infestation) you’ll soon discover many thrips stuck to the yellow translucent strips of death. This can be a great way to reduce the chances of thrips migrating between an infested plant and a nearby uninfested one.
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Neem Oil
We talk a lot about neem oil when it comes to plant pests, and for good reason. This natural extract can kill hundreds of different pests without the risk of creating superbugs. We also love it because neem oil can be applied in one of two ways.
Neem Soil Soaks – 100% cold-pressed neem oil is the purest form of neem. Always make sure you get the cold-pressed variety because neem loses its potency when exposed to heat. You can use pure neem oil to make a neem soil soak – an amazing treatment that can protect plants for up to 22 days.
Create an emulsion by adding a teaspoon of Dawn dish liquid or pure castile soap to either a quart or gallon of water (just a dab’ll do ya!) and gently mix. Now, add 1 tsp of pure neem per quart or 2 tbsp per gallon.
Test a tiny portion of the plant 24 hours before you plan to apply just to make sure the plant isn’t sensitive. Then, pour around the base of the plant, being careful not to get any on the plant itself.
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The roots will soak up the neem, turning it into a systemic insecticide which won’t harm beneficial insects, is safe for use 24 hours before harvesting crops, and will kill any pest that chews or pierces the plant.
Once in the pest, it mimics an insect’s natural hormones, interrupting their development and fertility, and sometimes tricking them into starvation.
While a slow killer, its effectiveness is absolute. Reapply every three weeks as a preventative against all sorts of nasties.
Neem Foliar Spray – Neem oil has at least five insecticidal chemicals, but one in particular is often extracted from neem oil for use in other pesticides. The leftover neem is known as clarified hydrophobic neem oil and may contain .5% to 3% Azardachtin (the extracted chemical).
Get your emulsion and add 1 tsp per quart (or 1tbsp per gallon) of the clarified neem to create a foliar spray.
Use this spray to coat the entire plant, especially the undersides of any leaves. The neem will dissipate in about an hour, suffocating any pests it comes in direct contact with.
Applications outdoors should be done at dusk or dawn, but indoor treatments can be at any time. Reapply the spray every other day for 14 days or until the infestation is gone. You can then reapply every two weeks as a preventative or as a leaf shine (by gently wiping the neem off after spraying).
Steam Cleaning
When it comes to indoor pests, one of the all-around best weapons you can hope to have is a steam vacuum. The hot steam not only kills pests (you may need to move slow or do a couple passes to ensure the heat destroys them), but it can suck out dirt that a normal vacuum misses.
This can be a great tool in making sure no thrips tried to escape into your carpet or couch.
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Getting Rid of Thrips From Your Yard or Garden
Of course, thrips can be a major problem outdoors as well. We’ll just go over a few key spots and the most effective method for each.
The Garden
Neem oil is your greatest ally here, and it will work on most plants (a few are sensitive to neem or soap, however, so be sure to test before using). The only caveat is that you should never use the foliar spray during the day or near beehives, as this can harm beneficial insects.
As for neem products in general, try to avoid using them near fish ponds or other inhabited water features, as the oil is toxic to some aquatic life.
You can also consider planting sacrificial plants. Marigolds repel many pests, but thrips and spider mites love them, so you can use these to draw the thrips away from more valuable plants.
The Swimming Pool
During the summer, your pool is a source of humidity that can attract thrips and other critters. It’s also common for the wind to simply blow thrips at pools where they can land in or beside the pool.
Unlike a lot of insects, thrips are able to wriggle their way to three surface of water and escape drowning, which means you’ll need to use some other method to remove them.
The best method is to shock chlorinate the pool at night. This will kill everything in the pool, but the chlorine needs to dissipate before it’s safe to swim in it. Avoid having too many plants around the pool, as these can give thrips a place to breed.
Overall Defense
Finally, we’d be amiss if we didn’t mention hiring natural predators to protect your entire property. Ladybugs and parasitic wasps both feed on thrips, but you may need to use phytoseiid mites or other tiny predators to reach thrips that are hiding in crevasses. Pirate bugs are also known to feed on thrips.
When choosing a natural predator, be sure to add plants or other things that will encourage them to stick around. They’re available at garden centers and online.
Morgan is a certified entomologist and pest control consultant and a member of the National Pest Management Association.
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