Of the many different pests that can affect our houseplants, perhaps none are as stealthy as thrips. These tiny insects can fly under the radar for so long that you often have a full-blown infestation before you even notice there’s a problem. What are thrips, and how do you treat for them?
Thrips are very small, flying insects that puncture plant tissue and suck out sap. Their tiny size helps them go unnoticed as they reproduce and continue feeding until the plant begins to show signs of damage. Luckily, there are plenty of treatment options to control for thrips as long as you catch the issue in time.
Thrips can be rather persistent pests, mainly due to their three-part life cycle and how good they are at hiding in crevices of the plant where spray treatments can’t reach them. They can also reproduce quickly, so a small population can blow up to a full infestation within a couple of weeks.
However, with a little knowledge of how these insects operate, you’ll better understand what to expect from them and how you can deploy effective treatment options that will knock back their population, eventually eradicating them from your houseplants for good.
What are Thrips?
Thrips are very small (less than 1/5 of an inch), winged insects that take up residency on several different types of plants. They are most common outdoors, where they tend to go unnoticed. Indoors, however, thrips can do significant damage to the leaves and stems of a houseplant in a matter of just a couple of weeks.
Using their single, large (for their body size) mandible, thrips pierce and puncture plant tissue, where they feed on any sap that flows from the wounds they make. You will likely notice your plant suffering from certain symptoms before you even realize a pest is to blame. Thrips are so small, they are rarely seen on their own, and are often only found when you know to go look for them.
Adults are often winged and darker in color, while juveniles (called nymphs) are cream or pale green and sometimes so small you actually can’t see them without some kind of magnification.
Where Can You Find Thrips on a Plant?
Like aphids, thrips tend to reside anywhere on a plant that gives them access to sap, including leaves, stems, and even flowering parts. Oftentimes, large clusters of thrips can be found on the underside of leaves, mainly due to being more protected than other parts of the plant.
Because nymphs are so small (typically less than 1mm in length), you may not even notice how infested a houseplant actually is. With a bad infestation, you will begin to notice lots of very tiny, white, yellow, or pale green dots scattered across the tops of the leaves of your houseplants. Upon further inspection, you may find these nymphs in larger populations along more protected areas of the plant, usually under leaves, along interior stems, and hidden among flowering parts.
Adults are also elusive creatures that fly, so you might have difficulty identifying them. If you see anything larger than the nymphs or anything winged, assume those are the adult thrips.
Thrips can feed on a wide variety of plants, but in regards to houseplants, they tend to really like palms, Dracaena varieties, and many Aroids, like Monsteras, Alocasias, Dieffenbachias, ZZ Plants, and more).
What Does Thrips Damage Look Like on a Houseplant?
Because these little beasts are so hard to see, it is important to know what thrips damage on your plant might look like so you can keep a sharp eye out for signs of an infestation. As mentioned, thrips are piercing and sucking insects that cause tiny pinprick holes of damage to the plant’s tissue. Overall, it’s pretty low impact, except when the population grows. All that tiny damage adds up to some serious health issues.
One reliable sign of a thrips infestation is if any of your houseplants begin to develop silvery streaks along their leaves or flowering parts. These streaks are actually trails of thrips damage. Along with this, you may also start to see the general appearance of your plant’s leaves begin to look yellow or brown.
Heavily infested plants will show yellow and brown, almost stippled patches in an irregular pattern, and new growth can look stunted, contorted, or deformed. You may also see sooty black spots along leaves or stems. This is thrips fecal matter, which can also be a vector for disease.
If you see this type of damage occurring on your plant but don’t see any obvious pests, investigate further, assuming the plant has thrips. If you have a dark sheet of construction paper, you can hold it under an affected leaf and gently tap the leaf. Oftentimes, you’ll see lots of cream or yellow specks land on the dark paper. These are thrips nymphs.
Upon closer inspection of the plant’s leaves and stem, if you look carefully, you may see these tiny nymphs moving along the leaves. At that point, it’s time to take action.
Life Cycle of Thrips
One of the reasons thrips are so persistent is due to their lifecycle. Because thrips will spend time both on a plant and in the soil, at least some of them will avoid detection and will often rebuild a population after it’s been knocked back by a certain treatment method. Knowing more about how their lifecycle works will aid you in deploying effective treatments against thrips so they don’t come back.
To start, female adult thrips will cut small slits into the leaf and stem tissue of the plant and lay their eggs in these gashes, where they tend to be well-protected. Females can lay eggs all year round. Within a matter of a few days, if temperatures are warm enough, laid eggs will hatch, releasing nymphs.
Nymphs are very small but are voracious eaters. They will feed on the plant sap anywhere from seven to ten days before they drop from the plant down into the soil. Once in the soil, the nymphs pupate quickly and emerge as winged adults, which will fly back up to the plant to start the process over again.
Because of this life cycle, deploying several different treatment methods that treat both the plant and the soil is best. It is also advisable to repeat any treatments every seven days or so to target any new nymphs or adults that have emerged since the last treatment was done.
How Do Houseplants Get Thrips?
Thrips are very common pest outdoors, but the idea of them finding their way into our homes can be a bit unnerving. However, the truth of the matter is that these bugs find our houseplants in a variety of very mundane ways.
Although they are winged insects, thrips are terribly weak fliers, mainly because of their tiny size. However, they are easily carried along by gusts of wind and can easily be blown through an open door or window. If they happen to land on a houseplant once indoors, they happily set up shop.
Alternatively, thrips can be easily carried in outside on our clothes or pets’ coats. In order to minimize this type of spread, be mindful about changing your clothes when you come inside from doing yardwork and before tending to any indoor plants.
One very common way thrips make their way inside our homes is by stowing away on another plant. Any plants that have spent time outside can be harboring several common houseplant pests, like aphids, spider mites, or thrips.
Also, even though plant shops and nurseries try to stay vigilant about pest monitoring, thrips are so tiny that they often make their way through the entire supply chain and into our homes without being detected. Make it a practice to isolate any newly purchased plants for several days to be sure they are pest-free before integrating them into your collection.
Treatment Options to Control for Thrips
Now that you are familiar with what thrips look like, how they reproduce, and how to identify an infestation, you are ready to choose a treatment option that works best for your plant, yourself, and your home.
The good news is that there are plenty of low-impact options to control thrips indoors, and many of these treatments can be used in tandem with others to increase the chances you will eradicate an infestation.
Let’s drill down into what you can do to keep your houseplants thrips-free.
First Steps for Thrips Treatment
Often by the time you realize your houseplant is suffering an infestation of thrips, the population is already large and taking its toll on the plant. In that case, you need a strategy to stop the spread and knock back the population as quickly as possible. Think of these steps as your first line of defense.
First, quarantine your plant. We’ve mentioned that thrips are weak fliers, but they can still spread to other houseplants, so keeping a plant isolated will ensure you don’t have to worry about your entire collection.
Second, a solid spray down with water goes a long way in knocking back an established population of thrips. Water pressure from a sink or hose can dislodge and carry away a good portion of thrips living on your plant and is an easy method for lowering their numbers before deploying any treatments on the plant.
If you have a rather delicate houseplant that may not hold up against a vigorous spray, go ahead and skip this step. It isn’t helpful if it will do more physical damage than good.
Lastly, wherever you isolate your plant, ensure it is properly watered and in a cool, humid environment. Thrips, like spider mites, tend to thrive in drier, warmer conditions, and cooler temperatures will slow their population growth.
Soapy Water Spray
One of the easiest treatments you can use against thrips is soapy water. Soap works to dissolve the insects’ waxy cuticle coating and dries the thrips up over time. A simple mixture of a teaspoon of dish soap with a quart of water in a spray bottle is sufficient to coat thrips and dissolve their protective coating.
In order for this method to work, thrips must come in contact with the soap, so full coverage of the plant must be achieved. This means you need to spray all plant surfaces, including the undersides of leaves and any leaves or stems in the plant’s interior.
You should also plan to repeat a soapy water spray every few days until you no longer see any thrips. This treatment targets adults and nymphs on the plant but might not reach eggs or any pupae in the soil, which is why subsequent treatments are necessary.
Keep an eye on the surface of your plant’s leaves. Repeat treatments of soapy sprays can dissolve the cuticles of the leaves, opening the plant up to more health issues.
Also, try to use natural soap formulas free of additional chemical additives. Some dish soap brands have several ingredients that are unhelpful in controlling thrips and might cause issues with your houseplant.
Yellow or Blue Sticky Cards
Another good way to help control for adult thrips is by installing yellow sticky cards near the plant. Any adult thrips flying near the card can get stuck on the surface, preventing them from laying more eggs.
Blue sticky cards, while not favored among many houseplant pests, tend to attract thrips in droves, so consider using them instead of or along with yellow cards.
Sticky cards are also a great monitoring tool. It might not be a bad idea to keep them near your plant even after you’ve rid it of thrips, just to make sure a population isn’t resurging.
Rubbing Alcohol
Another way to target nymphs and adults on the plant’s surfaces is to deploy rubbing alcohol either as a rub or a spray. Wiping diluted alcohol along the surfaces of the leaves and stems can be an effective means of both physically removing thrips from the plant and dissolving their cuticles, even if they are accidentally left behind.
However, a more effective move would be to dilute rubbing alcohol with water and use it to spray the plant like you would with soapy water. Full coverage of the plant with a rubbing alcohol spray works the same way, and the effects are quick and deadly.
In order to use it safely, dilute Isopropyl Alcohol 70% with water at a ratio of one to twenty. This brings the alcohol content under 4%, which is typically safe to use on plant surfaces. Before you spray a houseplant fully, you may want to test your mixture on a small portion of it to be sure it can handle the spray without any damaging effects.
Again, contact is key, so be sure you are spraying your plant with good coverage in mind and plan on repeating this treatment every few days to catch any newly hatched nymphs or emerging adults.
Insecticidal Soaps
If you want a little more strength in your spray treatment, consider an insecticidal soap to deal with adult thrips and nymphs. These products are usually potassium salts or fatty acids that are mixed with water to create a ready to use spray that dissolves the cuticles on soft-bodied insects, similar to what soapy water or alcohol does. Many formulas are non-toxic and safe to use on most houseplants, but you should always double check the label to make sure.
White Oil (and other Horticultural Oils)
You may have heard of horticultural oils as a way to treat for many different types of insects. Most of these work by mixing some oil-based substance in water to use as a spray that covers and suffocates pests, often including aphids, fungus gnats, thrips, and mites.
They are very effective against adult and juvenile forms of many insects and are pretty low-impact. “White oil” is a term that applies to some horticultural oils made with vegetable-based rather than petroleum-based oils.
Regardless of their origins, most oils are great controls for thrips but plan on applying them several times to fully eradicate an infestation.
Neem Oil
Although many oil-based products do a fine job, my go-to is neem. This natural product does a great job at coating thrips and suffocating them to death. The very cool thing about neem oil is that you can apply it as both a spray and a drench. A ready to use spray is super easy to apply to your houseplant and rarely causes any unwanted side effects.
You can also purchase concentrated neem oil and dilute it enough to apply as a drench, targeting any pupae in the soil and preventing them from turning into new adults. This means that neem oil can effectively treat all parts of a thrips’ life cycle. You can also purchase products like AzaMax, which contain the insecticidal compounds found in neem oil to use as a drench for thrips.
Hydrogen Peroxide Drench
Another control method that targets the short period of a thrips’ life cycle in the soil is a hydrogen peroxide drench. This can be a very useful treatment to prevent any new adults from pupating out of the soil.
One part hydrogen peroxide diluted into four parts of water creates a very easy, DIY drench that fully reacts in the top few inches of soil, where thrips pupae like to hang out. Once you mix your drench, water the plant as you normally would, making sure the entire surface of the soil gets wet.
As the hydrogen peroxide drench seeps down into the soil, it reacts with the organic materials in the soil, including fragile thrips bodies, killing the thrips and producing water and carbon dioxide as the only byproducts.
This method is best when used with another control method since it only targets the pupae in the soil, and there are no lingering effects of the hydrogen peroxide once it fully reacts.
Diatomaceous Earth
Diatomaceous Earth is most often used as a barrier product that, when sprinkled over the surface of a plant’s potting soil, damages any soft-bodied insects that emerge from the dirt. DE is a sandy powder made from the shells of small aquatic organisms called “diatoms.” Although the powder is soft to the touch on our skin, it’s actually very jagged and sharp against small insects, causing irreparable damage to their bodies.
As a powder, DE can help control any new adult thrips emerging from the soil. However, it can also be a very effective spray when diluted in water.
Mix one tablespoon DE with about 500mL of water in a spray bottle. Spray your houseplant like you would with insecticidal soap, diluted alcohol, or soapy water, making sure you get good coverage over infested areas. Your DE spray will coat thrips on the plant and, once it dries, will begin damaging and killing them off.
Chemical Insecticides
If you’ve tried some of the treatments listed above and don’t feel like they pack enough of a punch, you may want to consider alternatives with a little more strength.
Many chemical insecticides are great for controlling thrips, but I recommend finding sprays containing pyrethrins made of plant-derived insecticide compounds. These tend to be as effective as harsher synthetic chemicals and are very low-impact on humans and pets.
Many resources suggest specific systemic insecticide products that work as a long-lasting control for thrips. While this is true, many of the recommended products contain neonicotinoids, a very strong class of insecticides that the plant takes up.
Although effective in treating many insects, plants that contain these compounds can be dangerous to people who come into contact with them or pets who tend to chew on any stray leaves of your houseplants. Be sure to read all labels carefully to know exactly what you are applying in your home.
Don’t Be Afraid to Ditch Your Plant
As you now know, thrips can be very difficult to fully eradicate, especially when populations are dense. If your houseplant has sustained a significant amount of thrips damage or you don’t want to spend the time combating an infestation, don’t be afraid to throw out your plant.
Of course, there are certain plants worth fighting for (looking at you, rare plant collectors!), but if you have something that is easily replaceable and the idea of applying treatments every few days exhausts you, ditch it! You’ll save yourself some time, and more importantly, you’ll remove the risk of spreading thrips to other plants in your home.
Final Thoughts
Thrips are sneaky little plant pests that often take us by surprise. Although they can do significant damage to our houseplants in a matter of weeks, the good news is that we have several different methods to combat them.
Knowing how they feed, reproduce, and spread can help you decide which treatment options work best for you and your plant. Remember to pick controls that target all stages of their life cycle and be consistent with your applications. If you can do that, thrips don’t stand a chance in your home. Good luck!
