Houseplants can be a great addition to any living space, but they can also get infected with some pests. Yellowing leaves and infestation of the leaf tissue with little white dots are symptoms that might mean you have an issue on your hands. Diagnosis is key in getting rid of these critters before it’s too late! Let's talk about what causes them—and how we treat our plants accordingly.
Thrips are tiny, slender insects with fringed wings. They mostly feed on foliage by puncturing and sucking up the contents of their victim’s cell. They leave behind small patches on your plants, easily recognizable net-like patterns that are fairly visible. You can find them, mainly on the stems and undersides of leaves. In their larvae stage, they look like little white sticks, crawling along the plants. And in their adult stage, they can fly. You may notice thrips around spring since they overwinter in soil and emerge when it’s warmer. Their life cycle lasts about one month.
HOW TO TREAT THRIPS - If you suspect your houseplant has these pests then immediately quarantine it until after treatment. My favorite treatment method is Houseplant Systemic Granules by Bonide. Thrips like to lay their eggs inside the tissue of leaves. The Bonide is a sure fire way to eradicate that larvae and the adults. If this systemic isn’t available in your area, look for an insecticidal spray - Captain Jack’s Dead Bug Brew is a great one. And since the spray can’t attack the eggs, you’ll need to spray and treat the plant on a bi-weekly basis until you no longer see anymore thrips.
2. SPIDER MITES
Spider mites are one of the most common houseplant pests. They’re in the arachnid family and relatives to regular spiders. Truly a nightmare! The tiny little pests are hard to see with your naked eye, but you will notice them if they crawl along plant leaves or make webs on the underside of leaves where petiole meets leaf. Their damage will look like yellow stippling.
HOW TO TREAT SPIDER MITES - While I will recommend systemic granules for many common plant pests, it’s important to note that they will not work for mites. In many cases, it may even make things worse. Mites are best treated with an insecticidal soap specially made for mites. You can find them in big box stores or almost anywhere that sells plants. Mite-X is the one I generally reach for. Also, try to work in cleaning your foliage monthly. Reducing the amount of dust that accumulates on your plants really helps keep the problem at bay.
3. SCALE - Scale are small, round insects that thrive in warm, dry environments. Often they’ll be either brown or white and usually look like little round dots along the stems of a plant. Scale are vastly different from other houseplant pests because they’re immobile. Once they latch onto a spot, they stick there. So if you notice bumps along your plant, it's most likely scale.
HOW TO TREAT SCALE - Dip a q-tip in isopropyl alcohol and press it firmly on the scale and they’ll burn right off. You can follow up with the systemic granule or an insecticidal soap.
4. MEALY BUGS
Mealy bugs are a soft-bodied, wingless insect that have a cotton-like appearance. They cause damage by sucking the juice from their host plant. They typically like to go after new growth and will cause yellowing leaves. In masses, the waxy excreations they produce will cause sooty mold fungus to develop.
HOW TO TREAT MEALY BUGS - Since mealies are relatives to scale, I recommend the same treatment as scales. Isopropyl alcohol and the systemic and/or insecticidal spray.
5. FUNGUS GNATS
The most common pest you’ll encounter. Fungus gnats are usually small, black flies flying around the soil. You may even see their slender, black bodies crawling on the top of the soil. The good thing about gnats is that they’re more of a nuisance to us than to our plants.
HOW TO TREAT GNATS - For the short term, yellow sticky traps work by kiling the adult flying gnats. For the larvae, the most effective way I treat for gnats is to mix equal parts of water and hydrogen peroxide and water any affected plant. This will wash any existing gnat and their larvae. You can also water the plants with a spoon of mosquito bits. You can also completely repot the plant, making sure all of the old, infested soil is gone before replacing it with fresh soil. And try to cut back on watering. Gnats are attracted and thrive in moist soil, so letting that soil dry a bit more will drastically reduce population.
Some other things to consider is that stressed plants are more likely to get attacked. So if a plant is being severely neglected it’ll eventually get some sort of pest. Also, make sure to check every new plant you get. New plants are often the culprit of an outbreak. And lastly, know that pests are normal. You can do everything right and still get attacked by spider mites. So take a deep breath and know it’ll be okay because now you know how to treat common houseplant pests.
Thrips vs fungus gnats
The quickest way to tell the difference between thrips and fungus gnats is to understand their behavior. Thrips will always be on the foliage and in their adult form can fly around from plant to plant. Fungus gnats aren't the best at flying and will stay around the soil and bottom of the plant.
You can also get yellow sticky traps. The pest are attracted to them. If you notice long thin bodied pest, then its thrips. Small, round bodied bugs are fungus gnats.
Other plant related blogs:
Bringing plants indoor for fall
Prepping house plants for spring
Hoya as house plants