5 Common Houseplant Pests and How to Treat Them
It’s the problem you never want to deal with: houseplant pests! But it’s always best to be prepared. This guide will help you recognize and treat common indoor plant pests to keep your plants healthy and thriving. Whether you’ve noticed something sticky, creepy-crawly, or flying around being a general pest in your plants’ space, we’ve got tips to spot pests and treat them right away!
Did you know that underwatering, overwatering, and even letting dust accumulate on your plants can make them more prone to pests? It’s true. Just like keeping a human immune system in good shape means we are less likely to catch a cold, keeping your plants in optimal conditions means they are less likely to catch a pest!
To keep your plants in the best shape possible, be sure to not stress them by underwatering, overwatering, keeping near a draft, shocking them with a change in temperature, or allowing them to build up dust or other particulates on their leaves. Some TLC for your plant babies will go a long way toward keeping them healthy and resistant to pests.
Now let’s get into some of the most common houseplant pests you might come up against.
Spider mites can sneak up on you because they are teeny tiny and hard to spot. But they leave a telltale sign: webs. Just like their namesakes, these mites spin silk-like filaments to create protective webs on the undersides of your plant leaves where they feed. Unfortunately, spider mites can travel from plant to plant by riding a breeze on a piece of their webbing, so if you suspect spider mites you should quarantine the affected plants right away.
Life cycle of spider mites
Spider mites tend to lay eggs that survive the winter on your plants and hatch in the spring. The young mites will pass through one larval stage and three nymph stages before becoming adults and repeating the cycle to reproduce again. The frustrating part is that spider mites can go through these stages and grow from egg to adult in under a week in the right conditions. Female mites can lay up to 300 eggs in just two weeks, which means overlapping generations of spider mites hatching in your plants as each group matures. No thank you!
How to spot spider mites
Aside from the weblike material on leaves, you can also look for feeding spots. Spider mites feed by biting into a leaf and sucking the contents of the plant cells out, leaving pale dots behind and eventually draining a leaf of all its contents resulting in yellowing and leaf loss.
The good news: you can spot spider mites before their webs give them away! When the plant looks to be shrinking and losing size, check the undersides of the leaves to see if you can find evidence of these little beasties feeding off the sap and making your plant fade.
How to treat spider mites
Spider mites quickly adapt to chemical pesticides, so natural and organic options are best for your first line of defense. Start by removing any affected leaves and stems - wherever you see webs, cut that stem off with sterile shears. Throw away discarded plant material in the garbage (not with compost scraps, where the mites will spread). Wash the leaves with insecticidal soap and spray the undersides well to knock off pests. You can also apply neem oil (diluted to package instructions) to the soil and leaves every few days. If you’re able, you can also release beneficial insects such as ladybugs and lacewing to your plant environment -- this is obviously better if you have a small quarantined area so you don’t have ladybugs flying around your living room.
Scale is a common pest that feeds on the sap from your plants. They look like brown ovals, and they can be raised/rounded or very flat. They probably won’t even look like bugs because they barely move! They will look like small scab-like spots on your plant, usually around the joints between stems. Most commonly scale looks brown or tan in color but these pests can also be very light in color. Because the eggs and nymphs are so tiny, it’s hard to spot scale until it may be too late!
Life cycle of scale insects
These little guys take longer to mature than some other pests like mites and gnats, but they’re still annoying to deal with. The whole life cycle takes up to ten weeks. A few weeks for eggs to hatch into crawling nymphs and then another 6-9 weeks for the nymphs to mature into adults who can repeat the cycle. In the nymph stage, scale crawlers navigate to a good place to hang out and eat some plant sap, and then they stay in the same place for most of their lives.
How to spot scale insects
Many pests’ signs look the same, but so does their treatment, so the joke is on them! Scale damage can display as leaf damage (fading yellow or brown, and falling off the plant) on foliage plants or as dents and marks on succulents.
How to treat scale
Scale’s tough exterior helps make it resistant to most chemical pesticides. One of the best solutions is something you probably have in your medicine cabinet already: rubbing alcohol. Soak a cotton swab in rubbing alcohol and run it over the scale insects to remove them from the plant. Check all the joints on your stems and check from multiple angles - think like a scale insect, where would you hide to be alone with your tasty snack? Once you’ve removed most of the insects with the rubbing alcohol swabs, you can treat the plant with insecticidal soap or a solution of 1 teaspoon mild liquid soap (such as plain castile soap) to one quart of water. As with other pests, a neem oil solution and soil soak can help treat scale as well!
Mealybugs are also scale insects but don’t have hard armor like Scale. Mealybugs are white and appear fuzzy with a waxy coating on their bodies. Similar to Scale, they move freely in their nymph stage to find a feeding spot and then don’t move much after that.
Life cycle of mealybugs
Adults lay eggs in a sac-like mass underneath leaves and the female mealybugs will die shortly after laying several hundred eggs in the course of two weeks (anywhere from 300-600 eggs). The nymphs will hatch in 1-3 weeks and travel around the plant to find a suitable feeding place. As adults they don’t move much from their feeding location.
How to spot mealybugs
As mealybugs feed on the sap from your houseplants, they secrete a substance called honeydew which leaves sticky spots on your plant. This is one sign that mealybugs are infesting the plant. Like Scale, you may also see them as flat or rounded white “scabs” on your plant. You might also notice ants in the area; ants consume the honeydew and help protect mealybugs in a symbiotic relationship.
How to treat mealybugs
Back off on any fertilizing you are doing, as mealybugs are attracted to high nitrogen levels in the soil. Start with a cotton swab and good old fashioned rubbing alcohol to remove as many as you can, and then use an insecticidal soap or diluted soap solution to wash and spray down your plant. You can also introduce beneficial bugs like ladybugs, lacewings, and “Mealybug destroyer” mites. Neem oil sprayed on the leaves can also help kill bugs and nymphs and can be left on the leaves as a long-term treatment (reapply every week or so).
Thrips are small insects spanning thousands of species, including varieties with wings and without.Thrips aren’t just a danger to plants; they can also infest furniture, bedding, and even electronics. However, we’ll be focusing on the thrips that infest plants by sucking plant sap from leaves and stems similar to other pests. You need a magnifying glass to clearly see thrips; most are just a millimeter long.
Life cycle of thrips
Thrips reproduce asexually and adult females can lay up to 80 eggs once they emerge in the spring. Eggs hatch into wingless nymphs, which eat plant sap. The nymphs grow through a couple more nymph stages before they drop off the plant to pupate (like a caterpillar turning into a butterfly, only frustrating) and they’ll emerge as adults to repeat the cycle. The timeline on the life cycle depends on the temperature and environment. In warm temperatures, eggs hatch within days, but in colder weather it can take weeks or months to hatch.
How to spot thrips
Thrips hang out in groups to feed, and your approach to your plant will have them jumping or flying away when disturbed. They cut into leaves to form a place to lay eggs, so keep an eye out for small slits in leaves and stalks. Your plant’s leaves may turn pale/silvery and then die off, and your plant (especially plants with blossoms and fruit) may become scarred and twisted due to thrip feeding.
How to treat thrips
The best offense against thrips is a good defense, so keep the soil free of fallen leaves and any debris if your plants are outside. You can attract and trap adult thrips with blue sticky traps. Use running water to knock off any eggs and larvae/nymphs as you can, and introduce beneficial bugs like ladybugs, lacewings, pirate bugs, and predatory mites known as a thrip predator. Neem oil is great for spot treating and spraying leaves and soil.
At first glance, you may think fungus gnats are simple fruit flies that plague the kitchen every summer. However, fungus gnats can cause major damage to your plants because in their larval stage they live in the soil and eat your plant’s delicate roots.
Life cycle of fungus gnats
The life cycle of a fungus gnat is pretty quick; adults live for about a week and lay a few hundred eggs, which hatch in 4-6 days and exist as larvae for two weeks before becoming adults and repeating the cycle. This means you may have all three stages of fungus gnat plaguing your plants at the same time and you’ll need to treat until they are all gone.
How to spot fungus gnats
Fungus gnats look like small mosquitoes with transparent wings, and they’ll probably fly out of your plant’s pot when you water it. The larvae have whitish transparent bodies and shiny black heads (we know, gross).
Sudden wilting and yellowing may indicate fungus gnats, as well as overall poor growth. When the larvae feed on organic matter in the soil, including root hairs, the plant can’t grow as well and will show signs of damage.
How to treat fungus gnats
Allow your soil to dry out and don’t overwater; fungus gnats love a moist environment and will seek out damp soil to lay eggs. You can use a yellow sticky fly or gnat trap to attract the adult gnats, which will fly into the trap and become stuck. You can also treat the soil with a drench treatment to kill eggs and larvae.
For a peroxide drench: Dilute a standard 3% hydrogen peroxide to 20% normal strength (1 part peroxide plus four parts water) and water the plant with this mixture until it runs through the drain holes at the bottom of the pot.
For a Neem Oil drench: Dilute neem oil with water per the package instructions and drench the soil at the roots. You can also spray the neem mixture onto the foliage to deter adult gnats.
Treat ‘Em and Weep
We hope this guide has been helpful in helping you treat your pests! As always, if something isn’t quite right with one of your Wild Interiors houseplants, please send us a photo and description of the issue at firstname.lastname@example.org and we will send it along to our greenhouse team for a diagnosis.