The joy of bringing home a new houseplant is a wonderful experience, but when a pest infestation occurs, that love can quickly turn to despair. If you start to see signs of damage like wilted leaves, spots, or weakened growth on an otherwise happy plant, check for unwanted insects.
Infestations can bring anxiety, but fear not, intrepid plant parents, this article will help you identify and get rid of some common houseplant pests so you can bring back that lovin’ feelin’.
If you notice tiny spots clustered anywhere on your plant, you probably have aphids. Highly detestable and good at hiding, these miniature insects extract the inner sap from stems and leaves, usually around new growth, thus slowly weakening the plant. These prolific reproducers can cause an infestation in days. It would take a long time for them to kill a mature houseplant, but their damage is unsightly—and sticky.
Aphids are soft-bodied, so if weather permits and your plant is strong enough, blast it with the spray of a hose to kill them. Spraying the whole plant with insecticidal soap, neem oil, and/or a homemade mix of mild dish detergent and water will do the trick. A q-tip and rubbing alcohol will kill any insect on contact. Neem oil deters them from coming back, but take all these measures diligently and consistently until you're sure the pests are gone.
2. Spider Mites
Spider mites are members of the arachnid, not insect family, and they're difficult to impossible to see with the naked eye, making them extra pesky! Look for light webbing around leaves and stems if you suspect their presence.
Spider mites weaken plants in the same way aphids do, and they leave another telltale sign—stippling on leaves that eventually turn yellow and brittle.
Mites prefer dry conditions, so a thorough soaking with a hose, or dousing in the sink or shower, and then a spot near a humidifier can probably save your plant. This may not be possible, depending on your plant's water needs, so you can also spray with insecticidal soap, neem oil, or a rubbing alcohol and water mixture.
3. Fungus Gnats
These tiny black flies love damp soil and are extremely (near impossibly) difficult to get rid of. You’ll notice them when you water, as they will fly up frantically anytime the soil is disturbed. Adults either crawl around on top or hover just above soil, and their larvae feed on roots and organic material below. They won’t do extreme damage to a mature plant, however an infestation will take over your plants in no time, and cause major annoyance. They're a bigger problem for seedlings, since they attack roots.
As pesky as they are, you can handle fungus gnats with a few methods. First, water the soil with an insecticidal soap and/or neem oil, and let it completely dry out in every plant in the house (this can be difficult to pull of with multiple plants that have different watering needs, but it helps).
After that, water into a bottom tray for a while, since the larvae live in the top inch of the soil, and remove this top inch or two of soil, discarding it in a sealed container.
Cover the newly exposed soil with sand, if you can. Adult and larval fungus gnats can't live without oxygen, so a top covering of sand will help deter adults from laying eggs, and potentially suffocate larvae. Be careful when using other decorative covers like moss or coco coir, since they seal in moisture.
Finally, yellow sticky traps will catch some adult gnats, but the only way to stop the reproduction cycle is to stop the larvae stage by deploying nematodes (microscopic worms that eat the bug eggs).
Brown scale is often mistaken for a disease, since it’s immobile, has a hard, outer shell, and clings to stems like barnacles on a ship. These tough little critters do move around when they hatch, however, so you want to remove scale as fast as possible before they proliferate and move to other plants.
Insecticidal soap and sprays don’t work on scale as well as they do on aphids or mites, because of how firmly scale attach themselves to plants. You'll have to get a little more physical with these guys.
Get a garbage bag ready to catch the bugs you scrape off with either a dull knife or your fingernail, or try scrubbing with a hard brush if plant stems can take it. Use neem oil, insecticidal soap, or rubbing alcohol to loosen and kill what you can scrub away. If the infestation is especially bad in one area, you may want to prune a part of the plant to help save the whole.
The tiny whitefly is another prolific breeder, so don’t delay when they pop up. Like fungus gnats, whiteflies will fly up when the plant or soil is disturbed. Like aphids and mites, they suck on stems and leaves, and cause discolored, weak growth in affected plants.
Sticky traps can help catch flying adults, and any of the sprays mentioned will kill them on contact. Giving affected plants a good spray with the hose, especially at the underside of leaves where the whiteflies hide and lay their eggs, will also work, since they are soft-bodied. Just don’t let them fly away before you douse them.
Mealybugs are small, white, cottony looking insects that group together, usually at stem joints. They reproduce quickly and are good at hiding, and they will move from one plant to another, although slowly. Quarantine a plant if you see mealybugs on it, or discard it if the infestation has gotten out of hand, since these pests are difficult to eradicate fully.
Unlike fungus gnats, mealybugs will do severe damage to plants in the same way aphids and mites do—by sucking the juices out of stems and joints. Their signature impact is a plant that looks like it’s wilting, even after watering.
Try cutting off infected branches, since these pesky guys tend to gather on one spot. Small infestations can be dealt with by q-tipping rubbing alcohol directly onto the bugs; larger ones by spraying with neem oil, or insecticidal soap.
Miniature but mighty, thrips can cause major damage by feeding on all parts of a plant. They look like tiny seeds or rice, and gather on the tops and underside of foliage. Affected plants will discolor and contort, often developing silvery, splotched leaves.
All the aforementioned sprays will work against thrips, as will sticky traps, since they're winged creatures. They lay their eggs on leaves, but the larvae drop into the soil, so to stop the cycle you have to treat the dirt, too.
Introducing more bugs into your home may seem strange, but consider the benefits of adding predacious insects like ladybugs, lacewings, tachinid flies, and others that specifically dine on pests. There is literally a beetle called the Mealybug Destroyer, and with long unicorn frond sprouting from his forehead, he is a handsome little fellow!
This can be a last resort if you deal with heavy infestation problems, or have a ton of plants. Having these bug-eating bugs around your outside garden can benefit your inside plants as well, since it can reduce the transfer from the outdoors in.
Patience is key when battling infestations. Take preventative measures like quarantining new or infected plants, always seal up potting mix, and de-bug any outdoor plants before bringing them inside. While this is not a comprehensive list, many of the tactics listed above will help you deal with other houseplant pests, should they ever arrive as uninvited guests.