Top 5 Common Houseplant Pests: Identification and Control

Removing scale (a common houseplant pest) from the stem of a Monstera.

Like all plants, houseplants are susceptible to the occasional pest infestation. However, unlike plants you grow outdoors, plants grown inside provide a consistently warm and humid environment for pests which means that a minor invasion can quickly turn into a full-blown infestation if it is not caught early. Knowing how to identify and treat some of the most common houseplant pests will ensure that you are able to prevent infestations and keep your plants in tip-top shape.

While there are many different types of houseplant pests, these five are the most common: mealybugs, common brown scale, aphids, fungus gnats, and whiteflies.

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1. Mealybugs

Mealybugs are small, wingless soft-bodied insects that are a part of the scale family. They are sap-sucking pests that can cause stunted/deformed growth, yellowing leaves, and leaf drop.

These common pests can be identified by the white cottony material that they create to protect themselves. If you have mature mealybugs on your plants you may be able to see them with the naked eye as well.

How to get rid of mealybugs: Use isopropyl rubbing alcohol to spot-treat the plant in any affected areas with a Q-tip or cotton swab. It may take several applications to fully resolve the infestation.

2. Common Brown Scale

While there are over 1,000 species of scale, common brown scale is the most widespread. 

Similar to mealybugs, common brown scale are sap sucking pests that cause deformed and stunted growth. They are usually found on the branches, rather than the leaves of plants. These pests leave behind a sticky, waxy residue which is usually one of the earliest signs of a scale infestation. 

How to get rid of scale: Since scale is difficult to get off of leaves and stems, for severe infestations it is sometimes best to remove the affected branches or leaves entirely. Isopropyl rubbing alcohol can help kill scale and penetrate the waxy coating they leave behind, but applying it can be time-consuming so this tactic is usually only recommended for minor invasions. Insecticide can also help to control a scale infestation.

3. Aphids

Aphids are small, sap-sucking insects that are also commonly referred to as greenflies or blackflies. While they can vary in colour, the most common aphids are usually green or yellow. Because of their size (under ¼ of an inch!) they are incredibly difficult to see with the naked eye.

Aphids are typically found on the leaves of plants, rather than on the branches or in crevices. Since aphids reproduce quickly, it is important to get the infestation under control as soon as you notice it.

How to get rid of aphids: Spray the affected plant vigorously with treatments such as soap and water mixtures, neem oil diluted in water, or vinegar water.

4. Fungus Gnats

Fungus gnats are small, fly-like insects that feed on the delicate roots of plants during the larvae stage. As adults, they are relatively harmless, other than the fact that they are extremely short-lived pests, which means they reproduce quickly. Fungus gnats prefer to lay their eggs in moist or damp soil.

Signs of a fungus gnat infestation include wilting, yellowing leaves, and stunted or deformed growth. You will also see the mature fungus gnats flying around your plants.

How to get rid of fungus gnats: To control fungus gnats it’s important to control their larvae. Using soil drenchers is the best way to control a fungus gnat infestation. Effective solutions include hydrogen peroxide, neem oil mixed with water, and store-bought insecticides. Allowing the soil in your plants to dry out more than usual between waterings may also help to deter egg-laying. Using stick tape in the base of your plants can help to control the adult population around your plants as well.

5. Whiteflies

Whiteflies are small, white flying insects that are extremely common houseplant pests. They lay their eggs on the underside of leaves, where the larvae hatch and feed on the juices of plant leaves and flowers.

Left untreated, whiteflies can cause significant damage to your plants, and will eventually kill them if the infestation is not controlled.

How to get rid of whiteflies: Homemade remedies for treating Whitefly infestations include soap and water solutions and neem oil diluted in water, sprayed on the plant (be sure to focus on the underside of the leaves!). Store-bought insecticidal solutions can also be effective. Like fungus gnats, the adult whitefly population can also be controlled using stick tape.