6 Common Houseplant Pests—and How to Destroy Them

Houseplants improve the air quality in your home and enhance your home decor. They can also boost your mood and bring hours of enjoyment to your living space. But for all the benefits houseplants bring, they also require some work. Keeping them healthy is a challenge most plant parents undertake without hesitation. However, at some point, you will likely have to deal with houseplant pests. Fortunately, a minor infestation isn't the end of the world. We chatted with Monrovia's plant health and pest expert, Estany Clark, to learn how to identify, treat, and prevent the six most common houseplant pests.

Aphids

Aphids are soft, pear-shaped insects with long antennae that destroy plants by using their piercing mouthparts to feed on the plant's sap. Aphids produce a sugary liquid waste called "honeydew," which causes a fungus called sooty mold to grow on the honeydew deposits, turning leaves and branches black. It's at this point that most aphid infestations are noticed.

Aphids live in colonies on the undersides of leaves. They are under 1/4-inch long when mature, and they are often nearly invisible to the naked eye. Depending on the species, they can be white, black, brown, gray, yellow, light green, or pink.

How to Get Rid of Aphids:

The best way to treat an aphid infestation is to catch it early. "Examine the opening of leaves and flower buds carefully," says Clark. "Many aphids prefer to feed on soft new growth." She also says you can dislodge aphids and eggs from the leaf or bud by squirting them off with a spray bottle or rinsing the plant leaves in the sink. If the infestation is partially bad, follow up with an application of neem oil or insecticidal soap for several weeks to ensure you have killed all eggs.

Spider Mites

These microscopic pests look like tiny, moving dots to the naked eye. Adult females are less than 1/20 inch long! Spider mites live in colonies and will take up residence on the undersurfaces of leaves. Since they are so tiny, most plant parents do not notice them until they see the presence of webbing on their plants. Webbing can be seen between leaves or branches in more severe infestation levels.

Similar to aphids, spider mites cause damage by sucking the sap from leaves. Initially, the damage looks like a stippling of light dots on the leaves. As they feed on, the leaves turn yellowish or reddish and drop off. "Examine undersides of leaves carefully," suggests Clark, "Look for small bits of detritus near the leaf veins," says Clark.

How to Get Rid of Spider Mites:

You can thoroughly wipe or wash the leaves with water in the early stages of infestation on a smooth leaf-plant like ficus, stromanthe, or monstera. "This step should reduce populations quickly," says Clark, "Repeat this process every few days for a few weeks to eliminate any remaining mites." Once that initial mite population is under control, follow up with neem oil to ensure all remaining spider mites are destroyed.

Brown Scale

These inconspicuous little soft-bodied pests resemble flat brown slugs. Like other houseplant pests, brown scale feeds off the plant's sap. They are small and hard to detect, especially if you have a small infestation. However, the pests will look like strange brown bumps on top of or underneath a leaf upon closer inspection.

How to Get Rid of Brown Scale:

Clark says her favorite method of treating scale is wiping or washing leaves and stems to remove the insects and the honeydew they leave behind. This method works well for small infestations. You can even pick or rub them off one by one. You will need to use neem or horticultural oils for larger infestations. And you'll need to keep checking and removing any adults for at least once a month. Clark says that this will ensure any early instars (an insect in the stage in between two successive molts) haven't been missed.

Mealybugs

Mealybugs are soft-bodied insects that appear as white cottony masses on your plant's leaves and stems. "Mealybugs are inconspicuous in their immature stages," warns Clark. "But they are easy to spot in their adult form." Depending on the species, adult mealybugs are an oval shape with a white or gray mealy wax on their surface. "Unfortunately, by the time the adult female is spotted, she's probably already laid and hatched out hundreds of eggs," says Clark. Mealybugs also suck the sap from plants, leaving honeydew on the surface that attracts other pests and encourages the growth of sooty mold.

How to Get Rid of Mealybugs

The best way to treat a mealybug infestation is by spotting it early. Wash or wipe off any cottony mass you see on the leaves or stem. You can also spot-treat an area using a cotton swab and isopropyl alcohol. Dab the alcohol directly onto the mealybugs to kill them instantly. Check your plant every couple of days to make sure you destroy any visible adult.

Fungus Gnats

Fungus gnats are attracted to high humidity and moisture. Most houseplant owners notice the pests when they spot the adults flying around houseplants or gathered at a nearby window. Adult gnats are harmless, but they can become a flying nuisance. Their larvae, however, can cause damage to tender plant roots.

How to Get Rid of Fungus Gnats:

"Fungus gnats are a problem in houseplants where the soil frequently remains wet," says Clark. Getting rid of the gnats requires a change in watering habits. "Only water once the top two inches of soil are dry and infrequently during the cold months," suggests Clark. Also, it's essential to catch the adult gnats so they won't lay new eggs in the soil. A yellow sticky trap is the most effective way to catch them. You may have to use them for several weeks to ensure you get the adult gnats.

Whiteflies

Whiteflies are another sap-sucking insect that is often en masse on the undersides of leaves. They are small, so most houseplant owners don't notice them until they see great clouds of tiny flies take flight when they disturb the plant. Both nymphs and adult flies can cause damage to plants.

How to Get Rid of Whiteflies:

Getting rid of whiteflies starts with suppressing the adult population. Blasting the flies with a strong water stream or using yellow sticky traps helps reduce pest numbers. For heavy infestations, apply insecticidal soap or neem oil. Your plant may need several applications to kill off any remaining whitefly eggs on the plant.

How to Prevent Houseplant Pests

At some point, you will have to deal with houseplant pests. However, you can do a few things to limit a full-blown infestation.

Inspect Often

Prevention is the key to limiting the spread of pests. Inspect leaves and stems every time you water. Thoroughly inspect any plant you purchase as well. The earlier you identify a pest, the easier it is to spot-treat and save your plant.

Isolate New Arrivals

Nurseries grow plants close to each other. Because of their growing environment, it's easy for pests to hop from one plant to another. When you get a new plant, it's a good idea to isolate it from the rest of your collection for a few days to ensure it doesn't have pests.

Quarantine

If you spot any pests on your houseplants, quarantine them immediately. Pests quickly spread from plant to plant. Isolate the plant and treat until there is no sign of an infestation, then you can put it back among your collection.