How to Control Houseplant Pests without Losing Your Mind

Houseplants seem like a great idea. That is until you have them for awhile and suddenly they are covered in Bugs! Webs! Sticky goo! If you’re ready to ditch your houseplants for plastic bug-less versions, read this before you start shopping the silk plant aisle.

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Houseplants are trendy again.

At least that’s what I read in a magazine recently. They’ve always been trendy at my house.

But maybe the idea of houseplants is new at your house. There are so many Zen-inducing scenes floating around social media, who wouldn’t want a few plants to add a relaxed vibe to their home?

If you’ve recently added plants to your home for the first time, I’ll bet it was all Instagram-worthy and relaxed for awhile. You wondered why you didn’t get more plants when you bought the ones you did. Maybe you even went out and actually bought more plants.

But then one random day you noticed little bits of cotton all over your plant. Or webs. Or weird looking bumps. Maybe you had little flying insects buzzing around every time you brushed by the plant. Maybe your plant was full of some icky sticky goo.

Now what?

Unfortunately, most of the time our homes are relatively cool and low in humidity and light– particularly during the winter months. Most houseplants prefer bright, warm and humid climates like their native lands. Living in a less than ideal environment is a significant stress on a plant; a stressed plant tends to be weaker and more susceptible to pests.

Sometimes we set ourselves up for houseplant pest problems. Too much fertilizer applied in the winter months encourages growth when conditions are not ideal, producing spindly, soft succulent growth that pests love.

I used to never fertilize my houseplants at all during the winter months when plants aren’t really growing and conditions indoors are inadequate. A couple of years ago I experimented and used a weak fertilizer solution a couple of times (1/4 the strength listed on the label or less) over the winter and was pleased with the results.

As a rule of thumb, I don’t increase how much fertilizer my plants get until I put them outside for the summer. (More on why your plants need summer vacation below).

Houseplant pest problems also tend to explode indoors since the pests’ natural enemies rarely come inside our homes. Most of us would prefer to keep it this way– I don’t know about you, but I don’t really want natural pest predators like ladybugs or praying mantis flying around.

Keep an eye out for the “top five” most hated houseplant pests:

Mealybugs are soft-bodied insects that look like bits of white cotton. Usually, they go unnoticed until they are adults because that’s when they produce their white cottony covering. They are also extremely good at hiding, so look for them under leaves and in any and all cracks and crevices on your plants. In the case of orchids, they even show up on roots! They are sucking insects, piercing the stems and leaves to ingest the nutrient-rich sap. Mealybugs produce honeydew, which often makes affected plants sticky.

Honeydew is what the mealybugs excrete after ingesting the plant sap.  It’s high in sugar and tends to attract a black powdery fungus called sooty mold which feeds on these sugars. Heavy infestations of mealybugs can distort new growth in plants. Control small infestations by handpicking or dabbing with a cotton swab dipped in rubbing alcohol.

Aphids are another sucking insect that produces honeydew. They are small soft-bodied insects, ranging in color from nearly colorless, to green, to yellow to almost black. Most of the time they can be controlled by washing or wiping them off affected plants. In extreme cases, they distort new growth.

Scale insects come in many shapes and sizes, but the most common ones indoors range in color from yellow to nearly black and resemble small droplets stuck to stems and the undersides of leaves. It’s easy to overlook scale, especially on houseplants that have woody stems like Ficus and potted citrus trees. They have a hard protective shell that prevents them from being easily washed off or affected by insecticides. Remove small numbers by hand, but this may be impossible for large infestations.

Spider mites are extremely common indoor pests, in part because they thrive in dry climates, and most homes are very dry in the winter. Treating them early on is best, but they can be hard to diagnose. Early infestations look like faint yellow dots across leaves, with mites generally on the undersides of leaves. The faint yellow dots look like someone sprinkled salt across the leaf. Once you’ve seen it the image will be seared into your brain!

They are very tiny but if you shake your plant over white paper you will see them crawling on the paper. Advanced infestations reveal how they got their name, as the mites engulf plants in material resembling fine spider webs. Increasing the relative humidity indoors is a good way to prevent spider mites. I have never had success with increasing humidity to treat an infestation.

Fungus gnats are very common pests whose larvae thrive in wet potting mix with high organic content. The adults are just annoying tiny flying insects, but larvae live in the soil and eat the roots of plants; in large numbers, they can seriously harm plants. The best control measure is to let the mix dry between watering. Other options include spraying to kill the adults or using specific nematodes or beneficial bacteria (Bt) in the potting mix to kill the larvae.

One “last chance” option for treating fungus gnats is to change the potting mix completely, but proceed with caution as this can damage a plant’s delicate roots. Keep in mind that the source of the fungus gnat eggs could be the potting mix you used in the first place; if you try this option, buy a fresh, dry bag. If the potting mix has gotten wet either at the store or your house, it can harbor fungus gnat eggs.

Houseplant Pest Treatment Options

There are many different treatments available for houseplant pests. As with our outdoor gardens, you must learn to read labels when treating indoor pests. Using pesticides indoors is especially a safety issue where children and pets are concerned. For me, I prefer to either handpick the pests off the plant or use an insecticidal soap that is safe for use around children and pets.

• Before applying any treatment, remember pests can move from plant to plant. At the first sign of a problem, I isolate the affected plant away from the rest, usually in a different room.
• If you use pesticides, remember one spray, drench or granule will not always control all pests. Plus, some pesticides, even if they are labelled for indoor plants, can be very toxic. Proceed with extreme caution.
• Growing edible crops indoors is increasing in popularity. If you are growing edibles, you absolutely must read labels and then read them again. Just because a pesticide label says it’s safe for use on an edible crop does not mean you can use it indoors.
• Remember also that just about every sort of treatment out there will need to be repeated at some point. While a given treatment will often kill adults in one treatment, they typically have no effect on eggs; these eggs will hatch, and the pest is back in business. Read the label of your pesticide to find the product’s suggested application interval.

Plants Need Summer Vacation too!

I encourage you to move your houseplants outdoors this summer. This exposes any pests on the plants to natural enemies, and if any of your indoor spaces are harboring pest eggs, they have no plant material to feed on when they hatch, breaking the cycle. While you’re at it, thoroughly wash down and sanitize where your plants live indoors after you move them outside.

An Ounce of Prevention Really Does Help

With all of these pests, periodically inspecting your plants throughout the year, not just in the winter, will go a long way in minimizing pest problems. Also, don’t be afraid to thoroughly inspect any plant before you purchase it. I have created my own trouble by failing to do both.

I love resuscitating plants from the clearance table. Years ago, in my excitement over a great “deal” on a plant, I didn’t look all that closely at it. Unfortunately, mealybugs had infested that plant.  And I brought that plant into my apartment. The mealybugs spread and eventually wiped out my African Violets, and most of my orchids. Some deal.

I compounded the problem by not inspecting my plants regularly. Mealybugs, like a lot of pests, like to hide under leaves or in flowers, out of sight. I discovered too late in the game that some mealybugs love to feast on orchid plant roots rather than leaves.

Keep the Greater Good in Mind

If a pest has severely infested your plant, it may be best to discard the plant. In the long run, you may avoid having the pest spread among the rest of your plants. During the Great Mealybug Infestation, I shuddered at the thought of giving up on a plant and throwing it out.

I tried multiple treatments which didn’t work, and in the meantime, the mealybugs spread to nearly all my plants. Had I thrown out the first few heavily infested plants I’d found before trying to treat everything, I might not have lost as many plants, especially my beloved orchids. In hindsight, just the orchids alone were worth a lot more than my bargain plant that spread the pests in the first place!

When you get your pest problems under control, why not try your hand at propagating African violets, or making a macramé plant hanger?

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