The pests in your houseplants

  • Follow Gardening

Is your floor or furniture feeling sticky these days? That could be a sign of an insect pest on your houseplants, one that you'd hardly notice otherwise.

That sticky stuff is a sugary "honeydew" secreted by so-called scale insects, who typically start multiplying faster and faster as spring approaches.


Even staring right at your houseplants, you'll have trouble finding the culprits.

Look for nothing more than an occasional shiny, brown bump about an eighth of an inch across. They're especially hard to see on bark, and especially with natural bumps, such as cherry tree bark. (Outdoor plants also may be attacked.)

Flick at a bump with your thumbnail to tell whether it's supposed to be there; scale insects come off easily. Ignore scale long enough and you may soon notice brown bump upon brown bump of scale insects piled up next to each other.

By then, of course, you'll also notice that leaves have wilted or yellowed, perhaps even that the plant has died. Or your feet might stick fast to the floor as you try to walk by.


Let's offer scale insects some sympathy for the drab lives they lead. After hatching from eggs or being born live, the babies crawl around for a few hours or days until they find a place on a plant to settle down.

There, they sink their mouthparts into the plant and start sucking. And that's about it for many female scale insects: A few hours or days of walking around, find a place to eat, then stay put for the rest of your life.

You'd think that the adult males, having wings, might have a bit sparkle in their the lives. Hardly. These males don't even eat. They just fly around and mate — but for only a few hours — then die.


Sympathy aside, that stickiness and those yellowing leaves are reminders that this pest must be controlled.

And control isn't easy because of the protective shield - the scale - these insects grow over their bodies. The protective shield also protects the babies - until they crawl out.

And that's a good time to get them, using various types of sprays. Various plant-extract oils, as well as specially refined petroleum oils, can be effective. Use a dormant oil on leafless plants, a summer oil or superior oil on plants in leaf. Insecticidal soap also works against scale insects.

Hand-to-hand combat is another approach. Use your fingernail to flick scale off, or a cotton swab dipped in alcohol to rub down infested leaves or stems. Dislodging a scale insect breaks its mouthpart so it can never feed again.

Sprays or dislodging need to be repeated every week or two in order to catch young that crawled out from under their protective coverings since the last treatment. You can buy natural parasites and predators to keep continual tabs on scales insects, but they are more effective in greenhouses than home environments.


The second easiest approach for a plant that is thoroughly infested is to just dump it. Different kinds of scale insects - and there are thousands - are somewhat finicky about the kinds of plants they attack, but why risk spreading contagion from a heavily infested plant to your other plants?

And the best way to control scale, with houseplants at least, involves nothing more than moving the plant outdoors in summer. There, some combination of environmental conditions and/or natural predators and parasites often knock back scale insects - until autumn, at least.

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