Notice the raised, brown growth on my Sago Palm. This is an example of scale.
I'm currently dealing with a really sticky problem — yes, pun intended! — and anybody that has discovered one of their houseplants has a case of scale knows exactly what I'm talking about. While you may think scale is only attacking your plants, think again. Yes, it is first and foremost a plant pest, but this little creature can also wreak havoc on your home.
So what exactly is scale? Scale are parasitic insects which come in over 7,000 different species. They are usually divided into two categories, soft scale and armored scale, and appear like a small growth on plant leaves and stems. They have a waxy body and can range in color from tan and shiny to brown and bark-like, with a hemispherical, oval, or flat shape. Scales survive by adhering to the plant and literally sucking out the sap, eventually weakening and killing the foliage. If left uncontrolled, scale usually results in plant death.
The sticky "honeydew" secretion on my lime tree.
So how do you tell if your plant has scale? Scale can most often be found on the underside of a leaf, or where the leaf of the plant joins the stem. Remember that sticky problem I mentioned? The sticky stuff is called "honeydew," and is a result of the insects sucking the fluids from your plant. If you notice a sticky residue on the surface or floor of where a plant is situated, chances are it has scale. The honeydew can easily ruin hardwood floors, ledges, or any furniture that is nearby. Tha's right — as these little bugs suck the life out of your plants, they also destroy the finish on floors and furnishings. Depending on the surface, honeydew can almost be impossible to remove, short of sanding and refinishing.
Once you know you have scale, how can you get rid of it? First, isolate your infected plant, as scale will transfer from plant to plant. You can try using a soil-applied systemic insecticide for a mild, soft scale infestation. But the most common and effective treatment is removing the scale by hand. Buy a few plain cosmetic sponges, dip them in rubbing alcohol, and gently rub them over the stem and underside of the leaves (it's always wise to test first!). You want to remove all the scales and continue monitoring your plant regularly, removing any new scales you see. Heavily infected or damaged leaves can be removed entirely.
Plants susceptible to scale include (but are not limited to) ficus, citrus, ferns, orchids, and ivies. Keep in mind, plants purchased from mass-growers are more likely to have plant pests than ones bought from small, reputable growers. If you bring a new plant home, it's always wise to quarantine it from your other plants until you can be sure it is healthy.
(Image credits: Kimber Watson)