How to Treat Scale on Indoor Houseplants
Despite your best intentions, sometimes nature will take its course and you’ll find yourself treating your plant for scale. These tiny insects can appear as benign brown growths on your plants, but on the underside of their shells, they’ve firmly adhered themselves to your plant and are sucking away at its sap.
Photo credit: Lauren Sottile
Scale varies in color, shape, and size, but most often appears as small, brown, rounded lumps on your plant’s leaves and stems. Two main groups exist: armored or hard scales; and unarmored or soft scales. The names refer to the shell-like coverings which protect the insect body. Control, as with mealybug, is hindered by the protective scale covering the insect. Scales measure up to ⅛ inch long and can be round, oval, or oyster shell-shaped, predominantly brown in color but can range from white to black.
Females may produce hundreds of eggs beneath their shells; eggs later hatch into tiny translucent crawlers about 1/100-inch long. Scale are only mobile in the first moments of their life, until they permanently latch onto the plants foliage. However, these unprotected crawlers migrate to new feeding sites where they become attached to the plant and develop their own protective shells. The existence of only one scale on a plant is rare, as there are more likely additional scale you can't see, so treat your plant at the first signs to prevent it from becoming overrun.
Soft shell scale bugs can be susceptible to insecticide, but the safest bet to begin treating scale regardless of whether it's soft or hard shell variety is to start by removing the pests with your fingernail or a soft toothbrush, or even a Q-tip dipped in rubbing alcohol. With a slight bit of force, most will easily be removed from the plant, but be warned that the stronger adults can be extra resilient. Rinse the plant down under the sink or shower faucet to wash away any errant bugs you may have picked off but dropped onto a different part of the plant. Be careful not to overly wet the soil while doing so.
The next step is to follow this with an insecticide to treat any of the larvae that are leftover. Even if you’ve removed every bug by hand, the larvae is so small it’s almost invisible to the naked eye and may still be present, so it’s important to treat the entire plant with your chosen insecticide. We suggest neem oil for an organic and natural treatment and prevention method, but for serious infestations insecticidal soap may be more powerful. Simply spray the entire plant down from top to bottom (with either mixture), and wipe the foliage clean with paper towels. Please note insecticide should be applied in the evening, or when the plant is removed from the direct sun, as sunlight combined with the insecticide can burn a plant.
A heavy scale infestation. Note the accumulation of scale near the stem, which is the juicier and more nutrient laden part of the leaf.
Separate the affected plant from the rest of your collection while it recovers, taking special care to ensure that none of the plant’s leaves are touching another plant’s. Repeat this treatment every 7 - 10 days and until you no longer see the scale bugs appearing. For future prevention, make sure to inspect all plants thoroughly and regularly. Dusting leaves and inspecting for pests is a great addition to the routine maintenance of plants.