Scale insects are a common problem with houseplants and, unfortunately, really easy to miss because they often look like little shell-like, brownish lumps. Some varieties only grow from 1/16 of an inch to ⅛ of an inch. Sadly, that disguise combined with the bugs' ability to create a protective, hard, waxy film means they're usually able to grow from young nymphs to adults, sucking away at the sap of your plant without being harmed.
There are a few main varieties of this bug. First, the Armored Scale creates a hard shell that protects it from predators (and, unfortunately, pesticides). The Soft Scale variety is the type that makes a waxy film over themselves and is slightly easier to deal with than their hard, armored cousins. Mealybugs are a much larger version of these bugs and are easiest to eradicate. All varieties prefer different plants, which can help you identify which type you are working with.
These pesky insects love warm and dry environments. If you do manage to see them, you will often notice them first on the bottom of your plant's leaves or where the leaves meet the plant's base. Eventually, your plant will show signs of an infestation, looking sickly and withered, with yellowing and curling leaves. If you end up with the Soft Scale variety, they leave behind a ton of honeydew, eventually attracting gross, black fungus. This sooty, moldy residue may be the first sign of these pests you notice.
How to Handle Scales
Luckily, even with how hard they can be to handle, there is hope! You can treat scales the same way you attack mealybugs, as they are a variety of the same insect. Start by pruning and disposing of the infested branches, leaves, and parts of the plant where the bugs reside. From there, you have a few options to consider to try and attack the infestation.
Use regular rubbing alcohol on a cotton swab to dab each pest for mild infestations. You can also attempt to pick and wipe off the bugs if there aren't too many. Luckily, while they aren't super easy to see, they don't often hide too much beyond the surface of your plant.
Another solution is using Arber's Organic Bio Insecticide (pet friendly) as a prevention measure by preparing a spray solution and drenching the leaves and stems according to directions.
For a more substantial infestation, use an insecticidal soap mixed with water to kill the larvae. You'll need to continue with several applications, at least once a week, until all evidence of the bugs is gone. You can use horticultural oils to smother the insect and get rid of bugs at all stages of growth. Some predator insects can also help, like soldier beetles or lady beetles.
If your plant is heavily infested, it may be best to throw it away. You can attempt to use botanical insecticides, however, they can be extremely harsh. Indeed there may be no escaping using synthetic chemical pesticides, so it may be best to just discard the plant to save your other greenery.
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