There are two types of scale insects commonly found on houseplants soft shell and hard shell. Here we will discuss everything you need to know about hard shell scale. For soft Shell Scale check out the ultimate guide here
What are Hard Shell Scale?
Hard shell scale produce a waxy armor around their bodies. It is not directly connected to their soft bodies. Once the waxy shell is formed they are no longer mobile. Females can produce up to 100 eggs or live young, depending on the species. The young crawlers have 24-48 hours to relocate before they must start feeding at which point they will begin to form their own armor.
What do they do?
Scale pierce the leaf or stem and feed on the sap of the plant. Damage shows as yellowing, browning or wilting leaves. Plants growth will be stunted when infestations are big and it can also kill your plant entirely.
Why are they on my plant?
As with most pests, they can appear seemingly out of nowhere. The tiny crawlers can crawl from another plant with scale. They could also blow in through an open window! They can get in via infected potting soil or an unsterilized pot.
How to Identify Scale
They range between less than 1-6mm in size and so can be easy to miss! White to brownish red in color. They appear on plants as a small round raised bump and tend to form clusters on the stems and leaves.
As hard shell scale latch onto the plant, and have a waxy shell to protect them, it can be hard to eradicate them.
One of the best ways to get rid of them is with some rubbing alcohol and a cotton swab, wiping off the scale as you go. You can do this every time you see an insect.
Prune any foliage that has a lot of insects, up to 1/3 of the plant.
Treating with a Neem Oil/Castille soap and water solution in a spray bottle will be effective against crawlers but will not penetrate the waxy shell
Using a systemic insecticide is also a good option but as this will take time to take effect it , you should use it in conjunction with other methods. The plant will absorb the insecticide into the plant tissue which will kill any insect that eats it.
Systemic Pesticides are great for prevention, you apply them directly to the soil and it will kill any scale that attempts to feed on the plant.