If you notice round bumps and a shiny, sticky fluid on the stems and leaves of your houseplant, it probably has scale insects. Scales are tiny pests that often go unnoticed until they multiply in large quantities.  

So, what to do if your houseplant gets scale insects? Don't worry -- this guide gives you a step-by-step procedure for eliminating scale insects on houseplants. 

Things You’ll Need to Get Rid of Scale Insects

Image Credits: Scot Nelson via Flickr

Here’s what you might need to prepare for your battle against scales:

• Spray bottles
• Water 
• Worm castings
• Cotton pads and cotton swabs
• Discarded toothbrush 
• Neem oil 
• Mild dish soap
• Insecticidal soaps 
• Superior horticultural oil

How to Get Rid of Scale Insects on Houseplants

Scale insect's lifecycle starts as an egg, grows to a crawler, and eventually, a full adult. Crawlers are very small, like dust, and move from one part of the plant to another in order to eat. After a few days, they settle down permanently, lose their legs, and begin feeding on the plant sap. Not only do they get a meal, but this is when they develop protective shells.

Generally, when dealing with a scale infestation it's easier to rid of them in their crawling stage. But there are also ways to remove the adult scales from the plant. Here's a step-by-step guide on how to identify, remove, and prevent scale insects on your houseplants. 

Step 1: Check Your Plant Thoroughly

Image Credits: Scot Nelson via Flickr

Firstly, check whether your plant has scale insects or something else. Mealybugs also look like scales and have waxy filaments. Aphids also secrete a large amount of sticky fluid which can lead to black sooty mold. 

There are two common types of scale insects: armored and soft. You can control both these pests using the same methods however, there are some differences in how these scales look.

Soft Scales

To identify soft scale, look for round, oval, like miniature tortoise shells, about 1/8 to 1/4 inch long. The immature scales are soft in color and become darker as they age. Soft scales have hard protective shells and semicircular profiles in the adult stage. Unlike the armored scales, their shells do not lift off their bodies when pried with a sharp knife.

They also secrete honeydew which attracts ants, bees, and flies and gives rise to sooty mold. Other signs of soft scales are yellowing leaves, distorted foliage at the growing tips, twig dieback, and defoliation.

Armored Scales

Armored scales are about 1/6 to 1/8 inch long, circular, and elliptical, but are not bumpy. Unlike their soft counterparts, armored scaled don't produce a sticky sap but, they do carry viruses that can eventually become harmful to your plant.

These pests infest trees and shrubs, causing the leaf cells to die and a yellow or brown halo.

Step 2: Separate and Clean

Image Credits: Pavel Danilyuk via Pexels

The next step you need to take once you identify scale insects on your houseplant is quarantine! Immediately remove your infected plant from your collection and isolate it in a different room. Then, using mild soap and water, clean the area where your plant resided (the table, floor, or windowsill) to avoid any scale insect moving to other plants.

After that, give a quick rinse to your plant under the shower or sink and remove any black mold from the leaves and stems. You can also use lukewarm water on a cotton pad to wipe down the plant. Then, use a toothbrush, cotton swab, or your fingernails to remove the adult scales from your plant by hand. If you observe some parts of the plant are severely infected, pruning is also an option. 

Note: Remember to clean the underside of the leaves, as scale insects often feast there. Check all surfaces of your green friends!

Step 3: Use Worm-Casting Tea

Image Credits: Protopian Pickle Jar via Flickr

Studies show that worm castings (worm excrement) include a natural substance, chitinase, that degrades the protective outer covering of some houseplant pests causing them to die. So, why not prepare a worm-casting tea to remove the stubborn scales from your houseplant. 

Worm castings are ordinary manure you can purchase from your local garden center or order online. You can also prepare worm casting in your garden with vermicomposting.  

To prepare the worm-casting tea, soak 1/2 cup of worm casting in 4 cups of water overnight. Strain this mixture in the morning using a coffee filter or a straining cloth. Next, wipe down your whole plant using this worm-casting tea. Finally, dip a cotton pad in the liquid and remove all the visible scale insects from your houseplant. 

Step 4: Control the Crawlers With Pesticides

Image Credits: Scot Nelson via Flickr

Once you have cleaned your affected houseplant thoroughly with water and worm-casting tea, you need to watch out for further scale infestation on the plant for at least a month. The key is to disrupt the lifecycle of these houseplant pests and ensure that they are no longer spreading. 

Now, you need to prepare your own pesticide sprays to kill the crawlers, and you can do that in two ways. 

• Option 1: Mix 0.5 teaspoons of neem oil with 0.75 teaspoons of mild dish soap and 2 cups of water. 
• Option 2: Mix 1 cup of worm-casting tea with a teaspoon of mind dish soap and 1.5 cups water. 

When using the homemade sprays, ensure that the whole plant is evenly covered with the solution. You may spray some on the soil but never soak the soil with the liquid. Once you finish, just let the plant dry itself. 

Insecticidal soaps or superior horticultural oil sprays will also kill the crawlers. But you need to follow the label directions to avoid damaging the plant. You might also need to clean the area around the plant after spraying oil. 

Follow this process every week for a month. After that, give a final rinse to your plant to remove any soap or oil residue, inspect it thoroughly, and remove it from quarantine! 

Note: Avoid using cold water on your plants. Instead, use lukewarm water to avoid shock.

Step 5: Prevent Scale Insects

Image Credits: Scot Nelson via Flickr

You should follow this precautionary step whether you have scale or have never come across the problem. Inspect your plants regularly for any houseplant pests so that you can catch the problem early. 

Whenever you bring a new plant into the house, ensure you keep it away from other houseplants for at least two weeks. This will help you control issues you may have unknowingly brought home from the nursery. Take the extra care and wipe new plants with water and spray it with worm-casting tea before bringing it inside. The same goes for the plants that you overwinter indoors. 

In general, it is good to spray your plants with worm-casting tea every two weeks to prevent any scale insects from flourishing.

Goodbye Scale Insects! 

One of the best ways to deal with houseplant pests like scales is to use worm-casting tea. Keep an eye on your plants and inspect them every two to three weeks for any possible signs of scale insects. Lastly, follow the measures to prevent scales from entering your house and affecting your precious houseplants. If your plants still get them, you now know what to do. 

Do you have any tried and tested methods to get rid of scale insects from houseplants? Share your tips in the comments below.