Scale insects are among the few pests succulents occasionally encounter.
When these tiny insects appear, the plant may become damaged and more susceptible to diseases.
Succulents are typically hardy plants, but scale insects are attracted to the sap in the thick leaves.
The word “succulent” comes from the Latin word for sap. These plants have thick, fleshy leaves or stems for retaining water.
Succulent plants are found throughout the world in dry regions, including Australia, South America, and Africa.
While most types of succulents are easy to cultivate on a sunny windowsill, scale insects may threaten the plant.
What Is Scale?
The scale insect classification includes over one thousand different species.
The species vary in appearance.
Most species are round or oval-shaped and light brown or gray, measuring just 1/8-inch to 1/2-inch in size.
The two species of scale insects most likely to attack succulents include soft scale insects and armored scale.
Soft scale insects are easier to treat due to their soft outer shell.
Adult females are often immobile and secrete a waxy substance for defense.
The waxy coating is called honeydew and resembles fish scales, leading to the common name for the insects.
Armored scale insects don’t secrete the same substance.
Instead of a soft outer shell, these insects develop thick outer coatings.
Female soft scale insects lay eggs late in the spring while armored scale insects lay eggs at the start of the summer.
The eggs hatch later in the summer, eventually developing into nymphs.
The nymphs overwinter on the host plant and develop into adults at the start of spring.
The adults then repeat the process.
Scale on succulents is easy to identify. Scale infestations often resemble small bumps.
Depending on the size of the infestation, the bumps may be spread out or clustered together.
What Damages Does Scale Cause?
Scale insects suck the sap from succulent leaves through their piercing mouthparts.
As the pests suck the sap, the succulent may appear partially collapsed or deflated.
The insects drain sustenance from the plant, causing it to weaken.
The plant may appear neglected and in need of water or nutrients.
Weakened succulents become more susceptible to diseases, injury, and infestations from other pests.
If left untreated, the plant may eventually collapse and die.
Another potential threat comes from the honeydew excreted by soft scale females.
The waxy substance attracts other pests, including bees, ants, and various scavenger insects.
The honeydew may also promote fungal growth.
Sooty mold may appear on the plant.
It’s dark, sooty, and foul-smelling.
How To Control and Treat Scale
The protective coatings on scale insects make them difficult to remove with traditional insecticides.
Before trying horticultural oils or homemade insecticides, try removing the insects by hand.
If detected early, removing scale insects by hand isn’t too time-consuming.
Use a fingernail to individually scrape each insect from the succulent.
Along with a fingernail, the insects are typically easy to remove using a credit card or dull knife.
Use caution with a credit card or knife to avoid scraping the succulent.
Severe infestations with dozens or hundreds of insects may require chemical treatment.
Common chemical treatments for scale on succulents include:
NOTE: When treating scale on succulents, keep the infested plant away from other plants.
- Use cotton swabs or Q-tips to apply the rubbing alcohol directly on the insects.
- Most people use alcohol at full strength without diluting it.
- Rubbing alcohol shouldn’t harm the succulent.
- Instead of rubbing the alcohol on the insects, it’s possible to spray them.
- Pour rubbing alcohol in a spray bottle and coat the insects.
- A spray bottle is also needed for applying soapy water or oil.
- To use soapy water, fill the spray bottle, and add several teaspoons of dish soap.
- When using neem oil or commercial horticultural oil, dilute the oil with distilled water.
- Use about one tablespoon of oil for every eight ounces of water.
- Mix the oil and water thoroughly and pour it into a spray bottle.
- Spray oil on the plants at night.
The oil magnifies the intensity of sunlight, increasing the risk of burning the plant.
Chemical treatments are less effective on scale insects but may work with repeated treatments.
To completely remove scale insects, repeat the treatment about once per week until the pests are gone.
- If chemical treatments don’t work, try transplanting the plant.
- The eggs and nymphs may be in the soil and roots of the succulent.
- Remove the plant and spray the roots with soapy water or isopropyl alcohol.
- Allow the plant to dry for several days and then repot with fresh succulent potting mix.
On the rare chance the pests remain, try propagating a portion of the plant appearing healthy and free of scale.