Scale insects are a common houseplant pest. They are strange insects in that they don’t really look like insects at all. They are basically immobile, remaining in one place for nearly their entire life cycle. They basically sit where they are born and feed off the sap in our plants. They often go unidentified because they don’t move much. They appear as tiny bumps on the stems of plants, and a large enough infestation will eventually kill the host plant.
There are two kinds of scale insects, Armored and Soft Shell. Armored scales develop a hard protective bubble over themselves that measures about 1/8th of an inch long and keeps them firmly in place. Softshell scales secrete a waxy film, which allows them to move a little bit. The females lay eggs inside their shell, and when the nymphs hatch, they crawl a short distance away and begin to make their own shell. Interestingly enough, ants will "farm" and protect scales on outdoor plants because they produce a honeydew that ants love.
How to Get Rid of Scale Insects
There are a few different ways you can get rid of scale insects on your plants, depending on the level of infestation you have.
Symptoms of scale infestation include yellowing or wilting leaves and stunted growth, combined with the telltale bumps on plant stems and leaves. A large infestation will eventually kill a whole plant.
If you’ve caught a scale infestation on your houseplants early, you can treat it a few different ways.
- You can manually pick the bugs off with your fingernails.
- You can dab them with rubbing alcohol or Neem oil on a cotton swab.
- You can prune affected areas off and immediately dispose of infested branches and leaves.
- If you prefer to use non-chemical controls, you can also try using ladybugs or lacewings, though they only prey on the nymphs.
If you have a medium infestation, you can try organic pesticides.
- Insecticidal soap is effective against scale, though you’ll need to reapply several times
- D-limonene is another option that will also need to be applied several times.
- Azamax contains the same active ingredient that Neem oil does. It can be used in a few different ways and its non-toxic for bees and other beneficial insects.
If you’ve got a large infestation, your best bet is to dispose of the affected plant in a sealed garbage bag. If you want to tackle it with an insecticide, it's worth a try—but your plant has probably already sustained enough damage that it will not be able to recover. If you can find a section of the plant that is not infested, take a cutting and start propagating it. Just make sure you treat the cutting with Neem oil or alcohol to make sure there are absolutely no bugs hitching a ride.
Scale infestations can be tough to diagnose, and even tougher to eliminate. The best solution is to prevent an outbreak in the first place. Inspect your houseplants regularly, and make sure you adjust your watering schedule as the seasons change. During the winter, our furnaces dry the air out, so your plants may dry out sooner than expected. Plants that experience water stress, either by over- or under-watering, are more susceptible to pests.
If you need products to help you tackle scale insects, or if you need to replace a beloved plant you lost to scale, stop by the garden center in Greenville. We can offer advice on the best products to deal with them, or help you choose a healthy replacement plant.