University of Maryland Extension

Scale Insects - Houseplants

scale on houseplant
Fern infested with scale

  • Soft scales are sucking insects that attack a wide variety of plants. Heavy infestations may cause leaf yellowing, stunting, and dieback.
  • Soft scales such as brown soft scale and the hemispherical scale are common pests of houseplants.
  • They appear as raised bumps on leaves and stems, vary in color and can be scraped off.
  • They produce honeydew and sooty mold may be present on leaves below infested branches.
  • Armored scales are not common on houseplants, but may be a problem on some orchids.
  • They are flattened, small and do not produce honeydew.
  • They are difficult to control on orchids, because they may be protected under the sheaths. Careful examination of the plants is essential to control. The scale bodies may be scraped off and treated as for other scale on houseplants.
  • Examine the scale for parasite activity, especially if the plant has been outdoors. Parasitized scales will appear dark in comparison to normal scale insects.

Management

  • Infested plants should be quarantined.
  • Heavily infested plants should be discarded.
  • Wash off or crush any visible scale insects. Often they are found on the stems, underside of leaves, or along the leaf mid-veins. 
  • Treat with an insecticidal soap or horticultural oil labeled for houseplants or a houseplant spray that is registered for use.
  • There are also systemic houseplant insecticides that are labeled to be used in the soil to help control scale.
  • Be sure the plant and insect are on the label and follow all directions carefully. 
  • Some houseplants are sensitive to chemical sprays, especially soap.
  • Multiple treatments are necessary.
  • Outdoors scale is kept under control by beneficial insects. Spray your houseplants with insecticidal soap or oil before bringing them back indoors in the fall. 

close up of scale on houseplant
Philaphedra scale on croton

brown soft scale and honeydew on a leaf
Brown soft scale and honeydew

armored scale on a snake plant
Armored scale on houseplant

close up of armored scale on orchid
Armored scale on orchid

armored scale infestation on  orchid
Close-up of armored scale on orchid

brown soft scale on leaf
Close-up of brown soft scale

close up of hemispherical scale
Hemispherical scale on spider plant

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