Scales (5716)

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 scattered on leaves and stems. Some houseplants have normal brown bumps that are part of the plant. There are two ways you can tell whether brown bumps are scale insects or are a normal part of the plant.

First of all, normal brown bumps may be distributed in a regular pattern. This would be the case, for example, of spore cases on the backs of fern leaves. The normal spore cases are in an orderly array, while scales would be scattered unevenly. They may be up to ¼-inch in size when mature, and vary in color. They produce sugary honeydew, and black sooty mold may be present on leaves below infested branches.

Second, you can scrape scale insects off without damaging the plant. Normal bumps on plants will be harder to scrape off and will usually leave a raw wet spot.

To control scales on houseplants, use insecticidal soap for houseplants or a houseplant spray that is registered for use. Be sure the plant and insect is on the label, and follow all directions carefully. Some houseplants are sensitive to chemical sprays, especially soap.

Scale insects will cling to plants even if they are dead. To tell if they are alive and therefore need control, scrape off a few specimens. If the scale is soft and squishy inside, it is alive. If it is dry and chaffy, the scale insects are dead and no control is needed.

For more information on this subject, Please visit the College of Agricultural Sciences Publications Web site.

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