Scale Insects
Scale insects are sap-feeding insects named for the scale or shell-like waxy covering that conceals their bodies.
Scale insects can weaken and even kill trees, shrubs and houseplants, but in general, complete loss of the plant is rare.
Description:
Depending on the species, scale insects may be found on plant stems, twigs, trunks, foliage, or fruit. Scale insects thrive in warm, dry environments. The scale bug is small, oval and flat, with a protective tan to brown shell-like covering (scale). Scale generally targets the undersides of leaves and around leaf joints
Most scale insects are small and inconspicuous. The size of scale insects ranges from 1-2mm. Color, shape, texture and other features vary with the species.
Scale insects are generally divided into two categories:
- Soft scales produce a soft, thin, cottony, powdery or waxy layer over themselves that cannot be separated from the insect body. These scale insects often produce copious amounts of honeydew.
- Armored scales have a hard, shield-like cover composed of shed skins and wax that conceals the body but is not attached to the body of the insect.
Scales, both armored and soft, are the most destructive. Armored scales are more difficult to control once mature. Soft scale bugs excrete large amounts of honeydew, which encourages the growth of sooty mold, a black-colored fungus that interferes with photosynthesis. Mealybugs are easier to control. Scales cannot fly so, dispersal depends on the movement of crawlers. Crawlers may be detected by placing double-sticky tape on plant branches.
Scale Insect Control
Scale-damaged plants look withered and sickly. Leaves turn yellow and may drop from the plant. They may also have sticky sap or a black fungus on the leaves and stems. Heavily infested plants produce little new growth. If scale insects are not controlled, death of infested plants is possible. Scale insects are invasive and will infest other plants, so move infested plants away from healthy ones.
Several well-known remedies can be used to eliminate scales from a houseplant. However, there is no easy cure for a scale bug infestation. One possibility is to pick off or gently scrub them loose from the leaves and stems. Dabbing each scale with an alcohol-soaked cotton swab is another possibility for lightly infested plants.
There are also numerous chemical products available for the control of scale bugs. Insecticide sprays, like neem oil, are available at garden centers. Spray applications should be timed to coincide with the crawler stage, which is most susceptible to insecticides. Insecticides must be applied thoroughly each week for a month or more for the greatest results.
For heavy infestations, it is sometimes best to throw away infested plants.
