Identification
Identifying tree scales requires being able to recognize them at different stages of their life cycle. The life cycle varies across the species but generally includes the egg, larva (crawlers) and adult stages.
The appearance of scale insects can vary widely, from the soft-bodied magnolia scale to the hard-shelled (armored) oystershell scale, which is smaller than soft scales. Armored scales have flat, encrusted shells as compared to the slightly larger, more dome-shaped soft scales.
Crawlers are more mobile and can be observed moving on the surfaces of infested trees and shrubs to feed. It is during this stage that scales are most vulnerable to control measures, before they settle down and develop their protective covering.
Life Cycle
Adult scale insects will present as a covering of small bumps or spots on the twigs and branches of trees and shrubs. These bumps are actually the protective shells of the scale insects, beneath which the pests feed on the plant’s sap.
Most scales reproduce one or two generations per year, with females laying eggs underneath their protective shell. The eggs hatch into larvae, with those crawlers then finding a suitable spot on the plant to feed. After they transition to adulthood and develop their own shells, the cycle continues.
Distribution & Habitat
Tree scale insects are found worldwide, thriving in a variety of environments where their host plants are found. Different types of scales prefer different habitats, but they commonly affect ornamental trees, shrubs and certain fruit trees. The magnolia scale, for instance, prefers the dense, humid regions where magnolia trees are found. Pine needle scales and bark scales are found in drier conditions, with pine needle scales preferring the conifers that grow in those conditions.
Damage & Symptoms
Scale insects drain vital nutrients from their host plants, leading to yellowing leaves, stunted growth and in severe cases, death. As they feed, scales produce a sticky substance called honeydew, which can attract ants and lead to the growth of a black fungus called sooty mold. These infested trees and shrubs become more vulnerable to other pests and diseases, increasing the probability of damage.
Management & Control
Biological Controls: Introducing natural predators or applying horticultural oils during the crawler stage can help control scale populations.
Chemical Controls: In severe cases, chemical controls may be necessary, but they should be used as a last resort to minimize environmental impact.
Prevention
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