Scale Insect
PestsA group of small sap-feeding insects that attach to bark, leaves, or fruit and often appear as immobile bumps or waxy coatings on plant surfaces.
Scale insects are a diverse group of sap-feeding pests that can affect virtually any tree or shrub species. They are divided into two main groups: armored scales, which produce a hard, waxy covering, and soft scales, which produce a softer waxy or cottony coating. Common species include oystershell scale, pine needle scale, magnolia scale, and cottony maple scale.
What makes scale insects unusual among tree pests is their sedentary adult lifestyle. After a brief mobile crawler stage, most scales settle on a permanent feeding site and develop their protective covering. This immobile habit and waxy armor make them difficult to control with contact insecticides. However, the crawler stage, when tiny nymphs disperse to new feeding sites, represents a vulnerable window for treatment.
Heavy scale infestations cause branch dieback, leaf yellowing, reduced vigor, and can eventually kill branches or entire trees. Soft scales also excrete honeydew, a sugary waste product that supports the growth of sooty mold and attracts ants. Management strategies include horticultural oil applications during dormancy or at crawler emergence, systemic insecticides, and encouraging natural predators like ladybird beetles and parasitic wasps.