Scale insects can be divided into two categories: armored scale and soft scale. Behavior and management are different for each group. Both groups live beneath waxy covers that protect them from predators, parasitoids and pesticides. Soft scales secrete a waxy layer over themselves that cannot be separated from their body. They also excrete sugary honeydew and may move from branches to leaves during their life cycle.
In contrast, armored scales live beneath a waxy cover that is not attached to their body. The cover (also called a test) can be removed to reveal the insect hidden below. Armored scales typically do not move once they begin to feed and do not produce honeydew.
The most species-rich family of scale insects is Diaspididae, the armored scales, with more than 2,400 described insects. Armored scales are also some of the toughest nursery pests, because they cause severe plant damage and their “armor” makes them difficult for growers to manage effectively. Their preferred food is many of the trees and shrubs in your nursery. Some of the most common armored scale species in nurseries are euonymus scale, tea scale, Japanese maple scale, false oleander scale and juniper scale. The list will vary based on your region and the crops you grow.