The largest of the soft scales can stress trees and yellow leaves, if left unattended.
Magnolia scale is the largest soft scale insect, reaching ½ inch in length. It attacks magnolia trees and tulip trees. Star magnolia, saucer magnolia and many hybrids are most commonly and severely affected.
Scale insects can be divided into two groups: armored scales and soft scales. Armored scales secrete a protective cover over their bodies and usually overwinter as eggs beneath the female cover. Soft scales are usually larger and lack the protective cover, but protect themselves with waxy secretions. Soft scale produce honeydew; armored scale do not.
Source: The Morton Arboretum. Photos: Brian Kunkel, University of Delaware, Bugwood.org; John A. Weidhass, Virginia Polytechnic Institute and State University, Bugwood.org