Scale Insects: Recognizing and Managing

Greedy scale colony.

Scale insects are circular, elongate, or oval insects that often resemble discolored or raised areas on bark, leaves, or fruit. Scales are small and mostly immobile and damage many types of trees and shrubs by sucking out plant juices with their tiny, strawlike mouthparts. Infestations can cause yellowing or premature dropping of leaves, sticky honeydew, and blackish sooty mold. Plant parts can distort or die back, depending on the species and abundance of scales.

Although most plants can tolerate low to moderate numbers of scales, successful management involves correct identification and a combination of factors including proper plant care, conserving natural enemies, controlling ants, and applying low-toxicity insecticides when needed. 

For more information and photos about many common scales in California landscapes, see the newly revised Scales Pest Note by John Kabashima, UCCE Orange and Los Angeles Counties, and Steve Dreistadt, UC Statewide IPM Program.