Scale Insects: Identification and Control

Scales are sucking insects related to mealybugs and aphids, found nationwide. They have a protective waxy, shell-like coating and are stationary for most of their lives (juveniles move briefly). They appear as small brown or black bumps on branches and leaves; some excrete honeydew, attracting ants and fostering sooty mold.

Damage

Infested plants lose vigor, wilt, and have distorted new growth. Branches or whole plants may die.

Control

Light infestations: pick or scrape off scales with a plastic scouring pad. On deciduous plants, spray horticultural oil in winter to suffocate pests. Juvenile scales are best controlled by natural predators or blasted off with strong water jets.

Avoid chemical controls unless the plant is very valuable and all else fails; chemicals kill natural enemies and may worsen scale problems elsewhere. If needed, chemical options for juveniles include acephate, carbaryl, diazinon, malathion.