Soft scale

Systematic position: Soft scales (genus Lecanium) are members of the order Hemiptera and the family Coccidae. Unlike armored scales, soft scales do not have a separate waxy shield; instead, their own body wall thickens and hardens to form a protective cover, often resulting in a convex or hemispherical shape.

Host plants: These pests are polyphagous, meaning they infest a wide variety of plant species. They are frequently found on deciduous trees such as maples and oaks, various fruit trees like apples and plums, and numerous ornamental shrubs. Heavy infestations can significantly weaken or even kill susceptible host plants over time.

Biology and lifecycle: Most Lecanium species produce one generation per year. They typically overwinter as second-instar nymphs on the bark of twigs and branches. In early spring, these nymphs feed on sap and mature into adults. By mid-summer, females lay eggs underneath their hardened bodies; once these hatch, the tiny, mobile «crawlers» move to the leaves and new growth to establish themselves.

Damage and severity: The primary injury is caused by the direct extraction of phloem sap from the plant, which depletes essential nutrients and stunts growth. Furthermore, soft scales excrete a sticky substance known as honeydew. This provides an ideal growing medium for sooty mold, a dark fungus that covers leaves, reducing their ability to perform photosynthesis.

Control measures: Managing soft scales requires timing applications to coincide with the vulnerable crawler stage.

• Use horticultural oils in the dormant season to suffocate overwintering nymphs.
• Apply systemic or contact insecticides during the crawler emergence period in late summer.
• Prune and destroy heavily infested branches to reduce the overall population.
• Encourage beneficial insects such as lady beetles and parasitic wasps, which are natural predators of scale insects.