Scales, Including Putman Scale and Terrapin Scale
These insects may be common in blueberry plantings, especially if pruning has been neglected for several years and the scales' parasites and predators have been destroyed by insecticide sprays. Scales spend most of their lives as legless, sedentary individuals, usually clustered with other scale insects to form what appears to be a crust--in the case of Putnam scale, Aspidiotus ancylus (Putnam); or shiny brown hemispheres, in the case of terrapin scale, Lecanium nigrofasciatum (Pergande)--on the wood surface. Some scales also reside on leaves and fruit.
Males are produced in late summer; after they mate, the females settle on the wood to overwinter. Live offspring issue forth in the spring to early summer in the form of "crawlers," thereby affecting the spread of these insects. Scales feed by removing sap from the plant, which can reduce vigor, decrease yield, and even cause the decline of the plant. Some scales also produce large quantities of honeydew--a sugary liquid that coats the leaves and fruit and promotes the growth of sooty mold, which can decrease berry quality.
Good scale control is accomplished first by good pruning practices. Removing and destroying old wood during pruning often does much to reduce scale populations. The second approach is the use of dormant oils to smother the overwintering scales. Cover sprays during the growing season usually are ineffective because the scales are protected by their secreted "shell"; however, sprays timed to coincide with crawler emergence can be effective.