Apricot: San Jose Scales

Problem
The leaves are pale green to yellow, and may drop prematurely from weakened limbs. The bark is encrusted with small (1/10 inch or smaller), hard, circular, slightly raised bumps with dull yellow centers. If the hard cover is scraped off, the insect underneath is found to be yellow or olive. There may be severe limb dieback, and entire branches may be killed. Fruit may be marred by red-purple specks.

Analysis
(Quadraspidiotus perniciosus)

These insects infest the bark, leaves, and fruit of many fruit trees. The scales bear live young in the spring. In late spring to midsummer the young scales, called crawlers, move about and eventually settle on leaves and twigs. The small (1/16 inch), soft-bodied young feed by inserting their mouthparts and sucking sap from the plant. The legs atrophy and a hard, crusty shell develops over the body. An uncontrolled infestation of San Jose scales may kill large branches after 2 or 3 seasons. For further information about scales, see Cottonycushion Scales, Wax Scales.

Solution
During the dormant season, just prior to growth in early spring, spray the trunk and branches with a horticultural oil spray. The crawlers may be killed with an insecticide containing malathion, carbaryl, or diazinon, applied in the late spring.