Golden oak scale

Systematic position: The Golden oak scale (Asterodiaspis variolosa) is a member of the Hemiptera order, belonging to the Asterolecaniidae family. It is a specialized sap-sucking insect known for its association with various oak species, which serves as its primary host.

Host plants: The pest primarily infests species within the Quercus genus, such as English oak (Quercus robur) and sessile oak (Quercus petraea). It is frequently found in forests, urban parklands, and nurseries where trees are planted for ornamental or timber purposes.

Biology and life cycle: The adult female is characterized by a circular, convex, yellowish-green or brown shell. The insect completes one generation per year. Winter is spent in the adult female stage, protected by the test (scale cover). In late spring, eggs hatch beneath the scale, and the mobile first-instar nymphs, known as crawlers, emerge to settle on young, tender shoots.

Damage and pest status: As the insects feed on plant sap, they inject toxins that cause the plant tissue to react by forming deep pits in the bark, which is why it is often referred to as a pit-making scale. Severe infestations lead to the deformation of branches, loss of vigor, canopy dieback, and in extreme cases, the mortality of the host tree.

Control measures: Management of the Golden oak scale involves integrated pest management strategies to minimize damage:

• Promoting tree health through proper fertilization and irrigation.
• Pruning and destroying heavily infested branches to reduce population density.
• Timing insecticide applications during the crawler emergence phase in spring.
• Utilizing horticultural oils during the dormant season to smother overwintering adults.