Cryptomeria scale

Systematic position: The Cryptomeria scale (Aspidiotus cryptomeriae) belongs to the order Hemiptera and the family Diaspididae. It is a significant armored scale pest that primarily impacts various coniferous species, often causing extensive aesthetic and physiological damage in nurseries and urban landscapes.

Host plants: This pest shows a strong preference for members of the Cupressaceae family. It is commonly found on Cryptomeria japonica, as well as various species of juniper, cypress, arborvitae (Thuja), and occasionally yew or pine trees. Its presence can be devastating to evergreen hedge plants and ornamental conifers.

Biology and life cycle: The life cycle involves several stages: eggs laid under a protective scale, mobile crawlers (first-instar nymphs), sedentary nymphs, and adults. Females remain fixed beneath their hardened scale covers throughout their reproductive phase. The crawler stage is the primary period for dispersal, during which the insects can be spread by wind, insects, or human activity.

Damage and economic impact: The Cryptomeria scale feeds by inserting its stylets into the plant tissue and sucking phloem sap. This depletion leads to chlorosis, needle browning, premature needle drop, and stunted growth. In severe cases, the infestation causes branch dieback and reduces the overall vigor of the plant, making it more susceptible to environmental stressors and secondary pathogens.

Protection measures: Management of this pest requires an integrated approach.

• Implementing strict quarantine for new planting stock to prevent introduction.
• Pruning and destroying heavily infested branches to reduce local pest density.
• Applying systemic insecticides during the peak crawler emergence period.
• Utilizing horticultural oils to coat and suffocate the insects under their scales.
• Maintaining healthy soil conditions and water management to support the plant's natural resistance.