White citrus scale

Systematic position. The white citrus scale (Aulacaspis citri) belongs to the order Hemiptera and the family Diaspididae. This dangerous quarantine pest is widespread across tropical and subtropical regions globally, posing a significant threat to commercial citrus plantations and home orchards alike.

Host crops and damage. The pest primarily targets plants in the Rutaceae family, including lemon, orange, mandarin, and grapefruit. Both females and nymphs feed by extracting sap from the host plant's tissues. This feeding process results in chlorotic spots, cracked bark, deformed shoots, and the eventual dieback of branches, severely compromising the tree's health and overall harvest yields.

Biology and life cycle. The species exhibits pronounced sexual dimorphism. Female shields are circular or pear-shaped and brownish-grey, whereas male shields are elongated, white, and feature three distinct longitudinal ridges. Reproduction is sexual. Under favorable climatic conditions, the pest can complete several generations per year. Mobile "crawler" nymphs disperse across the plant before settling to anchor themselves and begin producing their protective waxy shields.

Economic impact. The high reproductive rate of females allows for rapid infestation. If left unchecked, the population density can cause severe physiological stress leading to tree death. Furthermore, heavy infestations facilitate the growth of sooty mold, which grows on the honeydew-like secretions, further inhibiting photosynthesis and rendering the fruit unmarketable.

Control measures. Management requires an integrated approach combining cultural practices and chemical interventions. Pruning is essential to improve airflow and reduce humidity within the canopy, which creates an unfavorable environment for scale development. When populations reach economic thresholds, horticultural oils and systemic insecticides are utilized. Biological control, specifically the introduction of parasitic wasps from the Aphelinidae family, is also highly effective in suppressing outbreaks.