Acacia psyllid

Taxonomic position. The acacia psyllid (Psylla acaciae-decurrentis) belongs to the order Hemiptera and the family Psyllidae. It is a specialized sap-sucking insect that primarily targets members of the Acacia genus, often causing significant stress to both wild and ornamental trees.

Host plants and damage. This pest primarily attacks various acacia species. The damage is characterized by stunted shoot growth, leaf curling, and severe discoloration. Persistent feeding causes the plant to lose its vigor, resulting in chlorosis and reduced growth rates, which can be devastating for young or newly planted specimens.

Biology and life cycle. The life cycle consists of egg, nymph, and adult stages. Psylla acaciae-decurrentis overwinter as eggs or adults in bark crevices. Once temperatures rise, nymphs emerge and settle on young leaf tissues. Throughout the growing season, multiple overlapping generations can occur, leading to a rapid buildup of the pest population.

Economic impact. The injury is twofold: direct sap loss and the secondary growth of sooty mold. Psyllids excrete honeydew, a sugary substance that coats the leaves. This serves as a substrate for black sooty mold fungi, which blocks sunlight and hinders the plant's ability to perform photosynthesis, leading to branch dieback in severe infestations.

Control measures. Effective management involves chemical and cultural practices. Systemic insecticides are most effective when applied during the early stages of nymph development. Cultural control, including thinning the crown to improve airflow and pruning away heavily infested branches, is also critical for long-term health and prevention of outbreaks.

• Regular monitoring of new foliage during spring.
• Application of horticultural oils during the dormant stage.
• Systemic insecticide treatments during active growth.
• Encouraging natural predators such as ladybirds and lacewings.