Hackberry nipple gall psyllid

Systematic position: The hackberry nipple gall psyllid (Pachypsylla celtidismamma) is a member of the Hemiptera order and the Psyllidae family. This insect is highly host-specific, primarily targeting trees within the Celtis genus, commonly known as hackberries.

Host plants: The primary host for this pest is the hackberry tree (Celtis occidentalis). It is frequently found in urban environments where hackberries are planted as ornamental street or park trees. While the damage is mostly aesthetic, severe infestations can distress trees already suffering from other environmental stressors.

Biology and life cycle: The lifecycle is synchronized with the bud break of the host tree. Adults overwinter in bark crevices and emerge in early spring to mate. Females deposit eggs on the undersides of young, expanding leaves. As larvae begin to feed, they release secretions that cause the plant to produce a gall, which serves as a protective house and food source for the nymph throughout its development.

Damage and severity: The damage appears as distinctive, nipple-shaped galls on the underside of the leaves, with corresponding depressions on the upper surface. These galls can cover a significant portion of the leaf area. Although the damage is rarely fatal to mature trees, it can cause premature leaf drop and reduce the overall vigor of the plant during the growing season.

Management measures: Controlling this psyllid is challenging once the galls are fully formed, as they shield the larvae. Recommended strategies include:

• Raking and destroying fallen leaves in the autumn to reduce the overwintering population.
• Applying systemic insecticides just as the buds begin to open in early spring.
• Ensuring proper irrigation and soil care to maximize tree health and resilience.
• Preserving local populations of beneficial insects such as lacewings and predatory bugs that feed on psyllid nymphs.