Alder sucker

The alder sucker (Psylla alni) is a small insect classified within the order Hemiptera and the family Psyllidae. It is a specialized pest known to inhabit and derive nutrients from alder trees (Alnus species), acting as a significant phytophagous insect in various temperate forest ecosystems.

This species exclusively targets members of the genus Alnus. Both nymphs and adults colonize the leaves and shoots of host trees. Their presence is often detected by the specific physiological stress they cause to the plant tissues, particularly during the early stages of leaf development in spring.

The life cycle involves an egg stage, followed by five larval instars, and finally the adult stage. The insects typically overwinter as fertilized females or eggs protected within the crevices of the tree bark. As soon as the buds begin to open, the cycle resumes with larvae emerging to feed on the tender foliage.

Damage caused by the alder sucker is characterized by chlorosis, curling, and distortion of the leaves due to the extraction of cell sap. Heavy infestations can lead to premature leaf drop and overall vigor loss, making the trees more susceptible to environmental stressors and other biological threats.

Integrated Pest Management (IPM) is recommended for controlling this insect. Practical strategies include:

• Applying systemic insecticides only when necessary during the early larval stage.
• Implementing good forest hygiene, such as removing debris and dead bark.
• Monitoring populations using sticky traps or branch sampling.
• Encouraging natural predators such as ladybirds and lacewings which are effective biocontrol agents.