Black locust moth

Macrosaccus robiniella is an invasive moth species belonging to the order Lepidoptera and the family Gracillariidae. Originally native to North America, this insect has become a significant pest in Europe, where it specifically targets the black locust tree (Robinia pseudoacacia), causing extensive damage to urban and rural forests.

The primary host plant is Robinia pseudoacacia. The moth demonstrates a high level of specialization, preferring the foliage of this specific tree species, which allows it to thrive in diverse environments, from street plantings to large-scale plantations.

The biological cycle of the moth involves several generations per season. Adult females lay eggs on the leaves, and upon hatching, the larvae immediately mine into the leaf tissue. They remain protected within the leaf, feeding on the parenchyma, and eventually pupate within these characteristic mines before emerging as adults.

Symptoms of infestation are easily recognizable by the presence of white, blotch-like mines on the leaves. As the infestation progresses, these mines expand, leading to leaf desiccation, premature browning, and significant defoliation. This process impairs the tree's photosynthesis and overall physiological vitality.

Control strategies for Macrosaccus robiniella focus on integrated pest management (IPM). Key actions include:

• Sanitation: Raking and destroying fallen leaves during autumn to eliminate overwintering pupae.
• Biological control: Encouraging natural predators and using entomopathogenic bacteria where appropriate.
• Chemical treatment: Applying systemic insecticides during peak flight periods, though this is usually reserved for nurseries or high-value ornamental trees.