Poplar stem sawfly

The poplar stem sawfly (Janus femoratus) is a member of the Hymenoptera order and the Cephidae family. It is a specialist pest that targets various species of poplar (Populus spp.), causing economic and aesthetic damage to both nursery stock and mature forest stands.

The biological cycle of this insect is closely synchronized with the growth of host trees. The adult female uses her ovipositor to insert eggs into young, succulent shoots. Once the larvae emerge, they tunnel into the stem, feeding on the pith and creating internal galleries that disrupt the vascular tissue of the shoot.

This species typically completes one generation per year. Larvae overwinter inside the damaged stems, protected within silken cocoons. Pupation occurs in the spring, followed by the emergence of adults that seek out new terminal shoots to repeat the reproductive cycle during the early growing season.

Damage is characterized by the sudden wilting and drooping of shoot tips, which often turn brown and break off easily at the point of larval infestation. Severe infestations can lead to crown deformation and significant growth retardation, especially in young saplings that are unable to recover from the loss of terminal growth.

Integrated pest management strategies are crucial for mitigation. Key measures include:

• Sanitary pruning and destruction of infested shoots before adult emergence.
• Monitoring adult flight periods to optimize timing for chemical intervention.
• Using systemic insecticides to reach larvae hidden within the plant tissues.