Willow club-horned sawfly

Systematic position. The willow club-horned sawfly (lat. Pseudoclavellaria amerinae) belongs to the order Hymenoptera, specifically the family Cimbicidae. It is a significant defoliating insect that undergoes complete metamorphosis during its development.

Host plants. The primary host plant for this species is willow (Salix spp.). These sawflies are most frequently found in nurseries, parkland, and riparian ecosystems where willow trees are abundant. Occasionally, they may be found on poplar trees, but willow remains their preferred food source.

Biology and lifecycle. Adults emerge in the spring to mate and lay eggs within the leaf tissues of host plants. The larvae, which resemble caterpillars, feed voraciously on the foliage as they progress through several growth stages. Once mature, they descend to the ground, where they pupate within a tough cocoon, typically overwintering in the soil or leaf litter.

Damage and economic impact. The damage is caused by the larval stage, which possesses strong mandibles. They consume the leaf blades, often leaving only the main veins behind. Severe infestations lead to widespread defoliation, which causes significant stress to the trees, reduces their aesthetic value, and can stunt annual growth if attacks occur over consecutive years.

• Implement early detection by scouting for egg clusters on leaves.
• Use contact insecticides during the early larval stages for effective control.
• Maintain healthy tree vigor to help them withstand minor defoliation.
• Remove leaf litter and disturb the soil around the base of trees to disrupt pupation.
• Encourage beneficial predatory insects and birds to maintain natural population control.