Iris sawfly

The iris sawfly (Rhadinoceraea micans) is an insect pest belonging to the order Hymenoptera and the family Tenthredinidae. The adult is a small, black, shiny wasp-like insect. It is considered a specific pest that primarily attacks iris species, making it a significant concern for ornamental plant growers and gardeners.

The host range is essentially restricted to the genus Iris. Both wild and cultivated varieties, particularly bearded irises, are susceptible to infestation. The pest thrives in environments where host plants are densely grown, providing an ideal habitat for both egg-laying and larval feeding.

The life cycle involves a single generation per year in most climates. The sawfly overwinters as a prepupa in a cocoon within the soil. During spring, pupation occurs, followed by the emergence of adults. Females use their ovipositor to insert eggs into the leaf tissue, ensuring that larvae have immediate access to food upon hatching.

Damage is caused by the larval stage, which feeds on the leaf edges or surfaces. If left unchecked, the larvae can consume the entire leaf lamina, leaving only the main veins. This extensive defoliation weakens the plant, reducing its vigor, decorative value, and potential for successful flowering in subsequent seasons.

• Conduct regular inspections of iris foliage during the spring for early signs of feeding.
• Manually pick and destroy larvae when the infestation is localized.
• Apply insecticides containing pyrethroids or systemic agents during the early larval stage.
• Cultivate the soil around the base of the plants in late autumn to expose overwintering cocoons.
• Remove and dispose of heavily damaged or infested plant material.