Iris sawfly

The iris sawfly (Rhadinoceraea ventralis) is a member of the Tenthredinidae family within the order Hymenoptera. It is a specialized pest that exclusively targets various iris species, causing significant aesthetic and physiological damage to plants in residential gardens and professional nurseries.

The biology of Rhadinoceraea ventralis is perfectly synchronized with the host plant's growth. Adult sawflies emerge in the spring, coinciding with the rapid growth of iris foliage. Females deposit eggs directly into the leaf tissue, which acts as a protective nursery and provides immediate nourishment for the hatching larvae.

The larvae, often referred to as false caterpillars, are the primary cause of concern for gardeners. They feed voraciously on the leaves, creating large, irregular holes or eating the foliage down to the veins. A heavy infestation can rapidly defoliate an entire stand of irises, leaving them weak and unable to store enough energy for flowering in the following year.

Managing this pest requires understanding its lifecycle, which includes a pupation stage in the soil. Because the insect spends part of its development cycle underground, integrated pest management (IPM) strategies must focus on both the foliage and the soil environment to effectively reduce local populations.

To control the iris sawfly, consider the following measures:

• Inspect plants frequently in late spring for signs of chewing damage.
• Hand-pick and destroy larvae early in the season to prevent further spread.
• Apply targeted insecticides only if the infestation level threatens plant health.
• Cultivate the soil surface in late autumn to expose pupae to natural predators and weather extremes.