Rose stem sawfly

The rose stem sawfly, belonging to the genus Cladardis, is a member of the Tenthredinidae family within the order Hymenoptera. This pest is a common but often overlooked threat to rose cultivation, specifically targeting the tender stems of the plants, which leads to stunted growth and loss of flowering potential.

The biology of the rose stem sawfly is centered around its larval stage, which lives endophytically. The female sawfly uses her saw-like ovipositor to slit the epidermis of a young shoot and deposit eggs. Once the larvae emerge, they burrow into the stem, feeding on the pith as they tunnel downward. This internal feeding process causes the shoot to wither and die back.

The development cycle follows the plant's growth rhythm. After completing their development, the larvae exit the stem and drop to the soil, where they form a cocoon and overwinter as a prepupa. In the spring, adult sawflies emerge to begin the cycle anew, with emergence often coinciding with the rapid spring growth of rose bushes.

The impact of this pest is easily identifiable by specific symptoms:

• Wilting, blackening, and curling of the shoot tips.
• Presence of exit holes in the stem where larvae have left.
• Stunted development of new growth and absence of floral buds.
• Weakening of the entire plant structure if the infestation is heavy.

Control strategies require a multi-faceted approach to be successful. Physical removal of infested shoot tips, before the larvae exit into the soil, is the most effective cultural method to break the life cycle. When chemical intervention is necessary, applying systemic insecticides during the early growth stage can protect the interior tissues of the stems from larval damage.