Figure 1. Rose sawfly injury to rose. The rose sawfly is in the upper left corner of the picture. Photo by Amanda Bachmann.
No two gardens are the same, and with that diversity comes a host of interesting pest problems that don’t always occur every year. Recently, a client dropped off a branch from his rose bush (Figure 1). The bottom half of the branch contained crispy leaves that were beyond repair. The top half of the sample still had green leaves, some of which showed feeding injury. There was one insect still present on the sample – a rose sawfly larvae (Figure 2).
Pest Profile & Behavior
Rose sawflies (Endelomyia aethiops (Fabricius)) are also called roseslugs and are in the order Hymenoptera. Despite their common name, they are neither flies nor slugs. The larvae resemble caterpillars. They are small (maximum length of ¾ inch) and light green with a tan head capsule. The larvae feed on the surface of the leaves, and do not chew through the whole leaf. This results in ‘windowpane’ injury or skeletonization of the leaves.
This particular plant also experienced very high temperatures (high 90s – 100° F), which likely made the feeding injury more apparent by drying out the leaves. At this point, there is nothing that can be done to reverse the injury. Continuing to water and fertilize the rose bush will help reduce further stress. The plant can also be pruned back to encourage new growth.
Figure 2. Rose sawfly larvae. Photo by Amanda Bachmann.