Rose slug sawfly Endelomyia aethiops
IDENTIFICATION — Smooth, translucent pale-green larvae could attack the leaves of your roses next May and June.
DAMAGE — Feeding on the surface of the foliage between the veins, larvae create a window-pane look. Leaves turn brown and curl. Large infestations may stunt the plant’s growth.
CONTROL — Prune out or handpick small populations. On cloudy days (so you don’t burn the leaves) in early summer, spray all plant surfaces with Safer® insecticidal soap or horticultural oil to smother younger larvae. These controls don’t work as well on older larvae, but most of the damage has already been done by then.
If there are so many larvae that the plants stop growing and blooming, dust the affected plants with an insecticide containing carbaryl, such as Sevin®. Or dilute and spray spinosad on all leaf surfaces in early summer. And all season, pick up debris and leaves from around plants to remove any larvae that may be hiding there.