Rose Slugworms - Leaf damage on Rose Bushes.

The larvae - grub - of the sawfly are yellowish green caterpillars, known as slugworms. They eat into the top surface of the rose leaf, leaving the veins and underside of the leaf looking like a partial skeleton. The damaged leaf eventually dies.

It is the larvae of the sawfly - which in itself does a little damage. However it is the voracious feeding on the leaves of roses by the little grubs that cause the real damage.

The larvae eventually falls to the ground, pupates and overwinters in the soil, ready to emerge as an adult sawfly in early spring.

Bifenthrin is the spray if they are visible - otherwise Provado as a systemic insecticide.

See also - Rose sawfly. Not the same insect.