What is rose slugworm?
Rose slugworms are the larvae of a sawfly. Sawflies are in the same group of insects as bees, ants and wasps (the Hymenoptera). They have caterpillar like larvae that feed on plants the adults are winged insects that can appear fly-like. Adult rose slugworm have black bodies about 4-5mm long and two pairs of dusky transparent wings, they emerge during mid May to mid June.
Eggs are laid on the foliage and they hatch into larvae that are black with a slug-like appearance. They are pale yellowish-green with light brown heads. Their bodies are translucent and the gut contents can often be seen as a dark green line inside the body. The larvae grow to a length of about 10mm and are somewhat club-shaped with the head end being swollen. When fully fed the larvae go into the soil to pupate.
There are two or sometimes three generations a year between June and October. The second generation in July and August can be the most damaging. Larvae that complete their feeding late in the year overwinter in cocoons in the soil before pupating in April to May of the following year.