Photo courtesy of Marion Kettlewell

Rose slugs

Nuisance

Rose slug feeding damage photo courtesy of Tish Karpa

Rose slugs (Endelomyia aethiops) are an occasional problem of roses. They are a type of sawfly which lays its eggs on rose stems and leaves. The eggs hatch out into these little larvae which do all of the damage. They feed on the underside of the leaf, taking only one layer. This is why you see the white angular patches on the leaves. As that area dries out, it drops out and the leaves look skeletonized with just the veins remaining. Severe defoliation is rare.

Life cycle:

They overwinter as pupae in the soil. Adults emerge in late spring, lay eggs in the leaves, and larvae appear and feed from mid-May through June. The larva are light green with orange heads and are about 13 mm (1/2") when fully grown. There is one generation per year. 

Control:

  • Hand pick the caterpillars, squish and destroy.
  • Spray your leaves including the underside with a strong spray of water.
  • BTK is not effective on rose slugs because they are the larvae of flies and BTK only works on the larvae of moths or butterflies.

Source:

Williams, S.; Skinner, H. (2011). Gardening, naturally: A chemical-free handbook for the Prairies. Regina, Saskatchewan: Coteau Books.