Rose slugs are the larvae (immature forms) of sawflies, non-stinging members of the wasp family. Three species of sawflies, the rose slug (Endelomyia aethiops), bristly rose slug (Cladius difformis), and curled rose sawfly (Allantus cinctus), are pests of roses. The larvae of some sawfly species are hairy and often mistaken for caterpillars. Others appear wet and shiny, superficially resembling slugs. The larvae generally reach about ½- to ¾-inch in length.

Generally, rose slugs feed at night. Depending on the species, young rose slugs feed on the upper or lower surfaces of leaves between veins, leaving a ‘window’ of translucent tissue that turns brown. As some species of rose slugs get larger, they chew large holes or the entire leaf with only the midrib remaining. Regular inspection of roses is important because feeding typically progresses quickly, and extensive leaf skeletonizing can occur if infestations are not noticed. In addition, with their coloring, they can be very difficult to spot on leaves.

Control: Rose slugs can be controlled by handpicking. They can also be removed by spraying with water. Once dislodged, they cannot climb back onto the plant. Insecticidal soap and horticultural oil are also effective against rose slugs. Other insecticidal sprays that are labeled for homeowner use include acephate, bifenthrin, cyfluthrin, lambda cyhalothrin, permethrin, or spinosad. Sprays should thoroughly cover both upper and lower leaf surfaces. Soil drenches or granular applications of dinotefuran or imidacloprid will control sawfly larvae. Bacillus thuringiensis (Bt) will only control true caterpillars and not the larvae of sawflies. See Table 1 for examples of brands and products.