Question:
Small, green worms are eating the foliage on my roses. What should I do?Answer:
The small, green “worms” are probably the larvae of the rose sawfly. Rose sawfly larvae (commonly referred to as roseslugs) have tapered bodies, may be up to ½ inch in length, and are pale green in color. The larvae somewhat resemble slugs, hence the common name of roseslug.
Rose sawfly larvae usually feed on the undersides of the rose leaves. They consume most of the green tissue of the leaf, leaving behind a thin layer of tissue and the veins. The thin layer of tissue that remains eventually turns light brown. Foliage damaged by roseslugs has a window-pane or skeletonized appearance.
Roseslugs weaken affected plants. However, the damage is mainly aesthetic. The damaged plants will continue to grow and should look better latter in the growing season.
Small numbers of roseslugs can be picked off by hand and destroyed. Larger infestations can be controlled with insecticides, such as insecticidal soap, carbaryl (Sevin), or permethrin (Eight).
Learn more about growing roses in this article: Growing Roses in Iowa.