The sight of a rose bush with stripped, chewed, or holed leaves is disheartening for any gardener. This damage signals the presence of insect pests feeding on the foliage. Identifying the precise culprit is the first step toward protecting the plant and restoring its appearance. The pattern of the remaining leaf tissue offers a distinct clue, helping to differentiate between various types of feeding insects and allowing for a targeted management approach.
Pests That Skeletonize Leaves
One of the most frequent types of damage is skeletonization, where soft green tissue is eaten away, leaving a transparent network of leaf veins. This effect is most often caused by the rose slug, which is the larva of a sawfly, a non-stinging wasp. These small, soft-bodied larvae are typically yellowish-green and translucent, resembling tiny caterpillars as they feed primarily on the underside of the leaves.
Young rose slugs create a distinctive “window-pane” effect in early feeding stages by chewing through the leaf surface but leaving the opposite layer intact. As they mature, these larvae become more voracious, consuming nearly all the soft material and causing complete skeletonization. The damage typically appears in late spring and early summer, though different species of rose slugs can cause damage throughout the growing season. Because the larva feeds on the underside, spotting the pest often requires turning the leaves over.
Pests That Remove Large Sections
When rose leaves exhibit large, ragged holes, notches, or complete removal of sections, the damage is likely caused by larger, chewing insects. The Japanese beetle is a frequent offender, recognized by its metallic green body and copper-colored wing covers. These pests are highly attracted to roses and often congregate in large numbers to feed.
Japanese beetles are known for their destructive feeding habits, often starting at the leaf edges and chewing inward. Their feeding is aggressive, leading to leaves that look severely tattered or lace-like. Adult beetles are active for about six weeks during the summer and will also devour rose flowers and buds, preventing blooms from opening. Certain larger caterpillars, such as rose budworms, can also chew significant holes in leaves and buds.
Recognizing the Leafcutter Bee
A very different and easily identifiable type of damage involves precise, semi-circular or perfectly round cuts along the edge of the rose leaf. This unique pattern is the unmistakable signature of the leafcutter bee, a solitary insect that does not consume the leaf material. The bee uses its mandibles to snip out these clean sections, often from the margins of the leaf.
The bee carries these leaf pieces back to a nesting site, using them to construct protective, thimble-shaped cells for its offspring. Because the bee does not eat the leaf, this damage is purely aesthetic and does not significantly harm the plant’s overall health. Leafcutter bees are valuable native pollinators, so control measures are unnecessary and discouraged. The rose bush can easily tolerate this minor loss of foliage.
Stopping the Damage: Immediate Control Methods
Once the pest is identified, several immediate, environmentally sound steps can be taken to control the damage without resorting to broad chemical treatments. For soft-bodied pests like the rose slug, a simple solution is to dislodge them with a strong jet of water from a garden hose. This physical removal is highly effective because the small larvae cannot easily climb back onto the foliage once knocked to the ground. This method should be done early in the day to allow the leaves to dry and prevent fungal issues.
For larger, more visible pests such as Japanese beetles and caterpillars, the most direct approach is handpicking. Inspecting the plants in the cool morning hours, when the beetles are sluggish, allows for easy removal. The collected pests should be dropped into a container of soapy water, which causes them to drown quickly.
For heavier infestations of soft-bodied pests that water alone cannot manage, an application of insecticidal soap or horticultural oil can be effective. These products work by smothering the insect on contact. Application requires thorough coverage of both the top and underside of the leaves where many pests hide.