The rose, a highly valued ornamental plant, attracts a wide range of organisms that feed on its leaves, stems, flowers, and roots. This feeding activity, known as herbivory, can range from minor cosmetic damage to severe defoliation that weakens the entire shrub. Accurately identifying the culprit based on the specific patterns of damage is essential, as the identity of the herbivore determines the appropriate management strategy, whether it requires a systemic insecticide, a physical barrier, or simply a quick rinse with water.
Chewing Insects That Consume Foliage and Flowers
The most visible damage is often caused by insects that chew and consume plant tissue. A common sight in spring is skeletonized foliage, a pattern where the soft green tissue of the leaf is eaten away, leaving behind a network of translucent veins. This damage is frequently the work of sawfly larvae, commonly known as roseslugs, which are the larvae of a non-stinging wasp.
These small, slug-like sawfly larvae feed primarily on the underside of the leaf, creating a thin, papery area that resembles a windowpane before drying out and turning brown. Another culprit for skeletonization is the Japanese beetle (Popillia japonica), which often congregates in large numbers during the summer. Japanese beetles consume the material between the veins of the leaf, leaving a characteristic lace-like appearance.
Caterpillars, the larvae of moths and butterflies, also feed on roses, typically leaving larger, irregular holes or consuming entire sections of foliage. The tobacco budworm, for instance, specifically targets the flower buds and petals, leaving behind black, pellet-like droppings, called frass, near the feeding site.
Other chewing pests, such as the Curled Rose Sawfly, will chew entirely through the leaves, sometimes creating half-moon-shaped cuts along the edges. Distinguishing between these chewing pests is based on the size of the bite and the presence of frass or the insect itself.
Sap-Sucking Pests and Root Feeders
Damage that appears more like a disease or discoloration is often the work of pests that extract fluids rather than chewing tissue. Aphids, for example, are soft-bodied insects that cluster on new growth and tender buds, piercing the plant tissue to suck out the sap. This feeding results in distorted, curled leaves and stunted stems, often coated in a sticky substance known as honeydew.
Thrips are minute, slender insects that damage roses by rasping the surface cells of petals and leaves to feed on the exuded sap. Their feeding commonly causes flower buds to become distorted or fail to open, and petals that do open often show silvery-white streaks or brown edges. Scale insects also feed on sap using piercing-sucking mouthparts on rose canes. Heavy infestations of scale can lead to cane dieback and a lack of plant vigor, appearing as immobile, waxy bumps on the woody stems.
Damage originating beneath the soil line is less obvious but can be severely debilitating. The larval stage of certain beetles, such as the Japanese beetle and the Fuller rose beetle, are C-shaped, white grubs that chew on the fine roots of the rose. This root damage impairs the plant’s ability to absorb water and nutrients, leading to above-ground symptoms that mimic drought stress, such as wilting and poor growth.
Mammalian Herbivores
Larger animals cause the most dramatic and rapid damage, often removing entire sections of the plant overnight. Deer are notorious consumers of roses, attracted to the tender new growth, flower buds, and open blooms. Their feeding is characterized by a ragged or torn appearance to the stems and leaves because deer lack upper incisor teeth and must tear the plant material.
Deer damage typically occurs higher on the plant, often reaching up to six feet or more above the ground, representing their browsing line. Rabbits, conversely, use sharp incisors to make a clean, slanted cut on stems and canes. Rabbit damage is concentrated close to the ground, usually within the first foot of the soil surface, and is severe on young roses or tender spring shoots.
Identifying the Culprit and Practical Management
Accurate identification of the herbivore is necessary before applying any control measures, beginning with a detailed inspection of the plant and surrounding area. Checking the undersides of leaves is crucial for locating small, camouflaged pests like sawfly larvae and spider mites. The presence of sticky honeydew or white, shed skins confirms an infestation of sap-suckers like aphids.
Management should prioritize low-impact and physical methods before resorting to chemical treatments. Small infestations of aphids and sawfly larvae can often be controlled by hand-picking the pests or dislodging them with a strong jet of water. For chewing pests like caterpillars, the biological control Bacillus thuringiensis (Bt) is highly effective and specific, as it only targets the larval stage of moths and butterflies.
Sap-sucking pests are best managed with contact sprays like insecticidal soaps or horticultural oils, which smother the soft-bodied insects. These treatments must be applied thoroughly to contact the pests directly, especially on the undersides of the leaves where many reside.
Protecting roses from deer and rabbits requires physical exclusion, such as fencing or cages, as these animals quickly acclimate to taste or scent-based repellents. A fence must be at least six to eight feet high to deter deer, while a short, secure wire mesh cage can effectively protect young roses from rabbits.