Several insects eat rose leaves, and the type of damage you’re seeing tells you exactly which pest is responsible. Skeletonized leaves with only veins remaining usually point to Japanese beetles or rose slugs. Smooth, semicircular cutouts along leaf edges come from leafcutter bees. Irregular holes and ragged edges suggest caterpillars. Each pest requires a different response, and some don’t need treatment at all.
Japanese Beetles
Japanese beetles are one of the most destructive rose pests in North America, feeding on more than 275 plant species with a strong preference for the rose family. Adults are metallic green and copper, about half an inch long, and hard to miss. They chew the soft tissue between leaf veins, leaving behind a lacy skeleton. When leaf veins are tender, they’ll eat the entire leaf. Feeding is heaviest from late June through August, and because beetles release chemical signals that attract more beetles, a few can quickly become dozens.
The most reliable control method is also the simplest: handpicking. Hold a container of soapy water beneath a stem where beetles are feeding, then gently tap the branch. The beetles drop reflexively and drown in the water. This works best in early morning when they’re sluggish. Insecticidal soap and pyrethrin sprays provide temporary knockdown, but they only stay active for a few days and won’t protect new growth. Heavy infestations may need two or three spray applications. The good news is that most rose bushes tolerate moderate defoliation and will push out new growth and rebloom in late summer once beetles are gone.
Rose Slugs (Sawfly Larvae)
Rose slugs look like small, soft caterpillars but are actually the larvae of sawflies, a type of wasp. This distinction matters because caterpillar-specific treatments won’t work on them. If you’ve sprayed Bt (a common organic caterpillar insecticide) and nothing happened, rose slugs are the likely culprit.
Young rose slugs feed on one surface of the leaf, scraping away tissue and leaving a thin, papery “windowpane” that turns brown. As they mature, they chew entirely through the leaf, eventually leaving nothing but the central vein. Damage starts in May and can progress quickly if you’re not checking your plants regularly. Three species are common: one produces a single generation per year, another produces two, and the bristly rose slug keeps reproducing until the first frost, causing damage all season long. All three overwinter as pupae in the soil, with adults emerging in early spring to lay eggs on the undersides of leaves.
Insecticidal soap and spinosad are both effective organic options, but they must contact the larvae directly, so you need to find the slugs on the plant before spraying. Check the undersides of leaves carefully. For prevention, systemic products can be applied to the soil in spring before damage starts. Pull mulch away from the base of the plant and treat the soil directly so the product is absorbed through the roots.
Leafcutter Bees
If you’re finding perfectly smooth, semicircular notches along the edges of your rose leaves, leafcutter bees are responsible. The cuts look almost machine-made, distinctly different from the ragged edges left by chewing insects. Female leafcutter bees snip these pieces to line protective cells where they raise their young.
No treatment is recommended. Leafcutter bees are important pollinators that rarely cause significant harm to healthy plants. Your roses can easily tolerate the cosmetic damage, and spraying would kill a beneficial insect your garden needs. If the notching bothers you visually, the simplest approach is to accept it as a sign your garden’s ecosystem is working.
Caterpillars
Several caterpillar species feed on rose foliage, including corn earworms, eastern tent caterpillars, stinging rose caterpillars, and puss caterpillars. Their damage appears as irregular holes or chunks missing from leaf blades, with ragged edges. Unlike the clean patterns of Japanese beetles or leafcutter bees, caterpillar feeding tends to look messy and random.
Because caterpillars are true moth and butterfly larvae, Bt (Bacillus thuringiensis) works well as an organic treatment. Handpicking is effective for small numbers. Be cautious with stinging rose caterpillars and puss caterpillars, which have urticating hairs that cause painful skin reactions. Wear gloves if you spot hairy or spiny caterpillars on your roses.
How to Apply Insecticidal Soap Effectively
Insecticidal soap is one of the safest and most versatile treatments for soft-bodied rose pests, including rose slugs, aphids, and mites. It works only while wet and must contact the insect directly, which means application technique matters more than with other sprays. Mix a 1 to 2 percent solution (roughly 2.5 to 5 tablespoons per gallon of water) and spray both the top and bottom surfaces of every leaf. Many pests hide on the undersides, so flipping leaves over or angling your sprayer upward is essential.
Timing also affects results. Apply in early morning or late evening, never in full sun or when temperatures exceed 90°F. Heat and direct sunlight can burn treated foliage. The spray kills insects only while it’s still wet, so cooler, slower-drying conditions give it more time to work. You’ll likely need repeat applications every four to seven days until the pests are gone, but avoid excessive treatments since leaf damage can accumulate over time. One more detail: hard water reduces effectiveness. Minerals like calcium and magnesium cause the active ingredients to break down. If you have hard water, use distilled or filtered water in your sprayer.
Protecting Pollinators When Treating Roses
Roses attract bees, so any chemical treatment carries risk to pollinators. Systemic insecticides are especially concerning because once absorbed by the plant, they move into leaves, flowers, pollen, and nectar. Protected inside the plant tissue, they persist at low concentrations far longer than sprays applied to the surface. Research has linked systemic neonicotinoid insecticides detected in pollen and nectar to reproductive harm and reduced survival in honey bees.
If you use a systemic product, never apply it before or during bloom. Wait until petals have dropped. For soil-applied systemics, avoid treating any time before spring flowering. Contact sprays like insecticidal soap are much safer for pollinators because they break down quickly and don’t enter the plant’s vascular system. Spraying in early morning or evening, when bees are less active, further reduces the risk.
Companion Plants That Reduce Pest Problems
Strategic planting around your roses can discourage some of the worst offenders. Scented geraniums, rue, feverfew, parsley, and thyme may help repel Japanese beetles and aphids. Lavender, catmint, sage, marigolds, and oregano are also recommended companions. For a more aggressive strategy, four-o’clocks and larkspur act as trap plants: Japanese beetles are attracted to their foliage, which is poisonous to them. Yarrow pulls double duty by attracting ladybugs, which feed heavily on aphids.
Plant companions at least one foot from your rose bushes to avoid disturbing their root systems. Good pruning practices matter too. Maintaining an open structure with strong air circulation helps prevent both pest infestations and fungal diseases. Remove dead or crossing canes, keep the center of the bush open, and clear fallen leaves from the base of the plant where sawfly pupae overwinter in the soil.