Roses are a favorite landscape plant of many homeowners. Their beautiful blooms are classic show-stoppers. With so many long-blooming, low-maintenance roses on the market these days, you would think there would be no need for an article discussing common pests of roses. But unfortunately, while there are plenty of rose varieties that are resistant to common rose diseases, such as black spot and powdery mildew, there’s no such thing as a rose that’s completely resistant to insect pests. Even low-maintenance rose varieties face pest issues. I’d like to introduce you to eight critters who make holes in rose leaves, distort foliage, and destroy flower buds. I’ll also share some tips for managing them safely.
Why use organic rose pest solutions
Before introducing the pests themselves, it’s important to understand why the kind of pest control you use is critical to your garden’s overall health. Yes, rose pests are a common complaint of rose-loving gardeners, but with pollinator populations on the decline, it’s important for us to choose organic rose pest solutions, rather than synthetic chemicals that could harm other wildlife.
Many popular rose pest control products are granular systemic pesticides that are sprinkled on the soil around the base of the plant. They are then absorbed through the plant’s roots and travel up into the foliage. These products include active ingredients that move through the vascular tissue of your rose plant, killing whatever nibbles the leaves. This might seem like a good thing at first because systemic products are easy to use and long-lasting. Eventually, however, systemic pesticides make their way into the pollen and nectar of the plant, where they bring harm to the pollinating insects visiting the blooms.
Neonictinoids, roses, and pollinators
The most common systemic pesticide ingredient used in rose pest controls in the United States is the neonictinoid imidacloprid. Neonictinoids have made news recently for their negative impact on pollinators and other non-target insects. Avoid systemic pesticides at all costs when controlling pests on roses and other landscape plants. These products also end up in the food chain when birds, frogs, toads, and other creatures eat the insects that have ingested the pesticide. They also harm soil life and will likely harm birds, pets, and any mammals who eat the granules.
Truth be told, there’s no need for any of these toxic pesticides anyway. As you’re about to learn, there are many organic rose pest controls that are effective and safe to use, and will not bring harm to non-target wildlife.
8 Common rose pests and how to control them
1. Aphids: Sap-sucking rose pests
There are hundreds of different species of aphids in North America. They’re found from coast to coast in nearly every climate, and on most other continents as well. Aphids are tiny, pear-shaped, soft-bodied insects measuring up to 1/8″ long. They can be green, yellow, brown, red, gray, or black. Some species have winged forms; others do not. At the hind end of each aphid are two small, tube-like structures called cornicles.
There are many different plants that host aphids. Roses are among the most susceptible. Aphids damage roses by feeding on the leaves, stems, and buds. These rose pests use a needle-like mouthpart to penetrate plant tissue and suck out sap. They feed in groups on new plant growth or on leaf undersides, and cause stem tips, new leaves, and buds to be curled and distorted.
At my house, I completely ignore aphids on all of my plants. Within a week or two of noticing them, the beneficial insects always find the aphids and bring them under natural control before they cause significant damage to my roses and other plants. If the infestation is severe and no beneficials show up, remove aphids with a sharp stream of water from the hose. This knocks them off the rose plants and onto the ground where they’ll quickly be found by ground-dwelling predatory insects, like spiders, ground beetles, and others. Hand-squishing is also effective. But, as I said, most of the time, predatory beneficial insects naturally bring aphid populations under control.
Product control is seldom necessary for these rose pests, especially if you interplant your roses with sweet alyssum, which lures or shelters in many of the beneficial insects that eat aphids. But, if your rose aphid infestation is severe, horticultural oils or insecticidal soaps work well.
2. Rose sawflies (rose slugs): Rose pests that skeletonize leaves
If you come out to your garden and find your roses with holes in their leaves or completely skeletonized leaves, check the plants for rose sawflies. Rose sawflies are tiny green caterpillar-like larvae that measure a mere 1/8″ to 3/4″. They have light brown heads. Also called rose slugs, they are not true caterpillars or slugs, but rather the larvae of a type of fly.
You’re most likely to find rose sawflies on the undersides of leaves. They’re very small when they first hatch, so they can be tough to spot. Look carefully on the undersides of the leaves. If sawflies are the rose pests to blame, hand-squishing works, but it takes a lot of time. Again, inter-planting roses with flowers like sweet alyssum, dill, fennel, wallflowers, and cosmos, attracts parasitic wasps, tachinid flies, and other beneficials that control them naturally.
If your roses are being decimated by this pest, product controls with the active ingredient spinosad are very effective (such as Monterey Insect Control and Captain Jack’s). Though they are safe to use even on certified organic farms, spinosad-based products may harm pollinators if misused. Spinosad is a fermented bacterial product that is labeled for use on many common leaf-chewing garden pests. For spinosad to work against sawfly larvae on roses, the tops and bottoms of all leaves must be covered.
3. Thrips: Bud-destroying pests of roses
Rose thrips (Western flower thrips, in particular) are tiny (1/20″), slender, brown to yellow insects that cause flower buds to become distorted or streaked with brown. They feed by sucking out cells. When feeding on leaves, they leave behind silver streaking. Gardeners are likely to find dark specks of excrement on thrips-infested rose plants. It’s so sad when rose thrips strike, not only because they destroy your blooms, but also because they’re quite difficult to control.
Thrips tend to be worse in landscapes where roses are planted in large swaths. Since thrips feed inside rose buds as well as on the leaves, controlling them is very challenging. To confirm an infestation, shake your rose buds and leaves over a sheet of white paper and look for the insects. If you suspect they’re hiding out inside the buds, cut a distorted bud apart and look inside for the tiny insects.
To control thrips on roses, encourage thrips-eating beneficials, like green lacewings and minute pirate bugs, by planting a diversity of plants around your roses. In severe cases, consider purchasing minute pirate bugs from an insectary and releasing them onto your rose plants. Prune and destroy any damaged buds. If damage is severe, spinosad-based organic insecticides, as well as neem oil-based products, are effective, though they offer limited control on any rose thrips found inside the buds.
4. Slugs: Slimy pests that chew holes in rose leaves
Slugs chew ragged-edged, random holes in rose leaves. Their damage is most severe during wet growing seasons. These mollusks are rose pests that excrete a slimy coating on which they travel. If you see slime trails, along with holes in the margins or center of rose leaves, slugs could be the problem. To confirm, head out to the garden at night with a flashlight and inspect the rose bushes. Slugs typically “work their magic” at night.
To control slugs on roses, encourage birds, snakes, salamanders, toads, frogs, and ground beetles to make a home in your garden. Water in the morning so rose foliage dries by nightfall.
Copper strips can be wound around the base of rose canes to deliver a mild shock to slugs who touch it. Slug baits containing iron phosphate are extremely effective and much safer to use around kids and pets than baits containing the synthetic chemicals metaldehyde or methiocarb. If you’re looking for more ways to manage these slimy rose pests, check out this article detailing 8 organic slug controls.
5. Japanese beetles: Day-feeding rose destroyers
While Japanese beetle grubs feed on the roots of your lawn, the adult beetles use over 300 different plants as dinner, including roses. These rose pests are most problematic east of the Mississippi, though areas to the west face Japanese beetle issues, too. Unfortunately, their range is spreading. They feed during the day and are unmistakable.
Japanese beetle adults are copper-colored with a green head. They raise their rear legs when disturbed in a defensive posture. As they feed on roses, these beetles release a pheromone that attracts more beetles, so early and steady control is a must.
Handpick adult beetles and drop them into a jar of soapy water. Better yet, cover your rose plants with a layer of floating row cover or tulle for a week or two after you spot the first beetle of the season (typically in mid-summer). Japanese beetles are active for only 4 or 5 weeks each season, so temporarily covering the plants prevents the most damage.
The best organic spray product for adult Japanese beetles on roses is spinosad. Again, use spinosad-based products with caution and only as a last resort. Never spray when pollinators are active.
6. Spider mites: Minute rose pests that discolor leaves
These super-tiny rose pests may be difficult to spot, but their damage is very distinct. They’re found across much of North America and on most other continents as well.
Measuring just 1/20″ long, you need a hand lens or magnifying glass to confirm spider mites are the rose pests you’re dealing with. Spider mites have 8 legs and spin a fine webbing as shelter. The webbing is easily spied on leaf undersides and between stem tips. If you suspect spider mites on your roses, tap a branch over a sheet of white paper and look for tiny specs crawling on it. Their damage appears as mottled, yellow foliage.
Once spider mites have been confirmed, your first (and best!) line of defense is the many beneficial predatory insects that help control them. Spider mites are a favorite of ladybugs, predatory mites, minute pirate bugs, and big eyed bugs. Again, add lots of other flowering plants around your roses to encourage these good bugs.
Since some chemical pesticides actually stimulate mite reproduction, avoid them completely. If spider mites get wildly out of control, turn to horticultural oil and insecticidal soap, both of which are highly effective after two or 3 applications.
7. Rose scale: Tiny “bumps” that weaken plants
Like other species of this pest, rose scale is challenging to control. This species looks like white or grey-white bumps along the stems. The thick, crunchy shell of rose scale makes it resistant to most pesticides. Rose scale overwinters as eggs that hatch in the spring.
Damage from this pest of rose bushes is weak growth and restricted flowering. It’s easy to see the tiny bumps on the stems of your roses when scale is present. Often the leaves are covered with gray-black sooty mold, which grows on the excrement of the rose scale insects.
Rose scale is most vulnerable about four weeks after they hatch (typically in mid June) because at that time, their bodies are soft, having yet to form the hard coating (a life-stage called the crawler). A properly timed application of horticultural oil suffocates them in their crawler stage. You can also spray during the dormant season to smother overwintering eggs.
8. Rose cane borers: Critters who cause cane dieback
Rose cane borers are another pest of roses, though they aren’t as problematic as most others. Symptoms of this pest are wilted cane tips, yellowing foliage, and occasionally, a dead cane. Rose cane borers tunnel into the cane, typically after it’s pruned. You’ll know they’re at work if you spy a hole in the end of a cut rose cane. There are a few different insects that bore into rose canes, depending on where you live. The treatment for these different insects is the same.
The damage rose can borers cause is often insignificant and really nothing to worry about, unless they’ve managed to kill an entire cane. If you’d like, simply cut off the damaged cane, toss it in the trash, and call it a day.
Building a mixed rose garden to limit pests
Despite all of these different rose pests, roses are still wonderful plants to grow. Always choose disease-resistant, low-maintenance varieties. As you now know, deterring rose pests starts by planting a lot of different flowering plants in your garden to help encourage natural rose pest control via beneficial insects. Instead of planting only roses, aim for a mixed habitat including lots of different species of flowering plants with varied flower shapes, colors, and bloom-times. The more diversity you have in your landscape plantings, the healthier they will be! And, if the pests still show up to make dinner of your roses, consider yourself armed with the know-how to use safe, effective organic rose pest controls, instead of systemic chemicals. Happy rose growing!
Do you grow roses? Tell us your favorite varieties in the comment section below!