Rose Pest ID and Control

Look up symptoms, identify culprits, and learn about environmentally friendly controls. If you choose to use a pesticide, be sure it is labeled for roses and follow directions carefully.

Leaf Symptoms \| Flower Symptoms \| Shoot and Cane Symptoms \| Whole Plant Symptoms
Leaf Symptoms Examine leaves carefully. Look for holes, general discoloration, spots. Note size, shape, and edges of holes, and color or patterns of spots. Leaves appear eaten \| Large areas of foliage discolored \| Spots on leaves \| Other symptoms
	Symptom	Suspects	What to Look For	Controls
Leaves appear eaten
	Ragged holes	Slugs and snails	Look for silvery slime trail.	• Hand-pick slugs in the cool of morning. • Use iron-phosphate baited traps. Notes • Start control measures early in the season to minimize the slug and snail populations. • Iron phosphate occurs naturally in soil and is a safer choice than metaldehyde bait, which must be kept away from pets and children. • A saucer filled with beer will attract slugs, which then drown. Clean and refill frequently. View photos.
		Caterpillars	Look for dark-colored fecal pellets (droppings). Two caterpillars that attack roses are tobacco budworm and leaf roller larvae.	• Hand-pick caterpillars. • Use B.t. (Bacillus thuringiensis) • Use a spinosad-based insecticide. • Use a butterfly guide to ID larvae of desirable species. Notes Remember that caterpillars are butterfly and moth larvae, so use controls judiciously so as not to harm desirable insects. View photos.
		Japanese beetles	Adults are metallic green with reddish bronze wing covers. Visit the garden in the morning to look for beetles -- they're sluggish in cool temps. Japanese beetles often "skeletonize" leaves, eating the foliage between the veins.	• Hand-pick beetles in early morning and squish or drop into soapy water. • Control grubs (larvae) in the lawn with beneficial nematodes. • Use a spinosad-based insecticide. • Protect prized plants with mosquito netting. Notes • Japanese beetles secrete a pheromone that attracts other beetles. By hand-picking beetles daily you can minimize this phenomenon and prevent a buildup. • Milky spore disease can be effective in warm climates, less so in colder regions. • Japanese beetle traps will catch beetles, but because they are baited with pheromones they can actually attract beetles to your yard. If using, place them in groups away from desired plants. View photos.
		Rose chafers	Adult beetles are yellowish brown with a brown head, 1/3 to 1/2 inch long.	• Hand-pick beetles in early morning when they're sluggish. • Control grubs (larvae) in the lawn with beneficial nematodes. • Use a spinosad-based insecticide. • Protect prized plants with mosquito netting.
	Perfectly round or semicircular holes	Leafcutter bees	Adults are about the size of honeybees but have darker bodies.	Leafcutter bees are important pollinators and are NOT pests. The damage they cause is negligible, and their sting is very mild.
	Leaves appear shredded or torn	Mechanical damage, such as from hail or string trimmers	Leaves may appear torn, rather than eaten. Heavy winds, torrential rain, and hail will tear plant leaves, so if you've had a spell of severe weather suspect this as a cause. String trimmers can cause similar damage.	• Remove severely damaged leaves; otherwise, leave in place so plant can continue to photosynthesize. • Tie long canes to a trellis or other support to prevent them from whipping in the wind. Notes • Plants will usually outgrow damage to foliage. • Protect plants from string trimmers by surrounding them with mulch. • Cover or otherwise protect precious plants when storms threaten. View photos.
Large areas of foliage discolored [back to top]
	Symptom	Suspects	What to Look For	Controls
	Distorted, discolored, dying foliage, especially on an isolated section of the plant.	Herbicide damage. Wind may have carried the chemical to the plant.	If one section of the plant is affected and if you've recently applied herbicide nearby, suspect this as a cause.	• Remove damaged foliage. Systemic herbicides may kill entire plant. • If one side of a plant mysteriously dies overnight, suspect herbicide damage.
	White or gray powdery substance on leaves	Powdery mildew	Plants often look as though talcum powder has been sprinkled on the foliage. The disease is most common on the upper surface of leaves. Severely infected leaves may turn yellow.	• Powdery mildew spreads in dry weather; hosing plants off every few days will wash off spores. (Do this by midday so foliage is dry by evening.) • Use a spray that contains neem or potassium bicarbonate. Notes • Minor infection won't harm plants, but a serious attack can cause stunting and misshapen blooms. • Treat plants with a dormant horticultural oil spray to prevent spores from overwintering. • Choose varieties resistant to powdery mildew. • Plant roses in full sun and space adequately to endure good air circulation. View photos.
	Overall bronze or silvery tint to foliage	Spidermites	Spray a fine mist of water on the new growth; if spider mites are present, the droplets will cling to the fine webbing.	• Hose off plants frequently, including the undersides of the leaves. • Treat a bad infestation with an insecticide containing neem or insecticidal soap. Notes • Spider mites flourish in hot, dry conditions. Look closely at the undersides of the leaves and you may see the red, pinhead-sized mites. • Many insects feed on spidermites; encourage these predators by using pesticides (even organic ones) judiciously. View photos.
	Symptom	Suspects	What to Look For	Controls
	Areas between veins are translucent or tissue paperlike.	Roseslugs (sawfly larvae)	Examine upper and lower surface of leaves for 1/4 - 1/2" caterpillar-like larvae. Roseslugs scrape the leaf surface, often leaving a "windowpane" of thin tissue.	• Roseslugs are easiest to control if you start early in the season. • Inspect plants frequently and handpick or wipe off larvae, or spray undersides of leaves with a strong stream of water. • Repeated sprays of horticultural oil, insecticidal soap, or neem will help manage bad infestations. • Use a spinosad-based insecticide. Notes Roseslugs are the larvae of the sawfly. They're neither true caterpillars (the larvae of butterflies and moths) nor slugs. So controls targeting caterpillars, such as B.t., and slugs, such as iron phosphate bait, won't control roseslugs.View photos.
	Yellow leaves	Insufficient water	Check soil moisture	Both too little and too much water can cause yellow foliage, especially in container-grown plants.
		Nutrient deficiency	If plants (especially container-grown ones) haven't been fertilized in several months and there's no sign of insect damage, suspect a nutrient deficiency.	• Nutrient deficiencies can cause various symptoms, from weakened growth to yellowing leaves. • Fertilize indoor and container plants with a fertilizer that includes micronutrients; organic fertilizers are a good choice. • Have garden soil tested for nutrients and pH and adjust accordingly. An annual application of compost helps boost nutrient levels.
		Disease	Diseases usually show up as patches of discoloration.	Rule out above factors before suspecting disease.
	Red foliage on new growth	The leaves on many roses emerge dark red.	If leaves are shiny and healthy, the leaves are fine.	No action necessary; as the foliage matures it will turn green.
Spots on leaves [back to top]
	Symptom	Suspects	What to Look For	Controls
Managing Diseases These tips apply to the following 4 fungal diseases: • Plant roses in full sun and space properly to promote good air circulation. Keep rose bed weeded. • Apply water to soil to keep foliage dry. • Many diseases overwinter in plant material and debris, so rake and remove fallen leaves and old mulch in fall. Prune out dead or dying canes. • Properly water, fertilize, and mulch plants to maintain vigor. • If spraying is warranted, look for organic fungicides that contains sulfur, neem or potassium bicarbonate, or Bacillus subtilis
	Rust-colored spots or bumps	Rust	Orange, sometimes powdery pustules on undersides of leaves and occasionally on canes; yellow spots on upper surface of leaf. See Managing Diseases above.
	Irregular yellow to purplish brown spots on upper leaf surface	Downy mildew	Irregularly shaped, reddish-purple, angular blotches. See Managing Diseases above.
	Black or dark brown spots, often accompanied by yellowing leaves	Black spot disease	The spots caused by this fungal disease have fuzzy, irregular edges. See Managing Diseases above.
	Small dark spots develop on upper leaf surfaces, sometimes with a lighter center	Anthracnose	Spots may initially appear reddish-purple to dark brown; eventually the center dries out and turns lighter brown. Severe infections cause leaf yellowing and defoliation. See Managing Diseases above.
Other symptoms [back to top]
	Symptom	Suspects	What to Look For	Controls
	Narrow, winding paths or tunnels on leaves	Leaf miners	Try splitting the leaf open to look for the small larvae.	Leaf miners are the larvae of a number of insects. They live and feed between the upper and lower leaf surfaces, making them difficult to control. Fortunately, the damage they cause is mostly cosmetic.
	Sticky substance on leaves; leaves may be distorted or discolored	Aphids	Look for slow-moving aphids congregating on new growth. They are about 1/8" long and oval-shaped.	• Frequent hard sprays of water will dislodge aphids. • Encourage beneficial insects, such as ladybugs, which eat aphids. • Aphids can transmit harmful plant viruses. • Avoid overfertilizing, especially with a high-nitrogen formula, since this encourages a flush of succulent new growth to which the insects are attracted. Notes Aphids, scale, and whiteflies are similar in the way they attack plants: They suck on plant juices and leaves become discolored and distorted. The insects all secrete a sticky "honeydew," which is sometimes covered with black sooty mold. Control the insects, and you control the sooty mold. View photos.
		Scale	Scale look like tiny turtle shells attached to stems and leaves, especially the undersides of leaf veins. They don't move, and you can scratch them off with your fingernail.	• Gently scrape scale off. • Spray with horticultural oil. • Scale insects are soft-bodied; they secrete a material that forms a shell over the insect itself. • Avoid overfertilizing, especially with a high-nitrogen formula, since this encourages a flush of succulent new growth to which the insects are attracted. Notes Aphids, scale, and whiteflies are similar in the way they attack plants: They suck on plant juices and leaves become discolored and distorted. The insects all secrete a sticky "honeydew," which is sometimes covered with black sooty mold. Control the insects, and you control the sooty mold. View photos.
		Whiteflies	Tap the foliage; if whiteflies are present you'll see a flurry of tiny, white, mothlike insects flying away.	• The damage whiteflies cause is often mostly cosmetic; however, they can transmit harmful plant viruses. • Spray plants with a stream of water from a garden hose may dislodge the majority of the pests. • If necessary spray with insecticidal soap. • Whiteflies are challenging to manage because they fly away when disturbed. • Yellow sticky traps hung in the shrubs can trap some whiteflies, but the traps can be unsightly. • Avoid overfertilizing, especially with a high-nitrogen formula, since this encourages a flush of succulent new growth to which the insects are attracted. Notes Aphids, scale, and whiteflies are similar in the way they attack plants: They suck on plant juices and leaves become discolored and distorted. The insects all secrete a sticky "honeydew," which is sometimes covered with black sooty mold. Control the insects, and you control the sooty mold. View photos.
	Leaves stunted, distorted, and/or discolored	Viruses	There are many different viruses causing different symptoms.	• Viruses cannot be treated. Remove affected roses and replant with virus-free stock. • Rule out other diseases and disorders before replacing plants. • Viruses are usually transmitted by aphids, leafhoppers, and other insects. Controlling these insects may control spread of the virus.
	Leaves stunted, distorted, and/or discolored	Aphids, scale, or whiteflies	Look for sticky honeydew	See above
	Symptom	Suspects	What to Look For	Controls
	Cottony white masses on underside of leaves, and esp. in leaf axils	Mealybugs	You might also see the sticky honeydew secretion if infestation is severe.	• Spray with horticultural oil. • Encourage beneficial insects. • Avoid overfertilizing, especially with a high-nitrogen formula, since this encourages a flush of succulent new growth to which the insects are attracted.
	Foliage wilted	Dessication; stem damage; root damage	Dry soil or dry, windy weather can cause wilting.	Anything that affects a plant's ability to take up water can cause wilting. Check soil moisture first. Note that even some healthy plants will wilt slightly during very sunny, hot, and/or windy days, but will recover at dusk.
			Small holes in stems, especially near the soil line, indicate borers.	Insects, such as borers, create small holes in stems and inhibit water update. If you find holes, try inserting a paper clip into the hole to impale and remove the caterpillar.
			Overwatering can damage roots, as can certain diseases.	Overwatering results in root rot. Plant may recover if moved to a spot with better drainage.
			Rule out other options before suspecting diseases	Some diseases affect water uptake. These can be difficult to diagnose.
	Overall lack of vigor	• Insufficient water • Nutrient deficiency • Improper soil pH • Virus		If soil pH (a measure of acidity/alkalinity) is too high or too low, nutrient update is inhibited. If you've recently fertilized and plant is still stunted, test your soil for nutrients and pH.

Flower Symptoms [back to top]
	Symptom	Suspects	What to Look For	Controls
	Flower buds distorted; flower petals flecked with white; flower buds fail to open	Thrips	Look for black specks, especially on the undersides of the leaves. These aren't the actual thrips, they are the thrips' fecal matter, but because thrips are so small these are a good identifier.	• Remove and destroy infected buds. • Encourage beneficial insects. • Thrips lay their eggs inside the plant's epidermis where they're protected from sprays. Still, washing plants every few days with a strong stream of water can reduce the population of adults. • Use a spinosad-based insecticide. • Yellow sticky traps hung in the shrubs can trap some thrips, but the traps are unsightly. • Thrips seem to prefer buds on the verge of opening and are especially attracted to light-colored flowers.
	Buds fail to open or turn brown and die	Rose midges	Look for tiny white larvae at the bases of buds, especially between the petals and sepals.	• Prune off and destroy affected buds. • Spray with a neem- or spinosad-based insecticide. • Rose midge is a fly larva; although it looks like a tiny caterpillar, caterpillar-specific sprays, such as Bt, won't work.
	Buds fail to open or turn brown and die	Balling/botrytis blight	If damage occurs in cool, wet weather and there's no evidence of thrips or midges, suspect botrytis.	The buds of some many-petaled roses fail to open, especially in cool, wet weather. Eventually the buds turn brown or fuzzy gray due to infection by botrytis. Prune off affected buds; when weather warms and dries the flowers should open normally. Some varieties are more prone to balling than others.
	Buds and flowers chewed	Japanese beetles		See description under Leaf Symptoms.
Shoot and Cane Symptoms [back to top]
	Symptom	Suspects	What to Look For	Controls
	Wilting or dying foliage at the top of canes	Borers	Look for a small hole in the center of a pruned cane end.	• Prune the cane below any areas of damage. Put a dab of household glue on pruning cuts. • If you find holes, try inserting a paper clip into the hole to impale and remove the caterpillar. • The larvae of several insects, including sawflies, carpenter bees, moths, and some wasps, are all referred to as borers.
	Foliage along a cane wilts and drops off	Rose scale	Look for small gray or brown bumps along cane and sticky "honeydew" secretions.	• Gently scrape scale off. • Spray with horticultural oil when plants are dormant.
	Round growths up to two inches across at the base of the plant	Galls		• Prune off small gall with a sharp knife or pruning shears, disinfecting tools after each cut. • Crown gall is a disease caused by soil-borne bacteria, which enter a plant through the roots or through wounds at the root area. The gall is the result of abnormal cell growth caused by the presence of the bacteria.
	Mature rose canes die and turn black	Dieback or canker	Problem progresses down an infected cane during growing season.	• Caused by several common disease organisms. • Prune back into healthy green tissue as soon as problem is noticed. • Remove pruned canes from garden area and dispose of them.
	Mature rose canes die and turn black	Winter injury	Problem observed in early spring; does not spread.	• Prune back into healthy green tissue as soon as problem is noticed.
Whole Plant Symptoms [back to top]
	Entire plants trampled overnight	Deer	Many torn leaves and damaged or missing buds and blooms. Twigs appear torn, rather than cleanly cut.	• Repellent sprays can be effective but must be reapplied frequently. • Begin control measures as soon as you see damage to encourage deer to look elsewehere for food. • The only sure-fire way to protect plants is with a deer-proof fence.
	Bite marks on canes; damaged twigs	Rabbits	• Rabbits bite cleanly through twigs so they look like they've been pruned. On larger canes. look for paired tooth marks. • Look for rabbit scat: small, hard, round, pea-sized pellets.	• If gnawing has girdled a cane (damage the entire circumference), cut the cane back to the base. • Repellent sprays can be effective but must be reapplied frequently. • Use rabbit fencing or 1/4" hardware cloth that is at least 18" high and buried 2 to 3 inches in the soil.
	Girdled canes; whole cane dies	Voles	• Vole typically damage bark near the soil line.	• Voles, or meadow mice are stocky, greyish-brown rodents with tiny ears, small eyes, and a relatively short tail. • Repellent sprays can be effective but must be reapplied frequently. • Damage is most severe in winter when food supplies dwindle and the voles are protected from predators while burrowing beneath the snow. Stomping snow around shrubs may deter voles from returning.
	Extensive damage to roses	Woodchucks (also called groundhogs and whistle-pigs)	Look for large (12" to 18" in diameter) entrance holes to their burrows. Usually there's a small mound of soil near the hole.	• Woodchucks are large rodents weighing up to twelve pounds. • Mow weedy areas near plantings. • Frightening groundhogs away from the garden with motion devices (mylar tape, whirlygigs) • Put urine-soaked kitty litter inside all burrow entrances; the strong odor deters them. • Fence them out using chicken wire. Make the fence portion 3 to 4 feet high, and bend the bottom portion of it outtward, away from the garden, so they can't dig under. Leave the top foot unconnected to stakes so the fence bends under the weight of the climbing groundhog.