10 Common Rose Problems (and How to Fix Them)

Aphids

One of the most common pests that bother roses is the aphid. These tiny, pear-shaped, sucking insects feed on succulent new growth, and their colonies grow quickly. Symptoms of aphid infestation and damage include:

• Plants pucker, and become brittle, and yellow.
• Flower buds and leaves become distorted.
• Aphids secrete a sticky honeydew substance on the leaves.
• Black sooty mold begins to grow on the honeydew.
• Clusters of aphids begin to gather.
• Ants crawl on the plants and feed on the honeydew.

Here's how to eliminate and control aphids:

• Hose off the rose bush with a strong blast of water.
• Spray all areas of the plant, including the undersides of the leaves. You may need to do this multiple times over several days.
• Try a homemade spray remedy to control aphids.
• Use insecticidal soap if water is not controlling the aphids. Completely coat the plant because the soap needs to make contact with the aphid.
• Attract lady beetles to your garden as an organic, natural way to control aphids. Lady beetle larvae are voracious predators of aphids.

Black Spot

Heirloom roses are susceptible to black spot (Diplocarpon rosae), a fungal disease that develops in warm, wet, or humid weather. Black spot spores are tough to eliminate and it only takes about seven hours of warm moisture for them to germinate. You may not see symptoms for several days but act quickly when you see the following symptoms:

• Small black spots appear on the leaves.
• Black spots on leaves become enlarged and ringed with yellow.
• The entire leaf turns yellow and falls from the plant, indicating a severe infection and imminent defoliation.

Here's how to control black spot:

• Start with a thorough fall clean-up of fallen leaves and debris to avoid overwintering of fungal spores.
• Ensure rose bushes are not stressed or growing in poor conditions.
• Give rose bushes full sun, plenty of water, and good air circulation.
• Spray with Bordeaux Mix, neem oil, or sulfur if you see evidence of black spot.

Powdery Mildew

Powdery mildew is a fungal disease that lies dormant until the right conditions appear: hot, dry days with cool, moist nights. Here are the symptoms of powdery mildew in its stages:

• Young leaves will begin to pucker or crinkle.
• Mold forms on the leaves and stems.
• A thin white coating spreads throughout the rose bush.

Here's how to combat powdery mildew:

• Use a homemade baking soda spray as a preventative treatment (it does not work well after powdery mildew is already present).
• Try a homemade milk spray, which can be effective on roses and edible plants such as cucumbers and squash.

Cercospora Leaf Spot

Cercospora leaf spot, sometimes referred to as rose leaf spot, is caused by the fungus Cercospora rosicola. It's a different fungus than black spot, but they share many characteristics. Here are the progressive symptoms of Cercospora leaf spot:

• Spots develop mainly on leaves as small circles of varying sizes.
• Purple halos develop around the spots.
• Spots begin to expand with grayish-tan centers, indicating dead tissue.

Here's how to control the fungus:

• Remove and dispose of affected leaves as soon as you see them.
• Remove all fallen leaves and debris at the end of the season to limit overwintering spores.
• Use a fungicide to offer some control. Instead of a commercial product, try a baking soda or milk remedy.
• Mulch under your rose bushes to prevent spores from splashing up onto the plants.

Crown Gall

Crown gall affects a wide array of plants, including roses. It is caused by the bacterium Agrobacterium tumefaciens and interferes with a plant's ability to take up water and nutrients. This results in poor growth and weak plants that are easily stressed and injured. The bacterium enters the plants through wounds, from pruning, transplanting, or breakage. Here are the symptoms:

• A small growth develops near the soil line on the stem, crown, or roots.
• New crown galls are usually pale colored and somewhat round.
• As the galls enlarge, they become rough, irregularly shaped, and hard.
• They can eventually start to rot away, but they will return.

Take these steps to avoid crown gall:

• Only purchase certified, disease-free roses.
• Always inspect the base of any purchased rose for unusual growth.
• Clean your pruners between cuts with a dilute bleach solution (1 part bleach to nine parts water) or rubbing alcohol.
• Minimize wounds by using sharp pruners, controlling insect pests, and watching the mower and string trimmer.

There is no cure for crown gall. If you have an infected rose, dig it up and dispose of it somewhere other than the compost bin.

Crown gall bacterium overwinters in the plant and soil. It spreads to other plants by splashing water. Do not replant roses in that spot for at least five years.

Japanese Beetles

Japanese beetles are attracted to rose bushes. They congregate in large numbers and quickly cause a great deal of damage.

It's hard to miss these bronze and green metallic beetles. They feed on the leaves and skeletonize them, eventually defoliating the entire plant. They can also devour and distort flowers and buds.

Here's how to manage Japanese beetles:

• Hand-pick them and drop them into a bucket of soapy water. It is the best, though the most tedious method.
• Try to eliminate Japanese beetles while they are still in your lawn in the grub stage. This results in fewer emerging adults, which are very difficult to eliminate.

Rose Mosaic Virus

Rose mosaic virus refers to two viruses: prunus necrotic ringspot virus (PNRSV) and apple mosaic virus (ApMV). It is spread by vegetative propagation of roses (buds, scion, or rootstock), but does not spread from plant to plant. It might only manifest on one cane, but the whole plant is infected and exhibits poor vigor, few flowers, and stunted growth.

The plant may not always exhibit symptoms and it might just decline. However, most infected roses will have one or more of the following symptoms:

• A yellowing mosaic pattern appears.
• Chlorotic (yellow) rings or wavy lines appear and can look similar to leaf miner damage.
• The veins begin to yellow.
• The flower color becomes mottled.

There is no method to control or manage this virus. Cutting out the cane with symptoms is only a cosmetic gesture but the virus remains active. Avoid the problem by buying certified virus-free plants.

Rose Curculios

Rose curculios are reddish-brown weevils with dark snouts. They are only about 1/4-inch long, but cause a lot of damage. Even their small, white larvae cause damage to roses.

Adult rose curculios feed on the flower buds by poking their long snouts inside. They also deposit eggs inside the closed buds. If the flowers open, they will be full of ragged holes.

Here's how to manage these pests:

• Avoid planting yellow or white roses because rose curculios have a preference for those colors.
• Hand-pick them off roses to control their proliferation.
• Remove existing buds if you see buds with eggs inside of them.
• Diligently dispose of garden debris throughout and at the end of the season.
• If you do have a severe problem with them, Use a broad spectrum or organic insecticide to manage a severe problem with rose curculios.

Rose and Pear Slugs

Rose and pear slugs are two different insects, and neither is a true slug. They are the larvae of sawflies, which are small flying insects. They look like slugs because they secrete a slimy substance that covers their bodies. A small infestation isn't worrisome, as the damage is mainly cosmetic. However, a large population can severely weaken the plant. Here's what to look for:

• Rose slugs, or sawflies, are yellowish-green and can grow as large as 3/4 inch long. This type of slug feeds on the leaves of rose bushes, removing soft tissue, and leaving leaves with a translucent appearance between the veins.
• Pear slugs are a reflective greenish-black and a little smaller, at about ½ inch. Although roses are not the preferred food of pear slugs, they will feed on a variety of plants.

Take these steps to manage rose and pear slugs:

• Start scouting for the larvae when taking care of roses in mid-spring.
• Hose off these mid-spring slugs with a good blast of water.
• Neem oil and insecticidal soap are also effective.
• Avoid using any insecticides for this problem because sawfly slugs have many natural predators, including birds, parasitic wasps, and predatory beetles.

Thrips

Thrips are a common insect pest and there are two kinds: flower thrips and chilli thrips. Here's what to watch for:

• Flower thrips cause buds to distort. If the buds do open, you might also see brown streaks on the individual petals. They are slender and brown with yellow wings.
• Chilli thrips leave rose buds dried out and brittle. They also feed on the leaves, causing them to curl upwards or become distorted. They are pale with dark wings.

Thrips are difficult to get under control because they live inside rose buds and their populations grow quickly. This pest is also difficult to control with pesticides. Here's how to best manage thrips:

• Clean up plant litter in the fall because thrips overwinter in garden debris.
• Remove any distorted buds from rose bushes.
• Encourage natural predators, such as pirate bugs and other beneficial insects. Avoid using an insecticide on thrips if these predators are available.
• Use a variety of methods: horticultural oils, insecticidal soaps, and proper horticultural practices for growing and maintaining rose bushes.