Roses are the divas of the flower garden. With their graceful beauty, rainbow of colors, and heady scent, they are undisputed superstars of the landscape. But, like any diva, they also can be a tad, shall we say, difficult. Here we list eight common rose problems, how to spot them, and what to do.
1. Black Spot
Diplocarpon rosae
What it is:
A fungus seen most often after a long, warm spring but can occur anytime the weather is hot and humid.
What it looks like:
Leaves become covered in black spots ringed in yellow eventually covering the whole leaf, which often will then fall off. When infected, the plant will flower less or not at all and eventually may die.
What to do about it:
Commercial fungicides or home mixtures of baking soda and/or dish soap can help, but these are usually better used as preventatives than in treating the disease once it takes hold. Pick off any leaves as soon as signs of black spot appear and dispose of them far away from the garden to stop the disease spread.
2. Rose Aphids
Macrosiphoniella rosae
What it is:
Tiny green sucking insects that feed on the juices of the plant’s new rose growth.
What it looks like:
Numerous bugs, each about the size of a half grain of rice, swarming on the buds, leaves and green stems of the roses.
What to do about it:
Rinse the insects off the roses with a hose anytime you see them, daily if necessary. Spraying after a wash with insecticidal soap may prevent their return. Several beneficial insects
attack aphids; planting a mix of perennial flowering plants near your roses can help attract these.
3. Powdery Mildew
Podosphaera pannosa
What it is:
A fungus that occurs in dry, cool weather or in the shade.
What it looks like:
A gray-white powdery substance on the new growth and buds of the rose. May cause leaf drop and stunted flower development.
What to do about it:
Commercial fungicides are available, but a spray made of diluted milk has been shown to be equally effective. (Mix in a 60/40 ratio of water to milk to create a spray). As with other fungal diseases, remove any affected leaves as you see them and dispose of them far from the garden.
4. Japanese Beetles
Popillia japonica
What it is:
A lovely, but destructive bronze and green metallic beetle that feeds on roses (and many other plants). An infestation of Japanese beetles can quickly defoliate a plant.
What it looks like:
Japanese beetle infestations can come on quickly and are very noticeable because of the large number of insects that appear on all parts of the plant.
What to do about it:
Japanese beetles are extremely hard to control. The best method is to knock them off by hand into a bowl of soapy water. You may have to do this every morning until the infestation subsides.
5. Rust
What it is:
One of several fungi from the Phragmidium species.
What it looks like:
Orange spots on leaves progressing to brown and yellow leaves and leaf fall.
What to do about it:
Increase air circulation around diseased plants by pruning out the centers, keeping weeds pulled and trimming back surrounding plants.
6. Rose Slugs
Allantus cinctus
What it is:
The rose slug is not actually a slug, but a larva of the sawfly family whose body secretes a slimy substance. They feed on leaves, leaving them skeletal at first, but eventually devouring the entire leaf.
What it looks like:
Yellowish green, worm-like larvae up to an inch long.
What to do about it:
Treat with water washes and insecticidal soap, just as with aphids.
7. Rose Mosaic Virus
Ilarvirus species
What it is:
Two strains of virus can lead to mosaic virus, the prunus necrotic ringspot virus or the apple mosaic virus. Both can be spread in the nursery when a rose is being propagated.
What it looks like:
Sometimes, but not always, the infected plant shows a yellow mosaic pattern on the leaves. Often the only symptom is a decline in the plant’s vigor and its eventual death.
What to do about it:
Because this disease spreads during propagation, the only preventative is to buy plants certified virus free.
8. Thrips
Frankliniella species
What it is:
Tiny green-yellow insects.
What it looks like:
Thrips are often hard to see on the plant without using a magnifying glass. Their presence is marked, however, by the appearance of browning and curled leaves along with distorted rose buds that do not open.
What to do about it:
Some beneficial insects, like the pirate bug, feed on thrips. However, often an insecticide will be necessary to control an infestation. Make sure the one you choose is formulated especially for thrips.
Prevention Tips
Many of these rose problems can be nipped in the bud—or before the bud—by choosing the right rose for your location or one that is resistant to diseases or pests that frequent your region. Also, giving your rose the best start by planting it in a sunny location and providing ample water and fertilizer will help greatly in stopping these problems before they start. Check out our guides on choosing roses and planting roses for more information on both these topics.
If this list makes you feel like growing roses outdoors is too daunting a task, you can enjoy miniature roses indoors—the best way to get your rose fix without the expense or trouble of a full-blown rose garden.
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