Knowing common rose pests and diseases is crucial if you want your roses to grow vigorously. After all, it’s good to know what to look for, because the faster you identify problems, the faster you can treat them.
While rose care doesn’t have to be overly complicated, these garden plants are prone to some complications. Fortunately, most can be treated.
We’ve put together advice on some of the most common ailments that roses can suffer from, to help keep your plants looking their best.
1. Rust disease
A rust It is a fungal disease that causes orange and black spots on the underside of rose leaves and stems. It can also cause the leaves to drop prematurely.
John Negus, gardening expert for Amateur Gardening magazine, advises treatment by spraying the plants with a systemic insecticide and fungicide and then collecting and burning the affected leaves. “The new growth will be healthy,” he says.
You can help prevent it by sprinkling potassium sulfate over the root area of your plants from mid-spring to early fall, he adds. Some modern types of roses are also resistant to this problem, so keep this in mind when choosing plants for your garden.
2. Cicadas
Rose leafhoppers feed on leaf surfaces, creating a finely mottled effect. The damage is worse in long, dry summers, John explains, and often results in premature leaf drop.
One way out is to encourage predatory insects and other creatures on your land, such as birds and ladybugs to help prevent infestations. You can also fight them with pesticides, but leafhoppers are usually not a big problem for roses and in many cases can be tolerated.
3. Withering of the buds
If you’ve noticed that your roses are wilting with brown spots and buds that don’t open properly, it could be a problem called «bud wilt». This is especially common in double varieties and can also affect peonies.
“It often occurs when wet weather is followed by hot sunshine,” explains Christine Walkden, garden specialist at Amateur Gardening.
“The outer petals of rosebuds become scorched and papery, and they distort the inner petals as they open. The bud and flowers can then become infected with gray mold.
“There is no treatment for the problem other than pruning the affected buds,” she continues. ‘You can also help your roses by avoiding watering in bright or hot sun, so try watering in the evening.’
John Negus says that avoiding splashing the flower buds when watering your roses can also help. Planting them where there is good air circulation can also be beneficial in preventing the disease, as any rain that sticks to the leaves and petals will dry out more quickly.
Another way to help is to feed your rose with potassium sulfate in mid-spring and continue monthly through early fall, he adds. ‘Water and it will help the new growth withstand harsh weather conditions.
4. Larvae
“The adult larvae lay their eggs on the tender rose stems, which then break open leaving long scars on the stems,” says John. “Once hatched, the green larvae feed voraciously on the leaves.” Damaged leaves roll inward along their length and remain that way for the rest of the season.
To treat this pest, remove affected stems, remove larvae by hand, or use an insecticidal spray in early summer, carefully following the manufacturer’s instructions. “Don’t spray when the rose is in bloom to avoid harming pollinating insects,” says John.
If the leaves on your roses are already affected, remove them and burn them.
5. powdery mildew
If your rose bushes become covered in a grayish-white powdery coating, they are likely suffering from powdery mildew. It is a common disease caused by the fungus Podosphaera pannosa, which can affect plant vigor. Humidity increases the risk of development, as does water stress.
You can help avoid this problem by making sure you plant your rose in the ideal position. That means providing good air circulation around it, ensuring it gets enough sunlight throughout the day, and making sure the soil retains moisture but drains well.
Treat it by pruning the affected areas and discarding them as soon as you see the problem developing, says the RHS. During routine spring pruning of roses, it is also best to cut back buds showing larger patches of mold around the thorns. You can also treat powdery mildew with a fungicide, following the manufacturer’s instructions.
Via gardeningetc