Climbing roses can be a beautiful addition to any garden when they are healthy and free from pests. But like all roses, climbing roses are susceptible to numerous diseases, pests and other disorders. To reduce the frequency of problems with climbing roses, choose varieties that are suited for your area and that are resistant to common diseases and pests. Plant roses in full sun in rich, well-drained soil and water regularly with drip irrigation or early in the morning. A little time and effort will ensure your climbing roses are at their best all year.
Powdery mildew is a fungal disease that affects the leaves, shoots, buds and petals of climbing roses. White or gray powder causes distorted growth and early dropping of infected plant parts. Apply a fungicide labeled for powdery mildew on roses in the spring to prevent the disease. Spray horticultural oil on infected roses to eradicate the disease. Another fungal disease, downy mildew, causes angular brown, purple or red spots on the infected leaves of climbing roses. As the disease progresses, the leaves turn yellow and drop off. Control of downy mildew with a fungicide is difficult. Remove and destroy infected plant parts to control the disease.
2. Other Fungal Diseases
Anthracnose affects old-fashioned climbing roses more than other types of roses. Brown, purple or red spots appear on infected leaves. The centers of the spots turn gray or white, and the margins of the spots turn dark red. No chemical control of anthracnose is available. Remove and destroy infected plant parts. Black spot is common on climbing roses. The fungus causes black spots with feathery margins on infected leaves. Apply a fungicide labeled for black spot on roses or use horticultural oil. Botrytis blight causes spots on infected buds and petals. Woolly gray fungal growth forms on decaying plant tissue. Large splotches form on canes, and twigs die back. Remove and destroy infected plant material.
Aphids are extremely common pests on roses. They prefer tender new growth, such as buds or shoots. Slight infestations usually do not cause significant damage. Severe infestations produce large amounts of honeydew that encourages the growth of sooty mold. The mold blackens the leaves and may cause distorted growth and reduced flowering. Use a strong spray of water to wash aphids off climbing roses or apply insecticidal soap or neem oil to kill them. Apply a systemic pesticide for aphids on roses for severe infestations. Beetles chew on the foliage, leaving ragged holes or notched edges. Remove beetles by hand or use a sticky material on the canes to catch the beetles. Chemical control is ineffective due to their life cycle. Bleached or spotted leaves are symptoms of damage by spider mites. Use insecticidal soap, horticultural oil or neem oil to eradicate scale insects. Brown streaks and distorted growth on flower petals are signs of thrips. Remove and destroy the damaged blooms; chemical control is difficult due to the pests' life cycles.
4. Abiotic Disorders
An abiotic disorder refers to damage caused by environmental problems, nutrient imbalances or chemical injury. Sunburn caused by too much direct sunlight or reflected light can cause blackened areas on the canes. Damage by freezing temperatures can result in dead flowers, stems and canes. Nutrient and micronutrient deficiencies can cause yellow foliage and poor growth. Too much of a nutrient results in poor growth with no leaf damage. Damage from a small dose of herbicide can cause leaves to curl, cup, turn yellow or remain small. The plant may outgrow the damage from minor exposure, but a larger dose of herbicide can kill the plant.
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