Why Are Rosebush Stems Yellow?

Disease

• Most diseases cause the leaves to yellow or become spotted, although in severe cases, the stems may yellow too. Look for small creamy or tan bumps, known as galls, or brown to red cankers on the stems or near the base of the plant. If cankers girdle the plant, the stems may turn yellow and the entire plant may die. Remove plants infected with crown gall. Prune out cankers and treat infected plants with a fungicide.

Insect Pests

• Many insects, such as Japanese beetles and leaf cutter beetles, cause fairly obvious damage to plants in the form of eaten leaves. Aphids and leaf hoppers, though, suck the juices from leaves and stems, causing them to become distorted, wilted or yellowed. Look under the leaves for tiny green, brown or red insects. Another sign of infestation is sticky leaves and stems, caused by honeydew secreted by the insects. Spray the rose bushes with a steady stream of water or with an insecticidal soap to treat leaf-sucking insects.

Nutrient Deficiencies

• Too much fertilizer can promote leafy growth at the expense of blooms, but insufficient nutrients can cause yellowing leaves, or in severe cases, yellowing stems. Nitrogen deficiencies cause the entire leaves to turn pale yellow, while iron or manganese deficiencies cause yellow leaves with green veins. Treat plants with a balanced fertilizer for roses. Treat iron deficiencies with a foliar iron supplement or by lowering the pH of the soil so roses can absorb more iron. Herbicide injuries can cause similar symptoms and occur when herbicides drift from other plants or come in contact with the soil the roses are growing in. Most roses will recover from herbicide damage. Water and fertilize them to promote good health.

General Recommendations

• Roses require more care than some plants to remain healthy. Start by planting disease-resistant varieties adapted to your area. Plant them in full sun and space them so air circulates freely. Prune roses in late winter to remove dead growth. Remove diseased portions anytime, disinfecting pruning tools in a chlorine bleach solution between cuts to prevent the spread of disease.