Common Disease Problems
Black Spot: This is a fungal disease that affects leaves. It usually occurs in hot, humid or rainy weather. Black circular spots appear on the upper and undersides of leaves. The outer margins of the circles are ragged. The spots can enlarge and merge. The leaves often fall off the plant leaving the plant defoliated. The damage is often worse on the lower leaves. Burpee Recommends: Plant resistant varieties. Remove all debris from under the plants. Avoid getting the leaves wet. A mulch under the plants will help prevent spores from splashing up.
Botrytis: This fungus causes a grey mold on flowers, leaves, stems and buds. It thrives in cool wet weather conditions. Burpee Recommends: Remove affected plant parts, avoid watering at night and getting water on the plant when watering. Make sure plants have good air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Crown Gall: This is caused by a bacteria and causes galls (masses of plant tissue) to form on roots, root crowns, stems and branches. The galls can interfere with the ability of water to move through the tissue, affecting plant vigor and causing stunted plants. Burpee Recommends: There is no cure for this disease; remove and destroy infected plants.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Rose Rosette: This virus-like disease causes witches’ broom growth on roses. Early symptoms include a red pigmentation on the underside of leaves followed by excessive growth of vegetative shoots that are more succulent than normal and red. The leaves become crinkled and brittle with yellow mosaics and red coloring. The leaves become very small. The plant becomes very susceptible to freeze damage. There may also be a proliferation of thorns. This condition is spread by eriophyid mites. Burpee Recommends: Remove and destroy infected plants. Avoid planting roses near multiflora roses, which are alternate hosts. Control eriophyid mites.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects that can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap. Check with your Cooperative Extension Service for suggestions.
Eriophyid Mites: These microscopic mites cause blistered, rust colored or curled leaves, and spread rose rosette disease. Burpee Recommends: Natural predators are available. Check with your Cooperative Extension Service for suggestions.
Japanese Beetles: Burpee Recommends: Hand pick early in the morning into a bucket of soapy water.
Rose Sawfly: The sawfly larva is green with a tan head and resembles a caterpillar. The larva will skeletonize or create windowpane damage to rose leaves in spring and summer. Burpee recommends hand pick the larva off the leaves. Spray plants with insecticidal soap. Check with your Cooperative Extension Service for other suggestions.
Thrips: Thrips are tiny needle-thin insects that are black or straw colored. They suck the juices of plants and attack flower petals, leaves and stems. The plant will have a stippling, discolored flecking or silvering of the leaf surface. Thrips can spread many diseases from plant to plant. Burpee Recommends: Many thrips may be repelled by sheets of aluminum foil spread between rows of plants. Remove weeds from the bed and remove debris from the bed after frost. Check with your Cooperative Extension Service for pest controls.
My rose leaves are twisted and deformed what causes this? This may be caused by weed killer that has drifted on to the roses. Remove affected stems and keep the plant healthy. If the deformed part of the plant is red and stunted with excessive growth of stems and thorns the problem may be rose rosette.
What are good companion plants to plant with roses? Marigolds, geraniums, basil, mint, alliums, parsley are good companions to help repel pests. To avoid root damage plant at least 18 inches away from the roses.
I would like to transplant my rose to a new spot, when is the best time? The best time to transplant your roses is in late winter or early spring while the plant is still dormant before the new growth starts.
Why won’t my rose bloom? There are several reasons why your rose may not be blooming including: not enough sun, too much fertilizer, the soil pH is too low or too high or the plant does not have enough foliage and cannot make food for itself.
What roses produce the best rose hips? All roses produce hips but the best hips come from Rosa rugosa.