 to open and the interior of the bud is usually filled with a cob-webby mold. Control is just to cut all infected buds along with several inches of stem and remove from the garden. Other diseases that can affect roses are mosaic, stem canker, and crown gall. They are not usually a problem in clean beds where sanitation is practiced and no fallen debris is allowed to remain. If you suspect a problem with your roses that is not powdery mildew or black spot, call your Extension agent.
Roses are attacked by many insects. The most common in this area are described below. Remember when using pesticides that they are nondiscriminatory, killing even the "good bugs", so learn to identify specific insects and use only recommended pest management for them. Experiment with companion plantings and natural predators. While enjoying your evening walk in the rose garden, be on the lookout for problems and act early.
- Japanese beetles. The Japanese beetle attacks rose flowers and foliage during July and August. This beetle is about 3/8" long with metallic green and coppery-brown wing covers. Japanese beetles can be successfully controlled by commercial traps placed away from the garden to attract beetles away from the roses. Treating your yard and garden in early spring for grubs will help to keep the mature beetle population down during the summer months. If only a few are seen, just hand-pick and destroy.
- Aphids. Several species of aphids occur on stems, leaves, and buds and often occur in large numbers. By sucking the plant juices, they stunt the plants. Consult your local Extension Office for both chemical and nonchemical control.
- Rose Stem Borers. A hole in the end of a rose cane or stem probably indicates the presence of a borer which has burrowed down deep into the stem tissue. Infested stems usually die back and the entire plant can be lost if borers are not controlled. Cut and destroy infested stems, then seal the fresh cut with white glue. Make a habit of sealing the ends of stems whenever you gut flowers to bring into the house or prune.
- Leaf-Cutter Bees. Leaf-cutter bees cut out circular pieces from rose leaves and other plants and save them as food for their young in burrows dug in the pith of rose stems, broken branches, or in plant crevices. The tunneled stems usually die back for several inches. No satisfactory insecticide control is available for these bees, which are valuable as pollinators. Sealing the ends of the canes prevents the bees from entering and tunneling the stems.
- Spider Mites. The two-spotted spider mite and related species such the juices from rose leaves, which soon become stippled. As the injury progresses, the leaves turn brown, curl, and drop off. When mites are abundant, they spin a web over the leaf surface. These mites are almost too small to see without magnification, but if you suspect mites, hold a plain white sheet of paper under the leaves and tap gingerly on the leaf a few times and you should be able to see minute red specks of the paper. Infestations usually occur in hot, dry weather, but can be controlled by drenching the undersides of the leaves every several days with a forceful spray of water from a hose-end nozzle of water wand.