Aphids top this list because they are the most frequent rose pest. They love to nestle into the buds and shoots of rose bushes. While low to moderate levels of aphids will not do much harm to your roses, you need to keep an eye on how they spread. High numbers of aphids will produce a lot of honeydew. This substance encourages mold growth and will eventually cause your rose leaves to blacken. You may notice that your flowers shrink in size and the buds may even be killed. Lady beetles and syrphid flies are the natural enemies to aphids and will keep the population under control. You can also spray the plant with water or insecticidal soap. Aphids are usually a problem during spring and early summer. Unless you have a really heavy infestation, it is uncommon to have to use insecticides against them.
2. Spider Mites
If you notice your rose leaves are stippled or dried up and dropping to the ground, you may be infested with spider mites. These little insects are so tiny you may need a magnifying glass to see them. They like dry, dusty conditions. You can control spider mites by providing a little more water to your roses to cut down on dust.
3. Fuller Rose Beetles
Adult Fuller Rose beetles will eat at the flowers and leaves on your roses. Look for ragged edges on your foliage and blooms. They eat at night and hide all day on the underside of leaves. The best way to control them is to pick them by hand, since pesticides are not effective against them.
Thrips leave brown streaks down the flower petals. When roses are planted close together thrips can become a big problem because it is easy for them to move from plant to plant. They like light colored or white roses best. Pesticides are only effective against thrips during their developmental stage. If you notice a thrip problem, clip and dispose of all infected blossoms.
Some caterpillars do eat rose leaves. If you find any, remove the rolled up leaves and cut off any buds that have been damaged. Usually, caterpillars won't harm the plant enough to make any permanent damage.
5. Rose Slug
The rose slug is actually the larva of a sawfly. They look like caterpillars since they have legs. Wash them off with a good spray of water or let one of their natural enemies do the dirty work for you.
7. Leafcutter Bees
Leafcutter bees cut semi-circular holes in rose leaves to take back to their nests. There is really no way to fight them other than killing them. It is recommended by many sources not to kill bees since they do all the pollinating, so you may just need to put up with this.
8. Rose Curculio
Yellow and white roses are the preferred targets of rose curculios. They are only about a quarter inch long, but that doesn't stop them from punching holes in buds and flowers. The larvae eat developing buds, so the blossoms are killed before they even have an opportunity to open. You can get an insecticide against rose curculios at your local garden center.
9. Flat headed Borers
Flat headed borers will kill the canes. With enough damage, they can kill the entire plant. Remove any infested material and keep your roses healthy by not over pruning in the summer. Make sure your roses get enough water.
10. Scale Insects
Scale also poses a threat to your rose canes. Scale insects have armored scales. When you see them on a plant they look like gray round or oval bumps. They really don't move since they have no legs, so once you see them, you know where they are. The best way to combat scale insects is to prune infected canes and put pesticide oil on the canes that are left.