Aphids are the most common pests that affect roses. Other common pests that affect roses include Japanese beetles, spider mites, rose midges, thrips and sawflies. Gardeners consider leaf cutter bees to be pests because they cut perfectly round semicircles out of the edges of rose leaves. However, these bees are necessary pollinators and the damage they inflict is strictly cosmetic. Therefore, gardeners should ignore these bees.
Other pests, however, can infest and stunt the growth of rose bushes. Aphids, which are green, red or black, are merely nuisances in small numbers, but a severe infestation can damage new rose shoots and cause them to become malformed. The honeydew aphids produce can also feed black mold, which blackens the leaves of rose bushes. Gardeners can release beneficial predators, such as lady beetles or lacewings, to keep aphids under control. Other control options include using insecticides or removing the aphids from the roses with a heavy stream of water.
Japanese beetles are dangerous even in small numbers because of their extensive appetites. Their ability to fly also makes it difficult to effectively kill them with insecticides. Gardeners should avoid Japanese beetle traps, which can often attract even more beetles to the area.
Rose midges lay their eggs in rosebuds and new shoots of rose bushes. The larvae eat the plants and drop into the soil below to pupate. To control an infestation, gardeners should trim away infected areas, use insecticides and use a ground cloth to collect the larvae before they can enter the soil.