Roses are prized for their beauty and color, but when infested with insect pests, severe cosmetic damage may occur. Due the rose plant's susceptibility to a variety of insects, identify different insects based on symptoms and control methods for successful prevention of problems. Because certain insects may carry transferable diseases, keeping insects out of the rose garden is your best bet for healthy, vigorous plants.
Aphids are insects that infest rose plants; these insects are referred to as sucking pests due to their feeding methods. Also referred to as plant lice, aphids measure 1/25 to 1/8 inch in length and display green, black, yellow or pink bodies, according to the Texas Agricultural Extension Service. Infestations may spread rapidly as aphids continue to breed without pause. Inhabiting undersides of leaves, aphids feed on plant fluids. During feeding, aphids release a sugary substance known as honeydew, which causes further problems as it increases the incidence of the fungal infection sooty mold on rose plants. Look for black-colored mold as a secondary symptom of aphid infestations as well as flowers that fail to bloom or appear malformed, yellowed leaves, leaf drop and stunted growth.
Whiteflies are sucking pests of rose plants. These insects display white bodies; flying around rose plants, they inhabit the undersides of leaves before they reach maturity. Whiteflies feed on plant tissue fluids by sucking on rose plant parts. Like aphids, whiteflies release honeydew and increase the likelihood of sooty mold infections, according to the Texas Agricultural Extension Service. Look for extreme leaf drop and yellow spotted leaves to differentiate this pest from aphids.
Leaf-cutter bees are considered a chewing insect of rose plants. These bees act independently, seeking out roses for shelter where they form temporary residence in hollow twigs, hollow stems and empty spaces within rose plants. Damage is caused by adult females that use the plant for future food and shelter. As suggested by their name, these bees cut sections off of leaves for use in building nests for younger bees, according to the Texas Agricultural Extension Service. Symptoms usually include holes in half-circle formation in leaves. As a food source for the young bees that live within these nests, the adult female bee obtains rose nectar.
Collect and destroy injured plant parts and prune healthy roses of dead canes to prevent hiding places used by insects for habitation. Use a strong stream of water to physically push insects like mites from leaf surfaces. Release beneficial insects such as parasitic wasps like Aphelinus abdominalis that act as predators to whiteflies and aphids, recommends the Texas Agricultural Extension Service. Purchase these "natural enemy" insects from gardening supply sources, such as catalogs. Keep your roses vigorous through proper care as insects often attack weak plants before they attack strong plants.
Choose pesticides formulated for use on rose plants if your infestation is severe enough to warrant chemical control. When in doubt, contact your local county extension agent for a focused control plan. For bee control, apply the chemical carbaryl. For management of aphids, select acephate, azadirachtin or carbaryl. For whitefly infestations, apply chlorpyrifos or acephate, notes the Texas Agricultural Extension Service.