The rose is one of the most widely grown perennial plants across the United States, according to the Oregon State University Extension Service. Roses flourish in areas that offer spring rain, mild winters and sunshine-filled summer days. The very conditions that make a rose bush thrive also allow a wide variety of insects to flourish and plague the plant. The insects normally will not kill the rose, but they do stunt growth damage foliage and ruin flower production.
Aphids thrive on rose bushes from spring to fall. They cluster in large colonies along the stems, leaves and buds of the rose. The insects can cause foliage defects and damage new stems. Aphids feed on the rose by piercing its skin with their mouth in order to suck the sap out. Control aphids through pesticides, predatory insects or simply washing the rose bush regularly using water to remove the colonies.
Scale insects are tiny and secrete a substance that forms a hard shell over their bodies that makes them appear to simply be a scale on the roses. Most have the appearance of simple white flakes on the flower stems. Under their protective covering, the insects grasp the plant's skin with their mouth and suck the sap. Scale insects thrive in high humidity and low light. The insects will cause the plant to loose its vigor and stunt the rose's growth. Pesticide applications control scale insects successfully.
Spider mites are numerous species that appear red, yellow and green. The mites cluster on the underside of the leaves and often leave behind a fine webbing. Spider mites feed on the rose by sucking the sap with their mouths. Leaves of infected rose bushes appear yellow and brown. The leaves fall off in a heavy infestation. Control spider mites by washing the rose bush regularly with water or through the use of pesticides.
Adult thrips attack rose bushes in the late spring to early summer. Thrips are small insects that appear yellow, gold or black. They feed on new plant tissue and pollen. The thrips' mouths cut through the delicate skin of the stems, leaves and buds. Flowers will appear deformed after a thrips attack.
Whiteflies attach themselves to the underside of the leaves to feed on roses. Heavy infestations will cause the rose bush to defoliate. To determine if a rose bush has whiteflies, shake the stems of the bush and watch for the insects to fly outward like tiny white specks. Another indication of whitefly infestation is the appearance of black soot on the bush from the insects' excretions.