Greenhouse-grown roses are more susceptible to insect infestations than outdoor roses. Antique varieties and shrub roses have fewer pest problems than hybrid roses. Some insects, such as ladybugs and preying mantis, are beneficial to roses. Preventative care is the first step to good insect control. Early detection is helpful in planning pest control methods. Make sure roses grow in healthy, humus-rich soil and are fed with organic compost. Companion planting is also an effective deterrent to rose pests.
Inspect and Identify Pests
There are two main categories of insects which harm roses,sucking and chewing. Early detection of insect problems is the best preventative. Frequently inspect the underside of your rose leaves for insect damage. Learn to look for discolorations and holes in the leaves, stems, and flower petals.
Sucking insects insert their mouths into a rose plant, ruptures the cells and sucks out the cell contents. The plant is weakened. Sucking insect pests include aphids, leafhoppers, scale insects and whiteflies. They cause symptoms such as yellow and brown discoloration and dead spots on leaves. Other symptoms are a wilted appearance, curled leaves or petals and “honeydew” residue. This sticky residue attracts a sooty mold.
Chewing insects eat the leaves and flowers of rose plants, causing unsightly growth and weakness to the plant structure. Caterpillars, beetles, grasshoppers, and leaf-cutter bees are chewing insects. Symptoms they cause include holes in leaves and stems, discolored areas, severed stems and leaves, stem wilting and semi-circular holes on leaf edges.
Aphids are a small, soft-bodied insect with relatively long legs and antennae. They are a very common problem for roses, sucking out the plant's sap. Aphids multiply rapidly and live together in groups on rose buds and the underside of leaves. Their population increases in cold weather.
Spider mites leave tiny light-colored spots and a stippled appearance on rose leaves. Heavily infested plant leaves turn yellow and brown and then fall off. Spider mites come in yellow, red and green, with two darker spots on their backs. Spider mites cover the rose plant with a fine web. Companion plants which deter spider mites are coriander and dill.