Common Insect & Mite Pests of Roses
Common Insect & Mite Pests of Roses
Aphids: Many species of aphids or plant lice, including the rose aphid, attack roses. Aphids are small, soft-bodied winged or wingless insects about 1/25 to 1/8 inch long with relatively long legs and antennae. Species vary in color from black, green, yellow to even pinkish. Some aphids lay eggs; others give birth to live young that mature in 7 to 8 days. Because aphids breed continuously, populations grow quickly, especially in cool weather.
Aphids usually live together on buds, the underside of leaves or in the plants’ growing tips. They suck out plant sap and excrete a sweet, sticky substance called “honeydew” that collects on leaves and stems. A black fungus called sooty mold grows on honeydew, making it look ugly and reducing photosynthesis. Plants heavily infested with aphids appear wilted. Some aphid species cause leaves to yellow or drop from the plant; other species stunt and curl young leaves. Heavily infested buds may fail to open, be deformed or produce small blossoms.
Leafhoppers: Leafhopper species are about four times longer than wide. When full grown, they range from 1/4 to 1/2 inch long. Adults vary in color from gray to yellow and green; some species have patterned markings. The immature forms (nymphs) resemble adults but are lighter in color and lack wings. Both adults and nymphs can injure roses. Some species feed on tender stems and leaf petioles; others, such as rose leafhoppers, feed on the underside of leaves, causing whitish stippling. In Texas, leafhoppers attack roses from early spring until late fall.
Scale insects: Several scale insects occasionally attack roses, but the most damaging is rose scale. Small and soft-bodied, scale insects secrete a material that forms a shell or “scale” over the insect itself. Female rose scales are round and dirty white. Males are elongate and snow white. When mature, these insects insert their mouthparts into the plant tissue and remain there, protected under their scale covering, for their entire life span. Females deposit eggs beneath the old scale covering.
When the eggs hatch, the young, six-legged scale insect “crawlers” disperse throughout the new tissue and attach themselves to the plant. Heavily infested canes may become encrusted in the scales. Scales become most abundant under high humidity and reduced sunlight. They not only spoil the plant’s appearance, but also greatly reduce plant vigor.
Whiteflies: Adult whiteflies are small, white, soft-bodied insects. Weak fliers, they resemble tiny snowflakes fluttering about a plant. Immature whiteflies attach to the underside of leaves and resemble scale insects. Both immature and adult forms feed on roses, leaving yellow spots on the leaves. Heavy infestations can cause defoliation. Much like aphids, whiteflies secrete honeydew, causing plants to be covered with a black sooty mold.
Spider mites: Although several species of spider mites attack roses, the most common is the two-spotted spider mite. Mites are tiny, scarcely visible without magnification. Their color varies in shades of yellow, red and green marked with two darker spots on their backs. All developmental stages of spider mites usually live on the underside of the leaves, but may be found elsewhere on heavily infested plants, which they may cover with a fine web. Female mites lay clear, spherical eggs on the underside of leaves. Eggs develop into adults in 5 to 20 days, so populations grow quickly, especially in hot, dry weather.
Spider mites rupture plant cells with their mouthparts and suck the juices, producing feeding punctures that look like tiny light-colored spots, giving leaves a stippled appearance. Leaves of heavily infested plants turn yellow, then brown and eventually fall from the plant.
Thrips: Common species on roses include flower thrips, onion thrips and tobacco thrips. Thrips are extremely small, soft-bodied insects less than 1/16-inch long. Some are yellow to golden; others almost black. Females lay eggs in plant tissue. After hatching, immature stages (larvae) develop through several stages, completing their life cycle in about 3 weeks. Migrating adult populations, particularly in late spring, damage roses most. Thrips feed predominately on pollen, but also attack tender plant tissue, rasping the surface tissue from
leaves, buds and petals. Recently injured tissue looks silvery. Heavy infestations result in discolored, deformed growth and blemished, deformed flower petals.
Leaf-feeding beetles: Several species occasionally feed on rose plants, chewing plant tissue from leaves, buds and petals. Rose chafers and June beetles are brown; rose leaf beetles are small and metallic green; and twelve-spotted cucumber beetles are 3/8 inch long and greenishyellow with black spots.
Caterpillars: Many species of caterpillars, the immature stages of moths, can be incidental pests of roses. Although most feed on leaves voraciously, only a few damage or defoliate plants extensively. Leafrollers are small, palegreen black-headed caterpillars that produce leaf mines when small and later feed inside leaves they have rolled up and tied with silk. Leaf tiers also draw several leaves or parts of leaves together with silk.
Grasshoppers: Several species of grasshoppers feed on rose leaves, buds, flowers and stems. Winged adult grasshoppers are difficult to control in the times of year they migrate to rose plantings from surrounding vegetation where they developed.
Leaf-cutter bees: These solitary bees nest in burrows and hollowed twigs and stems. Adult females cut circular to elongate pieces of leaves from roses to build walls and partitions of nesting cells where their young develop. Cells are provided with nectar and pollen collected from flowers as food for the larvae.
Indirect pests of roses: Many insects in and around rose plantings should be controlled when they become numerous enough to be a nuisance. These pests rarely injure established rose plants in the landscape. These are:
- Red imported fire ants
- White grubs
- Snails and slugs
- Centipedes and millipedes
- Crickets
- Fungus gnats and
- Springtails
