Pests and Diseases of Roses - Pests

Pests

Insects that affect roses are often considered pests.

• Aphids: (Greenfly) (Order HemipteraFamily Aphididae) Macrosiphum rosae – Likely to be found on new shoots and buds, aphids are soft bodied insects 1-2mm long. Often green but occasionally light-brown, and sometimes with wings, they may cover (in a colony) the complete growing tip of the plant. Aphids are most active in spring and summer and multiply at a prodigious rate feeding on the sap of the plant by piercing the plant cells via a proboscis. In large quantities they may seriously retard the growth of the plant and ruin buds. They are particularly damaging to the new shoots with subsequent damage to the emerging leaves which become malformed with much the same appearance as leaf-curl in peaches.

• Two-spotted mite (Spider-mites or Red spider mite) (Order Acari: Family Tetranychidae) Tetranychus urticae – Previously known as red-spider mite these arachnids prefer the underside of leaves and are difficult to see with an unaided eye. Evidence of their presence is silvering of leaves where the mites have destroyed individual leaf cells. Fine webbing and eggs on the undersides of leaves is further evidence of the presence of Tetranychus urticae.

• Thrips (Order Thysanoptera) – Thrips are slim-winged insects 1mm in length, resembling fine slivers of wood or rice. Preferring light-coloured blooms and often appearing in plague numbers, flowers are often left looking scarred, warped, and lustreless.

• Rose Slugs (Rose Sawflies)- Sawflies are non-stinging wasps (Hymenoptera) in the suborder Symphyta, not flies (Diptera). They lay eggs in plant leaves or stems with a saw-like ovipositor. There are three species that commonly cause damage to wild or cultivated roses: The Bristly Roseslug (Cladius difformis) is found in Europe, Siberia, and many areas of North America. The larvae is pale green, up to 16 millimetres (0.6 in) long, and covered with hairlike bristles all over its body. It looks like a catepillar but that term strictly speaking only applies to the larvae of moths and butterflies. It skeletonizes the underside of leaves, with several generations per year. The European Roseslug (Endelomyia aethiops) is found in North America as well as Europe. The larvae is more slug-like (but not slimy), up to 13 millimetres (0.5 in), and skeletonizes the upper surface of leaves with only one generation per year. The Curled Roseslug (Allantus cinctus) larvae is pastel green on the back, marked on the thorax and abdomen with white dots, and up to 19 millimetres (0.7 in) long. It frequently coils up like a snake. After skeletonizing entire leaves except the main veins, it pupates in the pith of canes, with up to two generations per year in North America.

• Caterpillars (Order Lepidoptera) See also List of Lepidoptera that feed on roses – The tortryx (tortrix) moth Lozotaenia forsterana is a prominent pest of roses, although not the sole pest. The caterpillars are green, up to 15mm long, and can be found boring into buds or within curled leaves. When disturbed the caterpillars move swiftly, dropping to the ground on a fine thread. Damage is chewn leaves and flowers and buds with "shot holes".

• Curculio beetles (Family Curculionidae)

• Japanese beetles (Popillia japonica) - This species, introduced to North America in 1912, is now an endemic pest in the eastern United States. Adult beetles emerge from the ground in early summer and join into swarms for four to six weeks, devouring blooms and skeletonizing foliage on roses and many other garden plants. Japanese beetles can be partially controlled, albeit slowly, by spreading milky spore bacillus on the lawn areas where the larvae live. The popular pheromone-baited traps may do more harm than good by attracting beetles from a wide area.

• Scale insects (Order Hemiptera)

Cottony cushion scale (Order Hemiptera : Family Coccoidea) Icerya purchasi – This scale infests twigs and branches. The mature female is oval in shape, reddish-brown with black hairs, 5 mm long. When mature the insect remains stationary and produces an egg sac in grooves, by extrusion, in the body which encases hundreds of red eggs. The insect causes little damage but produces copious honeydew (frass) that can cause damaging sooty mould.

California red scale (Order Hemiptera : Family Coccoidea) Aonidiella aurantii – A hard scale, orange to orange-pink, the female covering being less than 1.5mm across. Often in plague numbers this scale infests upper surfaces of foliage causing yellowing, leaf fall, and twig and branch dieback. Serious infestations can cause plant death.

Rose scale (Order Hemiptera : Family Coccoidea) Aulacaspis rosae – Mainly found on the stems and branches of the plant, lack of control will allow the pest to spread to flower stalks and petioles. At this point the plant would be stunted, spindly and with a white, flaky crust of scales on the bark. Female Aulacaspis rosae may live for 1 year and may lay 80 eggs each with several overlapping generations living within milliimetres of the original parent.

• Leaf Cutting Bee (Order Hymenoptera : Family Megachilidae) Megachile spp. – Leafcutter bees are 6-16mm long and mostly black with bands of light-coloured hair. They chew pieces from the edges of leaves. The pieces are regular in shape, circular or oval. Damage is not often significant.

• Nematodes (Eelworms)(Order Tylenchida: Family Heteroderidae)

Root-knot nematode Meloidogyne spp.

See - Root-knot nematode - symptoms of Meloidogyne infestation in roses is stunting, slow-growth, pale green leaves and wilting in mild weather.

• Rose chafer (Order Coleoptera : Family Scarabaeidae) Macrodactylus subspinosus – The rose chafer is common to North America, and emerges in late May to mid June. These beetles form aggregations and feed upon foliage, buds, flowers, and fruit of roses and other ornamentals.

• Metallic flea-beetles (Order Coleoptera: Family Chrysomelidae) Altica spp. – The small, shiny and metallic Altica beetles have thickened hindlegs adapted to jumping, similar to fleas. The insects are 3mm long and chew holes of irregular shapes in young leaves and buds. As the leaves enlarge so do the holes.