What are rose aphids?
Aphids, also known as greenfly and blackfly, are sap-sucking insects. There are several species that occur on roses in Britain.
Squashing aphids with finger and thumb is feasible on small roses. Aphids are eaten by ladybirds and their larvae, hoverfly larvae, lacewing larvae and are also killed by several species of parasitic wasps. Unfortunately these beneficial insects are often not present in sufficient numbers to prevent damaging aphid infestations developing.
Look for aphids on the shoot tips and underside of leaves from spring onwards. When seen, spray the plants with thiacloprid (Bayer Provado Ultimate Bug Killer, Bayer Multirose Bug Killer), acetamiprid (Scotts Bug Clear Ultra, Scotts Rose Clear for Bugs), thiamethoxam* (Westland Plant Rescue Bug Killer Ornamental Plants) or deltamethrin (Bayer Sprayday Greenfly Killer). If spraying is required while roses are in flower, do so at dusk when bees are not active.
Organic pesticides, such as pyrethrum (Py Spray Garden Insect Killer, Doff All in One Bug Spray), plant oils (Vitax Organic 2 in 1 Pest & Disease Control, Growing Success Shrub & Flower Bug Killer) or fatty acids (Bayer Organic Pest Control, Doff Greenfly and Blackfly Killer, Scotts Rose Clear Gun) are less harmful to ladybirds and other aphid predators but may need more frequent use because of their short persistence.
* Please note this product is being withdrawn. The withdrawal (in effect a ban) comes into force on 30 September 2013, but there is to be a period of grace to use up these materials by 30 November 2013. After this time it will be illegal to use them, any remaining products should be taken to a manned local authority household waste site where they should be handed over to the staff. For information on waste disposal sites see www.pesticidedisposal.org. It remains legal to use other neonicotinoid-based products that are not affected by the withdrawal. This withdrawal follows concern over their effects on bees.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
Aphids usually overwinter on roses as eggs laid on the stems in the previous autumn. However, in sheltered places they may remain active all year round.
Aphid numbers start to increase in spring when roses are producing new growth and reach a peak in early summer. Some rose aphids are green but a common species, Macrosiphum rosae, is pink. During spring and summer, the aphids are mostly wingless forms, 2-4mm long, that give birth to live young.
Winged forms develop when plants are heavily infested and aphids need to migrate to new host plants.