Q What should I know about aphids on roses?
A Aphids are usually wingless and 1mm to 3mm long. They’re often called greenfly, though they can be other colours. At least seven species of aphid attack roses. The most troublesome is the rose aphid (Macrosyphon rosae), which can be dark-green or pinky-brown.
In small numbers they do little harm, but they can occur in large masses on shoot tips and suck sap from the vulnerable young growth. This deprives the developing shoot of water and nutrients, so buds fail to open and foliage is distorted.
Caption: Squashing aphids is one of the simplest methods of controlling them
Q How do I control aphids on roses?
A The simplest way to kill aphids is to squash them when you find them. Ladybirds and their larvae, as well as lacewing larvae and hover-fly larvae, feed voraciously on aphids, so encouraging these into the garden will help, too. Small birds, especially blue tits, also eat large numbers.
If you need to spray, try Bayer Natria Bug Control or Westland Resolva. All these insecticides will only kill insects they actually contact, and organic ones break down quickly, so repeat spraying will be needed.
Even organic insecticides will harm beneficial insects, however, so remove ladybirds etc first, and spray after dusk to avoid harming bees. Clusters of shiny black overwintering aphid eggs can be scraped off stems or pruned out.
Caption: Spray roses for aphids after dusk to avoid harming bees