Posted: 24/04/2015 at 11:46
Do they have blackfly on at the moment Chris? Seems a bit early for them. If so try spraying with soapy water - a few drops of an 'eco' type washing-up liquid in a sprayer will do. If that doesn't shift them, see the RHS advice on which organic insecticides is safe for use on edible fruit trees:
"Pesticides based on natural compounds and/or with a physical mode of action:
These pesticides are contact in action and have short persistence, so thorough spray coverage, especially to the underside of leaves, is necessary. They can be used on ornamentals and edibles up to one day before harvest. Whilst good control can usually be gained of aphids feeding exposed on stems and leaves those protected by curled leaves are unlikely to be controlled. Products include: Pyrethrum (e.g. Py Garden Insect Killer, Bug Clear Gun for Fruit & Veg, Py Bug Killer Spray, Growing success Frit & veg Bug Killer, Growing Success Shrub & Flower Bug Killer and Pyrol Bug & Larvae Killer); Fatty acids (e.g. Bayer Organic Bug Free, Bayer Natria Bug Control, Doff Greenfly and Blackfly Killer, Doff Universal Bug Killer); Plant/fish oils (e.g. Vitax Organic Pest and Disease Control, Bug Clear for Fruit & Veg), Plant oil winter wash can be used to treat overwintering eggs on dormant deciduous fruit trees and bushes (e.g. Growing Success Winter Tree Wash or Vitax Winter Tree Wash); blend of surfactants and nutrients (e.g. SB Plant Invigorator)."