Blackfly and greenfly (aphids) are very common sap sucking pests affecting nearly all types of plants. Colonies are visible around new buds or shoots in spring onwards. Leaves may twist or yellow and become puckered and distorted as they develop. Specific species of Aphids can be found on specific host plants.
Product solution: Provado Ultimate Bug killer - Ready to Use / Concentrate 2, Sprayday Greenfly Killer, Provado Ultimate Fruit and Vegetable Bug Killer - ready to use / concentrate.
For peppers and chillies grown in a greenhouse consider using Greenhouse Flycatchers wherever possible.
Cultural control: Encourage birds into the garden to feed on the aphids ie Blue Tits.