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. Sticky honeydew can cause subsequent growth of black Sooty Mould, especially under damp conditions. Not a major pest of swede.
Aphids are not a major pest of swede.
There is no product registered to control aphids on swede.
Cultural control: Encourage birds into the garden to feed on the aphids ie Blue Tits.