Why Are There Aphids Clustered on My Beetroot Leaves?

Aphids found on beetroot are most commonly the black bean aphid (Aphis fabae) or the peach-potato aphid (Myzus persicae), which also infests many other vegetable crops. Both species colonise the underside of young beetroot leaves and on growing tips, extracting sap and causing leaves to curl, pucker, and distort around the colony. The more serious concern is that both species are efficient vectors of beet viruses (including beet yellows virus and beet mosaic virus), which can cause significant plant deterioration and reduced root development if infection occurs early in the season.

Identifying aphids on beetroot

Turn young beetroot leaves over and look at the underside — aphids are found most densely on the youngest, tenderest growth near the growing centre of the plant. Black bean aphids are densely black and form compact, heaving colonies. Peach-potato aphids are soft-bodied, green to yellow-green, and tend to be more dispersed. Both leave honeydew (sticky residue) on the leaf surface. Heavily infested young leaves curl tightly around the colony, hiding it from above-level inspection.

Physical control

Crush colonies on individual leaves by squeezing the leaf between finger and thumb, or rub off with a damp cloth. A jet of water from a hose effectively dislodges aphids from the flat, accessible beetroot leaves. Encouraging natural predators — ladybirds, lacewing larvae, hoverfly larvae — by avoiding broad-spectrum pesticides and growing insect-attracting flowers nearby keeps aphid populations regulated naturally through the season.

Beet virus — the real concern

Beet yellows virus (BYV) and beet mosaic virus (BtMV) are both transmitted by aphids feeding on infected plants and then moving to healthy ones. Infected plants show bright yellow or mosaic leaves and stunted growth, and the roots develop poorly. Once infected, plants cannot be cured — remove and bin severely affected plants. The best preventive is controlling aphid populations early in the season before they build up and move between plants.