How to monitor and control the currant–lettuce aphid

The currant–lettuce aphid is the most important foliage aphid on lettuce and even small numbers can contaminate plants and affect marketability. This species does not normally transmit Lettuce mosaic virus.

• These aphids prefer to feed in the centre of the plant and can be extremely difficult to control once the lettuce plant has hearted

Scientific name: Nasonovia ribisnigri

Wingless adults are 1–3 mm long and green–to–yellow or pink in colour. They have a shiny abdomen with a dark green-to-black pattern on the upper surface. The two long tubes (siphunculi) at the rear end are pale with dark tips.

Winged adults have black siphunculi and antennae and a clear black pattern on the abdomen.

Dec–Feb: The aphid usually overwinters as an egg on currant or gooseberry bushes.

Mar–Apr: Eggs hatch and colonies form on the tops of the young shoots.

May–Jun: Winged aphids migrate to lettuce and wild hosts.

Jul–Sep: Several generations occur on late summer/early autumn hosts.

Oct–Nov: Winged aphids migrate back to the winter hosts and lay eggs. In warm locations, the mobile stages can survive and slowly reproduce on wild hosts throughout the winter.

Non-chemical control

They prefer to feed in the centre of the plant, making control difficult. The mobile forms are attacked by several natural enemies, including ladybirds, hoverflies, and lacewings.

To date, biological control with natural enemies has not been evaluated comprehensively in the UK, but the efficacy of several biopesticides is being evaluated.

Some lettuce cultivars with complete resistance to currant–lettuce aphid have been available for several years. However, in recent years, some populations have overcome this form of resistance.

Monitoring

Crop inspection is the best way to monitor currant–lettuce aphids because they tend to be caught in low numbers in suction and water traps.

Thresholds

None established.

Insecticide resistance

Resistance to pirimicarb and pyrethroid insecticides was detected in some UK field populations some years ago. However, the resistance does not appear to have had a major effect on levels of control in the field.