Lettuce-root aphid - Plant Pests

Lettuce-root aphid belongs to the root aphids, small gray aphids that live on the roots of plants.

Also known as:
Woolly root aphid

recognize gall of Lettuce-root aphid — Gall of Lettuce-root aphid on Black Poplar, photo: Jean Claude - CC BY-SA 4.0

Lettuce-root aphid (Pemphigus bursarius) belongs to the root aphids, small gray aphids about 2.5 mm in size. These aphids live underground on plantroots. They form a white, stringy mass on the roots; a breeding ground for fungi. Root aphids slow down growth and the aphids can transmit diseases.
The aphids hibernate as eggs in the rough bark of Lombardy and Black poplar. After winter, the hatched viviparous aphids move to the leaves where they leave a gall on the leaf. One hundred to two hundred winged aphids are born in the gall. In the spring, these aphids fly to the host plants (Umbellifers: endive, lettuce, Belgian endive, carrots, prickly sow-thistle, common nipplewort) where they move to the roots during the summer.

Where to find

Endive
Lettuce
Belgian endive
Carrot
Black poplar (Populus nigra)
Lombardy poplar (Populus nigra Italica)

Control

Dispose of infested plants. Root aphids are difficult to control: they like to hide underground. If the aphids have moved from the poplars to the host plants in summer and have not yet descended to the roots, there is an opportunity for control with pyrethrum, Insecticidal soap, soapy water spray, rhubarb spray or nettle spray.

Prevention

Create an environment where natural enemies (ladybirds, earwigs, parasitoid wasps and lacewings) feel at home. Clean up leftover plant debris well; in mild winters root aphids can hibernate in these.