The lettuce root aphid (Pemphigus bursarius) infests the roots of lettuce plants. Other crops such as chicory and endive can also be colonised. Wild host plants include dandelions and sow thistles. Lettuce root aphids overwinter as eggs on Lombardy and black poplar trees. The eggs hatch in March-April and the nymphs feed on developing petioles which enlarge to form galls. A further generation of aphids is produced in the galls and they lead to winged aphids which migrate to summer hosts in June-July over a 4-5 week period. The winged aphids produce young as soon as they arrive on the summer host and these infest the roots, producing several generations of wingless aphids. In the late summer winged aphids return to poplar trees where they complete a sexual cycle after which the females lay the overwintering eggs.

Susceptible crops are only at risk of new infestations of lettuce root aphid during the period of migration and the start of this migration can be identified using a day-degree forecast which is provided each year in the AHDB Pest Bulletin.

References

AHDB Project FV 435 Evaluating aphid control strategies on lettuce.

AHDB SCEPTREplus trial SP36 Evaluating treatments for control of lettuce root aphid on lettuce.

Collier, R.H., Davies, J., Roberts, M., Leatherland, M., Runham, S. & Blood-Smyth, J. (1994). Monitoring and forecasting the times of attack of the lettuce root aphid, Pemphigus bursarius L. Integrated Control in Field Vegetable Crops. IOBC/WPRS Bulletin 1994, 17 (8), 31-40.

Dunn, J.A. (1959). The biology of lettuce root aphid. Annals of Applied Biology 47(3), 475-491.

Dunn, J.A. (1959). The survival in soil of apterae of the lettuce root aphid, Pemphigus bursarius (L.). Annals of Applied Biology 47(4), 766-771.

Dunn, J.A. (1960). The natural enemies of the lettuce root aphid, Pemphigus bursarius (L.). Bulletin of entomological Research 51(2), 271-278.

Parker, W.E., Collier, R.H., Ellis, P.R., Mead, A., Chandler, D., Blood Smyth, J.A. and Tatchell, G.M. (2002). Matching control options to a pest complex: the integrated pest management of aphids in sequentially-planted crops of outdoor lettuce. Crop Protection, 21, 235-248.

Philips, S.W. et al. (1959). Escaping an ecological dead-end: asexual overwintering and morph determination in the lettuce root aphid Pemphigus bursarius L. Ecological Entomology 24(3), 336-344.

Web page on Pemphigus bursarius.