Symptoms

Aphids cause direct damage as a result of their feeding activities and indirect damage as a result of their major role in the dissemination of numerous potato viruses.

The direct damage of aphids is caused by plant sap sucking and subsequently by the presence of sooty black mould, which develops on the honey dew rejected by the insects. Significative losses are related to large infestations of aphids in the crop over a long period. In this case, losses of 5 to 16 tonnes per hectare have been observed in long-cycle cultivars.

The indirect damage is caused by the dissemination of potato viruses, whose transmission to other plants can be done either in a non-persistent mode (the complete transmission process from one plant to another takes a very short time) as for the viruses PVY, PVA, PVS or PVM or in a persistent mode (the process takes a few hours or days) as it is the case for PLRV.

M. persicæ is the main and most efficient vector of the Potato virus Y (PVY) and the Potato leaf roll virus (PLRV). It is also often responsible for the dissemination of PVA, PVM and PVS.

However, less efficient vector species can be responsible for significant virus transmission when present in large numbers.