Of all the aphids, the peach potato aphid (Myzus persicae subsp. persicae) is the most important vector of viral diseases. It can transmit at least 100 different viruses and is thus rightfully feared by many growers.
Nymphs and adults extract nutrients from the plant and disturb the balance of growth hormones. As a result, the plant’s growth is retarded giving rise to deformed leaves or, if the infestation occurs early enough in the season, the death of young plants. Retarded growth and defoliation reduce yield,
Plant sap is rich in sugars, but has a low protein content. Aphids therefore need to extract large quantities of sap to get sufficient protein. The excess sugar is secreted in the form of honeydew, making the crop and its fruit sticky. Black fungal moulds (Cladosporium spp.) grow on this honeydew, contaminating fruit and ornamental crops and rendering them unsuitable for market. At the same time, photosynthesis in the leaves is reduced, affecting production.
The aphid’s saliva can induce strong “allergic” reactions such as malformations of the growing tips.