Introduction

Aphids can cause significant yield reductions in potatoes in New Zealand as a result of direct feeding and virus transmission. Several viruses are transmitted to potato crops by aphids. These include potato viruses Y (PVY), M (PVM) A (PVA), S (PVS) and X (PVX), alfalfa mosaic virus (AMV), potato aucuba mosaic virus (PAMV), and potato leafroll virus (PLRV). Nine of the 28 aphid species that are actual or potential potato virus vectors are capable of transmitting PLVR. Of these, the green peach aphid (Myzus persicae) is considered the most important vector, and has developed resistance to a number of insecticides. Other aphids include the foxglove aphid (Aulacorthum solani), and the potato aphid (Macrosiphum euphorbiae). The melon aphid (Aphis gossypii) also colonises potatoes, and is a vector of several potato viruses other than PLRV.

Aphid flights often preceed the buildup of aphids in a potato crop, and therefore, monitoring of their occurrence is important in management of viral diseases. In Canterbury aphids that colonise potatoes have two peak flights, one in late spring and another in autumn, but the timing, magnitude and duration of the flights varies considerably between seasons and between years.The peak flights of aphids in other regions where potatoes are grown are not well understood at this stage.

An industry led project has been initiated to ensure that aphids in potato crops do not develop resistance to currently used insecticides. Resistance by aphids to insecticides that are commonly used in potato crops has already occurred. The project aims to develop cost effective management systems for control of aphids, and the viruses that they spread in potatoes. The influence of predators on aphid populations under different spray regimes is also being assessed. The research aims to determine the extent of aphid resistance to commonly used insecticide strategies, so that effective strategies to control aphids for the prevention of virus infection in potatoes can be developed.