An estimate of the likelihood that aphids will transmit non-persistent potato viruses (e.g. PVY) in the field can be made using the data collected by the aphid suction traps. This estimate, the aphid vector pressure, is calculated by summing the total catch of each aphid species, after multiplication by a factor estimating the efficiency of that species as a vector of PVY. The vector pressure is a very coarse measure of the likelihood of virus transmission. Numerous factors will influence virus transmission, including complex interactions between aphid species and the strain of virus they transmit.

The 2008-2009 winter was actually slightly warmer than the average over the last 40 years. However, relative to recent winters it was fairly cool and as such the aphids were initially quite late to enter our suction traps. The weather over late June and early July was very favourable for the aphids this year. Two species of cereal aphids which are known to vector Potato Virus Y (PVY) the Rose-Grain aphid (Metopolophium dirhodum) and the Bird-Cherry Oat aphid (Rhopalosiphum padi) were flying in exceptionally high numbers in early July and have had a dramatic effect on the vector pressure as a measure of risk of transmission of PVY.  These two species were particularly abundant in the Dundee and Edinburgh trap catches. The Peach-Potato aphid (Myzus persicae) presented a more significant risk in the area around the Elgin suction trap. The aphid numbers from late July onwards have been low but, due to the large cereal aphid flights in June and early July, the virus vector pressures from all of the traps remained relatively high at all of the sites.