Virus Epidemiology

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. Details of the vector efficiencies used in these calculations are available via the Potato Council Aphid Monitoring webpages. 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.

In most years, the aphid vector pressure in Scotland is largely dependent upon the activity of cereal aphids, although peach-potato aphids and potato aphids may also be important.

2018 Summary

After a fairly slow start, flight activity of some species increased with the good weather in May. A second wave of activity, mainly from cereal aphids, was observed during July. The total number of aphids known to vector potato viruses that have been caught in the Dundee and Edinburgh suction traps up to the week ending 19 August is 17199.  This figure now ranks third of the last 10 years (behind 2009 and 2010).

The total of 17199 aphids includes 9246 Bird Cherry-Oat aphids (Rhopalosiphum padi) and 4537 Rose-Grain aphids (Metopolophium dirhodum) (making up 54% and 26% respectively of the total aphid vectors caught).  17% of the total number of aphids have been caught in the Edinburgh trap and 83% at Dundee.

Edinburgh 2018

The cumulative aphid vector pressure for 2018 (up to 19 August) now ranks 17th over the last 31 years.  The Bird Cherry-Oat aphid (Rhopalosiphum padi) accounts for 59% of the cumulative pressure, and the Grain aphid (Sitobion avenae) for 20%.

Dundee 2018

The cumulative aphid vector pressure for 2018 (up to 19 August) at Dundee ranks 10th over the last 31 years.  The Bird Cherry-Oat aphid (Rhopalosiphum padi) is responsible for 53% of this value and the Rose-Grain aphid (Metopolophium dirhodum) for 22%.