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.
2011 Summary
A cold winter and the wet and windy spring of 2011 delayed the beginning of the season for many aphid species, however, the warm and wet summer heralded an increase in cereal aphids. The number of some species of cereal aphids linked to the transmission of PVY and associated viruses have now started to decline.
The number of Peach-potato aphids (Myzus persicae) caught in Scottish suction traps has returned to a lower level after an interesting peak last week. The total number caught to date remains close to average and the Peach-Potato aphid continues to be responsible for a small proportion of the cumulative virus pressure in both the Edinburgh (2%) and Dundee traps (2%). No Peach-Potato aphids were caught in SASA's field-based traps based at Edinburgh and Fife during 13-20th July.
After remaining below average for the early part of the season, cumulative vector pressures are now starting to rise at both Dundee and Edinburgh.
Edinburgh
The cumulative aphid vector pressure at Edinburgh on 24 July stands at 938, ranking eighth out of the previous twenty-eight years. The Bird-Cherry Oat aphid (R. padi) is responsible for 27% of this figure and the Rose-Grain aphid (M. dirhodum) now accounts for 62% of this value. No Peach-potato aphids (M. persicae) were caught in the trap during the week 18-24 July.
Dundee
The cumulative aphid vector pressure for Dundee as of 24 July has risen to 1013, ranking thirteenth out of the previous twenty-eight years. 46% of this value is due to the Bird-Cherry Oat aphid (R. padi) and the Rose-Grain aphid has increased at this site and now accounts for 50%. No Peach-Potato Aphids (M. persicae) were caught in the Dundee trap last week.
Elgin
The cumulative aphid vector pressure for Elgin as of 24 July stands at 230, ranking eleventh out of the previous twenty-six years. 21% of this value is due to the Leaf-Curling Plum aphid (B.helichrysi),the Bird-Cherry Oat aphid (R. padi) is responsible for 36% and the Rose-Grain aphid is also responsible for 36%.
SASA
