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 AHDB (Potatoes) 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.
The predicted early start to the aphid flight season due to mild winter temperatures was observed. 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 18 August is 7315. This figure ranks 6th of the last 10 years.
The total of 7315 aphids includes 2052 Rose-Grain aphids (Metopolophium dirhodum), 1501 Grain aphids (Sitobion avenae) and 2438 Bird Cherry-Oat aphids (Rhopalosiphum padi) making up 28%, 21% and 33% respectively of the total aphid vectors caught. 28% of the total number of aphids have been caught in the Edinburgh trap and 72% at Dundee. The summer migration of cereal aphids has now passed for all species.
The cumulative aphid vector pressure for 2019 (up to 18 August) at Edinburgh now ranks 23rd over the last 32 years. The Willow-Carrot aphid (Cavariella aegopodii) is responsible for 18% of the accumulated pressure, with the Rose-Grain aphid (Metopolophium dirhodum) at 18% and the Grain aphid (Sitobion avenae) accounting for 20%. The Bird Cherry-Oat aphid (Rhopalosiphum padi) now accounts for 31% of the accumulated pressure.
The cumulative aphid vector pressure for 2019 (up to 18 August) at Dundee ranks 18th over the last 32 years. Cereal aphids are now responsible for the majority of the accumulated pressure with the Grain aphid (Sitobion avenae) accounting for 31%, the Rose-Grain aphid (Metopolophium dirhodum) 20%, and the Bird Cherry-Oat aphid (Rhopalosiphum padi) accounting for 31%.