Introduction
From midsummer onwards, the catches of cereal aphids in the suction traps usually dominate the Scottish aphid bulletin and affect significantly the index that is used to estimate the vector pressure for aphid-transmitted potato viruses. Two species, the Rose-Grain aphid (Metopolophium dirhodum) and the Bird Cherry-Oat aphid (Rhopalosiphum padi), are known to be vectors of non-persistently transmitted potato viruses (e.g. PVY) and because they can occur in high numbers in the suction traps, each individual species can make a relatively high contribution to the overall aphid vector pressure index. SASA is currently conducting field trials on virus transmission to determine whether these contributions are appropriate when attributed to data from suction trap catches.
As would be expected, cereal aphids are also important pests of cereal crops, causing direct damage by feeding on crops and through the transmission of viruses such as barley yellow dwarf virus (BYDV).
Cereal aphids in 2009
From late June to mid July, two species of cereal aphids which are known to vector Potato Virus Y (PVY) were flying in exceptionally high numbers and have presented a very significant risk of transmission of PVY. These two species are the Rose-Grain aphid (Metopolophium dirhodum) and the Bird-Cherry Oat aphid (Rhopalosiphum padi). Both species were particularly particularly abundant in the catches of both the Dundee and Edinburgh suction traps, indicating that these phenomenal catches are not localised to just one trap site and are likely to be typical of eastern central Scotland.
Potato varieties that have been particularly prone to the acquisition of PVY in the classification scheme include King Edward, Harmony, Shepody, Maris Peer, Nicola.
From mid July the numbers of these cereal aphids declined to very low levels, however the autumn migrations of both the Bird-Cherry Oat aphid (Rhopalosiphum padi) and the Apple Grass aphid (Rhopalosiphum insertum) are now occuring as is expected for this time of year.
Rose-Grain aphid (at Elgin, Dundee and Edinburgh)
The total catch of 5940 Rose-Grain aphids (Metopolophium dirhodum) in the traps to 4 October ranks the fifth highest out of the last 26 seasons. Of these aphids 12% were caught at Elgin, 65% at Dundee and 23% at Edinburgh.
Grain aphid (at Elgin, Dundee and Edinburgh)
The total catch of 2767 Grain aphids (Sitobion avenae) to 4 October ranks eleventh highest out of the last 26 seasons. Of these aphids 24% were caught at Elgin, 50% at Dundee and 26% at Edinburgh.
Bird-Cherry Oat aphid (at Elgin, Dundee and Edinburgh)
The total catch of 20896 Bird-Cherry Oat aphids (Rhopalosiphum padi) to 4 October ranks eighth highest out of the last 26 seasons. Of these aphids 6% were caught at Elgin, 65% at Dundee and 29% at Edinburgh. As can be seen from the figure, the largest migration of this species typically occurs in the autumn and therefore does not usually present any serious risk to the virus health of potato crops. Large migrations occurring in early July present a much greater concern.
Apple-Grass aphid
The total catch of 8834 Apple-Grass aphids (Rhopalosiphum insertum) in the four Scottish traps to 4 October ranks thirteenth highest out of the last 26 seasons.
Cereal aphids in 2008
Cereal aphids in 2007
Cereal aphids in 2006
