Using pyrethroids could help in controlling aphids that spread BYDV once neonicotinoid seed treatments can no longer be used. However, there are challenges when using this method of control.
Speaking at Bayer’s Speaker’s corner at Cereals, Dr Steve Foster of Rothamsted Research said three species of aphid potentially carry BYDV – grain aphid, bird cherry oat aphid and rose-grain aphid.
“Grain aphid shows resistance to pyrethroids but not the other two. Grain aphid is just on the edge of field rate so don’t reduce field rate. Some take it to 60 per cent but this is opening the door to allowing resistance to become greater.”
Loss of neonicotinoids will increase selection pressure for resistance to pyrethroids, he added.
In terms of cultural control, sowing cereals later can reduce the risk from aphids and BYDV, said Dr Foster.
Syngenta head of technical David King also advocated later sowing. “September and early October are the most susceptible time for aphids and BYDV. The problem with drilling later is you are more susceptible to the vagaries of the weather.”
Sowing in spring almost completely avoids BYDV infection, says Dr Foster. “But yields are much less.”
“Another solution is BYDV-resistant or tolerant varieties and some are in the pipeline.”
With suppliers only having until September 19 this year to treat seed with neonicotinoids, it is by no means safe to assume sufficient will be available this autumn, said Mr King. “If harvest is delayed, growers and agronomists should think about implementing a strategy for this season. Don’t assume all seed will be treated.”