Spring barley growers will need to be alert to the risk of barley yellow dwarf virus (BYDV) this season as high levels of green bridge infection in autumn-sown crops are already being reported.

That means there is a widespread inoculum source for disease spread by aphid virus vectors this spring, plus climatic conditions for the past two seasons have been highly conducive for BYDV infection in spring barley, according to Syngenta's insecticides specialist, Max Newbert.

Despite some short periods of frosty weather over this winter, temperatures have been above average this season. “It is likely that some populations of bird cherry aphid, the primary vector of BYDV, will have survived,” he reported.

Any frosts, though, could have effectively hit insecticide resistant populations of grain aphid which can also spread infection: “There is strong evidence that genetic resistance to pyrethroids has made those aphids less fit to cope with cold weather. Furthermore, these resistant aphids typically only reproduce asexually, so we are less likely to see recombination and immediate build-up of resistant populations.”

He said Syngenta's Hallmark Zeon would be part of any control strategy, with full rate applications an essential part of minimising risk of pyrethroid resistant aphid populations developing. “For spring and early summer treatments, Hallmark Zeon has the important benefit of UV-protection, ensuring prolonged results even in sunny weather.”

Spring barley plantings are predicted to increase significantly this season – possibly reaching 800,000 ha as the area of autumn OSR has declined. With no insecticide seed treatments available, foliar protection of young plants is essential, he urged.

“Hitherto, it is later sown spring crops that have proven more susceptible to virus infection – when germination and early growth has coincided with aphid migration,” he pointed out. “But when early drilled crops are delayed by cold or dry weather, plants can remain at the most vulnerable early growth stages and subjected to disease transmission by infected aphids for longer.”