Spring barley growers will need to be alert to the risk of Barley yellow dwarf virus (BYDV) this season. With high levels of infection in autumn sown crops already reported, there is a widespread inoculum source for disease spread by aphid virus vectors this spring.
Climatic conditions for the past two seasons have been highly conducive for BYDV infection in spring barley, according to Syngenta Insecticides Technical Manager, Max Newbert.
“The cold slow start to growth in April resulted in small plants from early spring sowings, which were more susceptible to infection during prime aphid migration periods in May,” he warned.
Despite some short periods of frosty weather over this winter, overall temperatures have been above average, again, this season. “It is likely that some populations of Bird Cherry Aphid, the primary vector of BYDV, will have survived,” reported Max.
However, the good news is that the recent frosts could have effectively hit insecticide resistant populations of Grain Aphid that can also spread infection, he added.
“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.”
Max advocated that Hallmark Zeon would be the mainstay 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 in each droplet, ensuring prolonged results in sunny weather.”
Spring barley plantings are predicted to increase significantly this season; possibly reaching 800,000 hectares as the area of autumn OSR has declined. With no insecticide seed treatments available, foliar protection of young plants is essential, urged Max.
“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.”
Max reminded growers that whilst most autumn sown cereal crops were now sufficiently advanced to suffer limited impact from spring virus infection, there remained a significant area of late sown crops, from drilling delayed to allow blackgrass control, which could still be affected and should be monitored for aphid activity and control.