A ‘HIGH RISK’ notice has been placed on barley yellow dwarf virus occurring in cereal crops across the country.

Infection this autumn follows a mild season which has resulted in considerable winged aphid activity and widespread reports of infection in spring crops across northern and western regions.

Hutchinsons’ northern regional technical manager, Cam Murray, told The SF that pressure in western Scotland had been ‘excessive’ as a result of large flights of aphids through spring. Classic yellowing symptoms had been found in spring oats, barley and wheat.

“Early-sown winter barley crops will be at particularly high risk this autumn,” he said. “Aphids are around, so growers have got to be vigilant and control any green bridge with cultivations or by spraying off with glyphosate.

“Cereal volunteers are the main food source for aphids, but any new green plant growth can help them colonise,” he pointed out.

The two key species responsible for its transmission are the grain aphid and bird cherry-oat aphid. There is also a strong case for seed treatment and the most effective way to protect early growth is to use a clothianidin-based seed treatment (as in Deter), said his Hutchinsons colleague, technical director, Dave Ellerton.

“I’d do this as routine for any early-sown winter crops this year. Deter typically provides six to eight weeks protection, after which time a follow-up pyrethroid can be applied if required, depending on weather and aphid activity.”

Although seed treatment might be seen as an additional expense compared with just a pyrethroid, it is worthwhile, especially in areas where other crop harvests increase autumn workloads, making it tricky to spray.

However, the duration of protection afforded by Deter reduced when sowing at lower seed rates, as less total active ingredient is applied. For example, reducing seed rates from 180kg/ha to 120kg/ha typically results in two weeks less persistence, which must be considered when timing follow-up treatments, said the expert.

Hot tips for managing BYDV:

Delay sowing autumn crops to emerge after main aphid migration.

Use a clothianidin seed treatment as baseline protection in winter crops.

Follow up with pyrethroid if required.

Monitor aphid pressure closely – see https://cereals.ahdb.org.uk/monitoring/aphid-news/aphid-monitoring.aspx

Remove any ‘green bridge’ for aphids, such as grassweeds or volunteers.

Drill spring crops earlier to outgrow any damage from spring aphid migration.

Consider beetle banks to increase natural predators (e.g ground beetles, parasitoids and spiders).