With the risk of Barley Yellow Dwarf Virus (BYDV) in winter cereals nearly over, attention turns to spring cereals and the warm start to 2017 has encouraged early migration of aphids, especially in the North and West.
While in the South East, autumn infection tends to be more prominent, weather in the North and the West generally favours aphid survival going into the spring. Therefore applying an insecticide in May or June, can reduce BYDV infection in those areas, according to ADAS.
Where wet weather delayed sowing of spring cereals, resulting crops are most at risk from infection, with some crops already displaying signs of the virus.
Agrovista agronomist, Steven Gate says that while most spring barley has not yet emerged in North West England, he expects BYDV incidence to be high.
“Spring crops have gone in late this year, with most barley crops not going in until late-March, early-April, because soil conditions just didn’t allow.
“If we look back to last year, there was also a lot of April-drilled spring cereals, and as a result, there was barely a crop in the area that wasn’t infected. Lots of crops didn’t reach their full potential and I suspect this year could be similar,” he adds.
While there is no official threshold for BYDV control in spring crops, ADAS advise applying an insecticide where aphids can be ‘easily found.’
Unlike the autumn, there is no end to aphid migration in the spring, so timing the application of sprays can be difficult. Although once crops exceed GS31, there is no further economic benefit from treatment, says ADAS.
See also: Hot weather increases risk of BYDV
Where crops are infested at an early growth stage, the potential for BYDV to affect yield is greatest, and these crops are likely to benefit from pyrethroid treatment.
“Products should be applied when crops have 2 to 3 leaves, which is when aphids first begin to attack the plant.
“I would recommend applying a lambda-cyhalothrin pyrethroid spray where aphids can be easily found, which could coincide with early weed control sprays,” says Mr Gate.
Since grain aphids have moderate resistance to pyrethroids, growers are advised to use the recommended full field dose rate and should switch to an alternative mode of action if control is insufficient.