Following last autumn’s unprecedented levels of BYDV (barley yellow dwarf virus) pressure which caused winter wheat yields to fall by as much as 3t/ha, there is no reason to expect the issue to be less of a concern this season. Cereal growers are therefore urged to adopt a simple series of integrated pest management protocols to ensure this autumn’s crops are adequately protected from the imminent threat.

“After the UK’s hottest summer on record, there is no guarantee that temperatures will drop low enough this winter to sufficiently diminish what could otherwise be a very significant aphid population,” explains Rob Adamson, Head of Technical Development at ProCam.

 “Cereal growers must therefore use a combination of delayed drilling, variety selection, suitable pesticides and cultural controls to ensure the impact of aphid-borne BYDV virus on this year’s crops is kept in check.”

 Early drilled crops, especially those which emerge in September and the first half of October, will be at the highest risk of BYDV infection by virus-carrying midges, Rob explains. “Data from previous seasons shows that the risk of infection only reduces significantly in crops which emerge after mid-October. However, if conditions remain warm beyond this timing, even the latest emerging crops could still be vulnerable to infection.

 “We might not be able to control the climate, but we can control how and when crops are drilled. We’re therefore urging growers to consider their time of sowing and, where possible, to delay drilling until as late as possible, especially in those areas where crops have been impacted by BYDV in the past.”

 Rob also urges growers to remove the infection pathway for early post-emergence virus pressure from one cropping cycle to the next by eliminating any green bridges from the previous crop.

 “Early season infection can occur when the BYDV virus is transmitted by wingless aphids from volunteers and grass weeds in the previous crop to the newly emerging crop,” Rob explains. “The first point of control is therefore to remove the food source and habitat for these aphids by ensuring all cereal and grass plants are destroyed prior to the next crop being drilled. The highest risk will occur where crops are drilled into green cover, so it’s important to leave a sufficient gap – ideally five weeks – between the removal of volunteers and drilling the next crop.”

 In terms of variety selection, Rob warns that simply choosing the highest yielding variety from the Recommended List (RL) won’t always translate to the best results at harvest.

 “Historically, the RL hasn’t used data from plots infected by BYDV during the trials period,” Rob explains. “As such, the RL doesn’t always reflect how a particular variety will perform when stressed by the BYDV virus in real world conditions. However, with the arrival of tolerance and resistance traits in wheat varieties such as RGT Goldfinch and hybrid barleys like SY Kestrel, growers can now use genetic tools to combat the virus.”

 To determine how effectively these genetic traits can protect against BYDV, ProCam has compared the performance of 10 winter wheat varieties in the presence of the virus.

 “The yield responses of the varieties tested were quite dramatic,” Rob explains, “with varieties with proven genetic resistance such as RGT Goldfinch, Griffin, Gorgon and Guardsman all outperforming standard, non-resistant varieties.”

 The ProCam trial showed that the rate of BYDV infection was consistently and significantly below 10% in resistant varieties but ranged in severity from more than 30% to almost 50% in non-resistant varieties.

 “This translated into significant yield differences,” Rob continues. “In the presence of the BYDV virus, the resistant varieties outperformed some of the most popular varieties from the RL including Champion, Extase, Skyfall, Bamford and Solitaire. For example, while Champion only managed to yield a little over 7t/ha in the insecticide-free trial, RGT Gorgon and RGT Guardsman yielded just under and just over 10t/ha respectively.

 “With the latest and greatest varieties stealing the Recommend List’s headlines thanks to their higher yield potential in ‘ideal’ conditions, the promise they deliver doesn’t always translate into field performance,” Rob adds. “Growers in known BYDV hotspots should therefore think carefully about which variety will perform best in their specific circumstances.

 “Similarly, growers should embrace tools such as the AHDB’s new BYDV decision support tool to inform them when crops are most at risk from the next influx of aphids and to spray accordingly. And, when selecting which insecticide to apply, growers should consider Gocha (25 g/L esfenvalerate) as it is less harmful than other pyrethroids to beneficial insects such as ladybirds which naturally prey on aphids.”