by Arable Farming July 2020
Control of BYDV without insecticides is set to become a reality as the first winter wheat variety with genetic resistance to the disease is launched. Teresa Rush reports.
As growers approach the second autumn drilling season since the loss of neonicotinoid seed treatment Deter (clothianidin), managing the barley yellow dwarf virus (BYDV) threat is sure to be among the crop protection challenges at front of mind.
So the progress of RGT Wolverine through the AHDB Recommended List process will be under close scrutiny in the coming months. Wolverine is the first winter wheat variety with genetic resistance to BYDV to be marketed in the UK.
A hard Group 4, Wolverine is currently a candidate variety for addition to the Recommended List for 2021/2022 and, as it has advanced through National List
and Recommended List trials, breeder RAGT has been working to develop advice for growers and agronomists as to how it can be best managed on-farm.
This approach has this season included a series of trials at the company’s UK headquarters at Ickleton, Cambridge, designed to assess the performance of
Wolverine in terms of yield and quality under high BYDV pressure across a range of drilling dates, with and without an insecticide treatment.
RAGT cereal and OSR product manager Tom Dummett explains: “The trial features an early sowing [beginning September], a normal sowing [beginning October] and a late sowing [early November]. The plots were infected with aphids carrying the PAV BYDV strain [the most common BYDV strain present in the UK] multiple times, every two weeks during autumn and then again into spring.
“We split the trial in half, so half is completely untreated and half has had a single insecticide spray and we used a decision support tool to identify the optimum time for spraying.”
In addition to Wolverine, the trial includes a further 14 varieties, some of which are current Recommended List lines and four are RAGT development lines containing the same Bdv2 resistance gene as Wolverine.
“The follow-on lines are at NL-1, so potentially will be entering National List trials this coming autumn. They have Santiago and Skyfall backgrounds and some have potential quality,” adds Mr Dummett.
While there has been less BYDV pressure this season compared Both decision support systems, which are being validated through tramline trials and field surveys, are based on previous work but they are being updated to include new factors, such as BYDV-tolerant varieties and the proportion of aphids carrying the virus.
“We’ve had our first BYDV season in the project without seed treatments. BYDV aphid incidence was very low in the field monitoring which we did in autumn and winter at about 40 sites.
“This is probably because of heavy rain over much of that period, which delayed or prevented drilling.”
Delayed drilling reduces the disease risk because it means crops emerge after aphid migration is over.
“It’s also likely that the rain washed off any BYDV vectors that did arrive in crops.”
The 2019/2020 winter was also very mild, Dr White says. Such conditions are usually associated with higher BYDV risk because they can extend the aphid
migration window and increase their secondary in-field spread.
“We would normally expect these conditions to increase BYDV infection levels in crops, but infections this spring appear to be low.
“Overall, it seems the winter deluge had a greater impact on the vectors than the mild temperatures.”