Minimising the Risk of BYDV – Farmers Guardian

The challenge from barley yellow dwarf virus was thought to be largely negated until, in autumn 2020, pressure from the disease brought it back into sharp focus.

 

Consider the impact of drilling date

Barley Yellow Dwarf Virus (BYDV) is a threat growers still face and is not to be neglected. And while the actual risk this season is unknown, there are several factors that can be taken into account to help determine risk.

Neil Watson, Hutchinsons technical manager, says: “The potential source of infection in the previous crop is a key factor. Generally, there was less BYDV showing last season, despite some late infections in winter crops and infection in spring crops that is notoriously difficult to control due to the prolonged period of flight into crops.”

Secondly, consider the green bridge effect from volunteers, he adds.

“Seed size in the harvested crop was good, so a smaller proportion of volunteers would be considered. Currently in mid-September, the soils are incredibly dry, making it less conducive to the germination of volunteers.”

However, it is still important to follow best advice and remove green stubbles as a primary source of infection.

“Either spraying off, or cultivation of volunteers at least five weeks before drilling will help reduce the survival and early ingress of aphids into newly-drilled crops.”

Also consider the impact of drilling date as the earlier the crop is drilled, the increased window of exposure an autumn crop will face, and also the greater number of potential sprays needed, Mr Watson says.

 

Infection

He points out that a mild winter has the same effect of prolonging the window of vulnerability at the other end of the season.

“Aphid flight into crops still occurs beyond 11^oC air temperatures. Winter temperatures also impact aphid survival and the potential for late primary or even secondary infection.

“Since the demise of the neonicotinoid seed dressings, it is increasingly probable we will see some BYDV in our crops from now on due to timing issues, the relatively short persistency of the products we now rely upon and more open warmer autumns and winters.”

Also not to be underestimated is the potential number of aphids carrying virus, in some cases upwards of 30%, considerably higher than the 5% historically considered the norm.

“To mitigate risk, control the green bridge and delay drilling where possible,” Mr Watson adds. He also believes tolerant varieties have a role to play.

“In wheat, presently there is only RGT Wolverine which has claimed resistance, although more options will be available in future.

“In barley, KWS Feeris is the only variety presently on the AHDB Recommended List that offers tolerance to BYDV, although others are available. In France, just about all the new six-row varieties have tolerance, the very first of the two rows was available last season.”

However, it is important to remember that genetic tolerance will not alleviate a need for a contact insecticide.

“It just means if timings become compromised, the impact on yield would not be as great. Reducing crop stress will also minimise the impact of BYDV as crop yellowing seems to attract aphids into the crop,” he adds.

It is therefore important to try to limit crop stress, particularly anything which might increase crop yellowing – whether that means maintaining adequate supply of micronutrients, or minimising crop damage from herbicide stacks.

“It is also important to aim for more targeted product application timings,” says Mr Watson.

“There are several tools that allow users to do this. Hutchinsons Omnia digital farming software provides a BYDV risk tool, combining 1km accurate weather data with the drilling date of the crop to give a field-by-field risk level and indicate the timing. This highlights the risk, enabling more targeted monitoring to then decide any action needed.

“Last but by no means least, when BYDV sprays are required – do not delay application just to suit other product applications to the crop.”