31 October 2024

BYDV control programmes and tolerant varieties

Many winter barley varieties are now rated highly for Barley Yellow Dwarf Virus (BYDV) tolerance, but does this mean they should be managed differently to other varieties?

To shed light on this and to discuss BYDV control strategies, ongoing research and the role of decision support tools, Dr Louise McNamara, an Entomologist at Teagasc Oak Park, joined Michael Hennessy on a recent episode of the Tillage Edge podcast.

Outlining the consequences of the viral disease caused by aphids, Dr McNamara explained: “BYDV can affect all cereal crops and it can cause significant yield losses when you have sufficient virus pressure. It can affect both the yield and the grain quality.”

Although disease pressure is contingent on a number of factors, including planting date, weather and field location – all factors affecting aphid movement, Dr McNamara highlighted a number of control strategies farmers need to be aware of for early-sown, October-sown and November-sown crops.

Early-sown crops

For early-sown crops, those sown in September, she noted that these would be considered medium to high risk for BYDV, adding: “These crops should benefit from a spray at the two to three leaf stage and a second spray in early November.”

Where the second application is missed, she noted that research has shown there could be a benefit to spraying up to January or February, depending on the viral pressure, but you don’t need more than two sprays.

“There is no benefit in spraying after growth stage 31. The crop can still go yellow if it gets infection after growth stage 31 but it will have no major impact on yield.”

October and November planted cereals

As the planting date moves later, the requirement for insecticide applications to control BYDV also diminish, with Dr McNamara adding: “For October-planted cereals, we would say that one application of insecticide is sufficient to protect yield.

“If you are planting in November and it’s emerging later, generally you wouldn’t need an insecticide. As we move into the winter and its gets colder, aphids are less active, they are flying less, so there is less of a risk of them getting into your crop.

“However, if you are in a high risk area, maybe beside the coast or if it was a very warm winter, the risk maybe higher but generally where crops are emerging in November, they don’t need an insecticide.”

When posed the question as to what control programmes farmers with tolerant varieties sown should follow, Dr McNamara said: “Tolerant varieties are an important tool and they are going to be a very important tool into the future.

“Early trial results do suggest that they are promising but, for now, we don’t have enough evidence yet to say whether they are sufficient on their own without a spray in high pressure years. For now, we would say treat them the same and apply an insecticide if it is recommended based on your planting date.”

Ongoing research at the Oak Park Crops Research Centre was also discussed, with Dr McNamara outlining decision support tools and how they may work in combination with tolerant varieties in the future. A decision support tool is now in its third year of testing at Oak Park on a plot and tramline scale study.

On the necessity of such decision support tools, Dr McNamara added: “In the future, we would like to see more information to help farmers make a more precise decision. It is not some much about knowing when to spray because we can estimate roughly when to spray and when to get a good benefit from spray, it is to work out the years you don’t need to spray, that’s what we want decision support tools for.”

For further insights on the best strategies for controlling BYDV in winter cereals, listen to the Tillage Edge podcast below: