Sales of barley yellow dwarf virus (BYDV) tolerant winter barley varieties have reached exceptionally high levels over recent weeks.
But do claims relating to tolerance mean they should be managed differently, relative to traditional varieties?
Teagasc entomologist, Dr. Louise McNamara discussed this matter on a recent edition of the Tillage Edge podcast.
BYDV
Outlining the consequences of the viral disease caused by aphids, she explained:
“BYDV can affect all cereal crops and it can cause significant yield losses when sufficient virus pressure exists. It can affect both crop yield and the grain quality.”
Disease pressure is contingent on a number of issues, including planting date, weather and field location. These are all factors that 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, planted 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.
Dr. McNamara continued: “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.
McNamara continued: “For October-planted cereals, we would say that one application of insecticide is sufficient to protect yield.
“If planting in November and the crop is emerging later, generally there is no requirement for 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 a crop.
The Teagasc entomologist confirmed that BYDV tolerant cereal varieties are an important tool and they are going to be a very important tool into the future.
She said: “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 planting date.”