The AHDB has launched a new tool to help you reduce the impact of Barley yellow dwarf virus (BYDV) in winter wheat and winter barley.
The AHDB says the new tool is based on decades of aphid biology science, virus epidemiology studies and computer modelling and considers many more risk factors than the T-sum temperature tool. It also puts crop economics at its heart so that growers can make informed sowing-date and risk-based spray decisions
According to the AHDB’s Sacha White, the new tool is powered by a model trained on the bird cherry-oat aphid, which is now known to be the most significant BYDV vector across the UK in most situations, mainly due to the relatively high numbers that fly in the autumn.
Exceptions include crops sown very early or where there’s poor green-bridge management, where grain aphids can also be problematic.
The BYDV tool considers:
- Local temperatures, including historic, actual and forecast data for the next nine days
- The number of aphids flying (historic and actual)
- The proportion that carries the virus
- Local risk factors, such as surrounding land use
- The relationship between infection and yield and financial losses in susceptible varieties
The inclusion of bird cherry-oat data is a major advance over the T-sum tool, which assumes that virus-carrying aphids are present at crop emergence or after a spray.
“We get most of the aphid data from the GB Rothamsted Insect Survey suction-trap network, which covers England and Wales. We also get data from a suction trap in Northern Ireland, which is run by the Agri-Food and Biosciences Institute,” says Sacha.
According to the AHDB, BYDV has become more problematic in recent years for several reasons, including higher temperatures that favour aphid development and flights, the withdrawal of neonicotinoid seed treatments, SFI payments that reward no-insecticide use and pyrethroids slotted in with herbicides that target weeds rather than aphids
The BYDV tool also considers many other factors, including pyrethroid insecticide persistence and the diminishing returns associated with follow-up sprays.
To run an assessment, growers only need to enter a few details; these are:
- Field location
- Crop type
- Emergence or sowing date
- Whether the field is exclusively surrounded by arable land
The tool also uses default values for average UK cropping situations, which cover:
- Plant population density
- Expected yield and grain price
- Insecticide treatment cost
- Whether the farm is receiving SFI payments for not using insecticides
To tailor the results, the AHDB recommends replacing the defaults with actual field-specific values.
The tool’s spray assessment shows when the next spray decision is needed. Recommendations are based on the predicted economic threshold, which is when the cost associated with yield loss is likely to equal the treatment cost.
Predictions are strongest for autumn-applied sprays, especially the first spray. It also clearly indicates the urgency for decisions, including a ‘high urgency’ notification when a spray may need to be considered within a week.
The tool’s sow-date assessment reveals how BYDV risk could change when crops are drilled earlier or later than the farm’s standard target sowing date.
“We know that drilling relatively late can significantly reduce BYDV risks. The tool doesn’t currently account for BYDV resistance/tolerance, which is complex and diverse. However, such varieties are more forgiving when weather forces suboptimal or missed sprays,” adds Sacha. “Our research shows that using the tool, alongside local knowledge, can reduce the number of insecticide applications and protect more yield than the T-sum tool when BYDV is present.”
The AHDB has worked with farmers to help develop the tool with investment from BASF, KWS, Limagrain and Syngenta. For more information, please visit: https://ahdb.org.uk/bydv
