Cereal growers asked to help develop a new BYDV management tool

A powerful new BYDV management tool will arrive this autumn to give farmers greater control over aphids in winter cereals – and you can help us develop it. Sacha White (lead crop protection scientist) explains.

Barley yellow dwarf virus (BYDV) can cause major yield losses in winter cereals. It’s important to manage virus-spreading aphid vectors.

When neonicotinoid seed treatments were withdrawn in 2018, it set back aphid management by decades and saw a return to the routine use of foliar pyrethroid sprays in the autumn.

Although pyrethroids are relatively cheap, every spray puts pressure on non-target organisms and increases insecticide-resistance risks. This means they need to be used carefully.

Our current BYDV tool has been available for several years. It predicts the presence of the second aphid generation in crops, which is most associated with BYDV spread.

It only needs two inputs:

• A start date (usually crop emergence or spray date)
• Accumulated daily air temperatures (from the start date)

Although it's a simple and effective way to time sprays, it overlooks many nuances that influence virus-transmission risks.

To compensate, it’s conservative and tends to suggest more sprays than may be required to prevent unacceptable yield losses.

Following decades of advances in aphid biology science, virus epidemiology and computer modelling, a 12-month review of BYDV risk (2018–19) by the Game and Wildlife Conservation Trust identified the potential to develop a much better tool.

Based on the review’s recommendations, we funded ADAS in 2019 to develop a model to account for additional measures of risk and provide comprehensive information on BYDV.

Although bird cherry-oat aphid, rose-grain aphid and grain aphid all transmit BYDV, the ADAS work confirmed that the former aphid is by far the most significant virus vector across the UK, so we trained the model on this species.

Rose-grain aphid is rarely seen in winter crops (it overwinters on roses), and grain aphid flies in relatively low numbers in the autumn.

This has been confirmed by recent in-field monitoring work and results from the Rothamsted Insect Survey (RIS) suction-trap network (across England and Wales).

Although grain aphids can spread BYDV, this only happens in limited situations.

For example, high summer infestations use green bridges (e.g. grass weeds or cereal volunteers) to move to following cash crops. Early emerging crops (before mid-September) are affected the most.

We also now know grain aphid transmits BYDV less efficiently than bird cherry-oat aphid.

Suction trap data is representative of aphids flying over a radius of about 80 km, according to RIS.

ADAS found that the traps provide a good indication of aphid migration trends, crop infestations near traps (especially up to 10 km away) and the proportion of aphids carrying virus up to 40 km away.

The investment (skill, time and money) needed to locate and identify aphids (and determine if they carry BYDV) means that suction-trap results provide a very useful proxy for modelling in-field virus pressures.

What the new model includes

In addition to the number of aphids carrying BYDV, the new model considers many other data sources.

These include minimum, maximum and mean temperatures as well as crop-specific information such as:

• Cereal type
• Sowing date
• Plant populations
• Treatment costs
• Predicted yield
• Estimated grain price
• local risk factors

Initial validation work found the model accurately predicted BYDV risk, based on symptom development in untreated crops.

It also guided control as good as or better than the current BYDV tool in treated tramline and plot trials.

The best news is that it did this with fewer insecticide applications and provided yield benefits (where BYDV was present).

The tool only needs a few farm-specific inputs, as several data sources are embedded.

For example, it automatically uses five-year growing-season (1 September to 31 August) data sources. This includes local temperature patterns, as well as forecast temperature data for the next fortnight.

Based on our virus screens over several autumns, the model assumes about 20% of aphids carry virus.

This might seem low, but the virus isn’t passed from parent to nymph. New aphids need to feed on infected plants to take it up.

Farm-specific inputs include:

• Location information, which tells the tool where the nearest suction trap is and identifies other key area characteristics, such as proximity to the sea and other arable land
• Crop type (wheat or barley)
• Plant population
• Sow dates (or crop emergence
• Predicted grain yield and grain price

The tool crunches the data to show the daily risk level based on the estimated percentage of the crop infected with BYDV. It also:

• Indicates optimum spray timings
• Accounts for diminishing returns from follow-up sprays
• Considers pyrethroid insecticide persistence
• Runs cost-benefit analyses for every potential spray
• Factors in any loss of ‘no-insecticide’ payments

The tool also supports cultural control decisions ahead of drilling (such as field selection and drill date).

In high-risk situations, drilling crops after mid-September is particularly effective, as is opting for a variety with BYDV resistance or tolerance.

Due to the complexity and diversity of resistance/tolerance, the new tool does not yet account for it when determining treatments.

However, such varieties are more forgiving when weather forces sub-optimal spray timings.

Last year, we funded ADAS to finish the model and put it in a format suitable for a web-based app.

A small group of farmers is helping us finalise the tool, with two online user-group meetings later this month:

• 23 March 2026 (11:30am)
• 26 March 2026 (3:00pm)

If you would like to get involved, please contact me.

Our team will also be at several events this summer, where you can discuss the tool.