BYDV Assist


Following the loss of neonicotinoid seed treatments in cereals, autumn crops will be at higher risk of Barley yellow dwarf virus (BYDV) infection from aphids. An integrated pest management approach should be taken to reduce the risk, as well as regularly scouting fields for aphid presence which indicates risk of primary infection. Use the BYDV Assist tool to optimise spray timing to target the second generation of aphids, based on a model using the T-sum 170 day degrees (DD) threshold.

Primary infection occurs when winged aphids land on single plants and transfer virus, secondary spread is when the population of wingless aphids build up sufficiently to initiate aphid spread from the original infection point causing larger area of infection. Controlling larger areas of infection from secondary or even tertiary spread (occurs when the second generation spreads further to cause full field infection) will be key this autumn at reducing the impact of BYDV in cereal crops.

BYDV Assist is a scouting app designed to aid in decision making, in-field observations are still required.

Syngenta BYDV yellow water trap locations in the UK

Latest information from our yellow water traps

We are regularly monitoring aphid numbers in yellow water traps located at our Innovation Centres across the country, as well as the virus levels found in those samples.

-Suffolk coast

BYDV Assist - how it works

1. Add your field by pressing the + icon in the bottom right corner.

2. Input your location, BYDV Assist uses a 4 km accurate weather model.

3. Select your drilling and emergence date, this is when the 170 Day Degrees (DD) is calculated from.

4. If a foliar insecticide treatment has been applied input the date treated. This will reset the calculation to 0DD for 1 week.

5. A notification is given at 145DD to allow a couple of days to inspect the field and another when the 170DD threshold is reached.

6. If aphids are present when the 170DD is imminent or occurring an application spray is recommended.

7. The included spray application guide can be used to plan optimum application timings, once treatment is warranted.

How to use BYDV Assist App version 2.0
Bird cherry aphid

BYDV Facts

• Barley yellow dwarf virus (BYDV) is a persistent virus that will be carried by an infected aphid all its life.
• The main vectors for BYDV are Bird Cherry-Oat and Grain aphids.
• Once aphids have the virus they will be able to transmit it for the remainder of their lives.
• Plant infection will occur after ~30 minutes of aphid feeding.
• Only one infected aphid needs to feed to infect a plant.
• The earlier the infection the worse the impact on yield.
• Warm autumns will aid aphid population build up and spread.

BYDV - how should it be managed?

Cultural controls

  • Remove the green bridge.
  • Direct drill to increase beneficial predators.
  • Drill late to avoid the majority of aphid migrations.
  • Use higher seed rate to increase plant compensation and reduce spread.
  • Use the T-sum to calculate secondary and tertiary spread.


  • Bird Cherry-Oat aphids and Rose-Grain aphids have recently been showing some level of pyrethroid resistance, however the mechanism and how common this is in a population is still unknown.
  • Grain aphid KDR resistance appears to be fixed as heterozygous in the population, allowing partial to good control at full rates.
  • To ensure control, full label rates are needed. This reduces the likelihood of resistance becoming more widespread.