Barley yellow dwarf virus (BYDV) tool for cereals

Aphids can transmit barley/cereal yellow dwarf viruses (BYDV) to cereal crops. Decision support tools can indicate high-risk periods and guide management interventions.

Use decision support tools alongside local knowledge and risk attitudes to determine treatment requirements.

New BYDV tool

Based on decades of aphid biology science, virus epidemiology studies and computer modelling, the new tool considers many more risk factors than the T-sum tool.

It puts crop economics at its heart, so you can make informed sowing-date and risk-based spray decisions for BYDV-susceptible varieties.

BYDV tool launch: 12pm on Tuesday 18 August 2026.

First released in 2018, this tool predicts aphid development, rather than BYDV risk directly.

• Initially, aphids colonise relatively few crop plants
• The wingless second generation tends to move away from the plant originally colonised, which spreads the disease
• As a result, control is targeted at this generation

This T-sum tool calculates the accumulated daily air temperatures above a baseline temperature of 3ºC from the start date, which is either on the day of crop emergence or after a pyrethroid application.

The second generation may be in the crop when the accumulated temperature, shown by the blue line, reaches 170ºC.

When the shading changes from green to red, it indicates that the T-sum is above 150ºC, which is when frequent crop monitoring should start.

On the map, click on a site circle to see the corresponding T-sum data.

Click on the ‘Aphid flight activity’ button to see when temperatures fall under 11ºC, which is associated with limited aphid flights.

The tool activates each autumn on 1 September.

Further information