BYDV Assist app for iPhone and iPad

BYDV Assist is a scouting app designed to aid in spray timing to control Barley yellow dwarf virus (BYDV), which is primarily transmitted by the bird cherry–oat aphid and the grain aphid. As such
fields still need to be inspected for aphid pressure when considering foliar insecticides to control primary infection and secondary spread.

The app will not predict primary infection, this occurs when the initial aphids migrating into the crop colonising relatively few single plants in the crop. BYDV Assist calculates when the second
generation offspring are produced to the extent where they spread causing larger areas of infection, which are far more damaging. Controlling the secondary generations is key for robust BYDV management in autumn.

The timing of the second generation can be calculated by accumulating the daily average air temperatures above 3oC, below which aphids will not be clonally reproducing. On average it take 170 day degrees (DD) for enough second generation to be produced to cause localised areas of infection.

If two secondary events occur in a row (340DD) this would indicated tertiary spread, where the whole field will be infected with aphids, causing the highest risk of yield loss.

This tool can be used to calculate when the 170DD threshold has been reached at your location using our current weather data, as well as our historical data to help predict where it could occur.

To use the app:

· Input your location this will then pick the closest weather station.

· Select your emergence date (this is when the 170DD is calculated from).

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

· A warning is give at 145DD to allow a couple of days to inspect the field and another when the 170DD threshold is reached.

· If aphids are present and the 170DD is imminent or occurring a spray is recommended.