One of the three major fears of early planting is the risk of barley yellow dwarf virus (BYDV) infection; the other two being increased weed and disease problems. The withdrawal of neonicotinoid insecticides signalled a big challenge for a serious but intermittent disease, spread by aphids.

With an increasing requirement to decrease overall pesticide usage, it becomes more important to have justification for any application.

Any tool which increases the accuracy of the need for treatment is useful

Knowing that a pest has arrived, is about to come or is multiplying within a crop, provides a valuable guide to justify pesticide application.

Any tool which increases the accuracy of the need for treatment is useful. Last week, Syngenta launched a smartphone app to help optimise the control of aphid spread within a crop. This app, called BYDV Assist, is now available for smartphones.

Infection dynamics

BYDV infection begins with primary infection. This occurs when winged aphids land on single plants and transfer the virus. Secondary spread occurs when the population of wingless aphids builds up to sufficient numbers to initiate aphid spread from the original infection point, causing a larger area to be infected.

It is virtually impossible to prevent primary infection because it can happen over a prolonged period. And even if we know that aphids are flying, there is still uncertainty as to whether they are carrying the virus or not. The app cannot answer this question, but growers will need to protect their crops once they know there is an infection risk.

It is the multiplication that takes place on the plant, and then moves on to neighbouring plants, that begins to form the infected circle or patch

Preventing primary infection is not the major concern. It is the multiplication that takes place on the plant, and then moves on to neighbouring plants, that begins to form the infected circle or patch. This app targets the prevention of spread.

Controlling further spread from secondary or even tertiary spread, will be vital to reducing the impact of BYDV in cereal crops this autumn.

On your phone

BYDV Assist is simple to load and use. It forecasts the likely conditions that cause secondary spread, based on accumulated temperature post-emergence, which is one of the main drivers of aphid multiplication. Specifically, it uses the T-Sum model based on the accumulation of 170 day-degrees from crop emergence.

Once installed, you enter the details for each individual field, including its location.

While the app can help growers to optimise aphicide timings, it does not replace the need for crop inspections

The app does the rest. It gets local temperature readings – you input the sowing and emergence dates. Then you get a predicted spray date based on normal weather up to then. This date can change if the temperature in the interim is higher or lower than had been predicted.

While the app can help growers to optimise aphicide timings, it does not replace the need for crop inspections. Multiplication can only happen if aphids are present and the app cannot calculate that.

Adding more information in time

This is still a useful tool to guide grower decisions. However, it does not predict the primary infection or tell if invading aphids are carrying the virus. If they have no virus, the aphids carry no real threat.

However, when advice from Teagasc’s new aphid monitoring towers is available, it should significantly complement this app in that it is targeting primary infection risk.

There must be significant potential for linkage between information on primary infection spread and recommended actions during subsequent aphid multiplication.

A screenshot from the BYDV Assist app.

BYDV Assist: get started

1 Download the BYDV Assist app from the Apple or Android app store on to your device. Open the app and add a new field by pressing the + icon in the bottom right corner.

2 Input your field location - BYDV Assist uses a weather model which claims accuracy to 4km.

3 Select your drilling and emergence date - this is where the 170 day-degrees (DD) is calculated from.

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

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

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