Think twice before you spray for BYDV

For many growers across the UK, the threat of BYDV is a familiar one, particularly after a very mild 2015 autumn led to some of the worst disease pressure seen for years in certain regions.

However, Nigel Adam, Development Manager for Seed Treatments at Bayer, warns that it is crucial growers do not respond to this pressure simply by applying pyrethroid sprays against the aphid vectors that spread the disease. As he points out, BYDV pressure is dependent on multiple factors that need to be kept in mind:

Nigel Adam.

“Drilling date, geographical location, weather, aphid pressure, seed rate, use of seed treatment – these will all influence the pressure the crop experiences and whether a follow-up spray might even be required,” he says. “For example, if you’re drilling Deter (clothianidin)-dressed seed at a higher seed rate in October, the Deter gives you protection for over ten weeks. So in a normal season, with average temperatures, subsequent sprays wouldn’t be needed to control aphids which spread BYDV.”

And with pyrethroid resistance in aphids an increasing problem, Mr Adam notes that it is imperative that growers think twice before spraying in order to ensure that they have access to the full toolkit of control measures for years to come.

“Taking a careful, considered approach to your BYDV control strategy, and particularly spraying, is beneficial from a time and cost point of view, beneficial for the environment, and also beneficial when it comes to addressing this issue of resistance.”

Agrii is launching a new BYDV Alert App, which it believes has the potential to help make the decision of whether a follow-up spray is needed. Developed over four years by Dr Francesca Salinari, the app provides Agrii agronomists with in-season tracking of aphid risk and reinforces Mr Adam’s suggestion that in recent seasons many growers would not have had to spray as much as expected.

“It is only during mild autumns and winters – like in 2015, when the temperature in November and December didn’t fall – that the BYDV risk in quite a few places around the UK can be significant enough that the majority of growers actually need to apply an insecticide on October-sown, Deter-treated seed,” says Dr Salinari.

“The app is all about timing. If you time when there’s a risk of BYDV spread, you can reduce the number of sprays and therefore keep the pressure of pyrethroid resistance in grain aphids from increasing. The app, along with other information like Rothamsted’s data on aphid migration, helps you have a proper integrated pest management strategy and a proper anti-resistance strategy. It’s not just done by the calendar or gut feeling – it allows you to help justify if there’s the need for a spray.”