Keeping BYDV in check: why variety choice and drilling date matter

There’s no single answer when it comes to BYDV. But there are several things we can control — from when we drill and how we manage volunteers, through to the varieties we choose and how we monitor aphid activity.

At ProCam, we’re encouraging growers to take an integrated approach this autumn, combining cultural controls, variety selection and targeted insecticide use to help keep BYDV pressure under control.

Start with the drilling date

One of the most effective ways to reduce BYDV risk is also one of the simplest: delay drilling where conditions and the rotation allow.

Crops that emerge during September and the first half of October are generally at the greatest risk of infection, as they are exposed to virus-carrying aphids during a period when populations can still be high.

Previous data shows that the risk of infection reduces significantly once crops emerge after mid-October. However, a later drilling date is not a guarantee of protection. If warm conditions continue into late autumn, aphid activity can also continue, leaving even later-emerging crops vulnerable.

We can’t control the weather, but we can control when we put crops in the ground. For growers in areas with a history of BYDV, it is therefore worth considering whether drilling can be pushed back without compromising establishment or the wider cropping programme.

Don’t give aphids a head start

Drilling date is only part of the picture. What happens between crops can also have a major influence on early BYDV pressure.

Volunteers and grass weeds can act as a green bridge, providing both food and habitat for aphids between cropping cycles. Wingless aphids can then move from these plants into newly emerging cereals, carrying the virus with them.

Removing this green bridge before drilling is therefore an important part of BYDV management.

Where possible, all cereal volunteers and grass weeds should be destroyed before the next crop is drilled. This is particularly important where cereals are being established into green cover.

Ideally, allow around five weeks between destroying volunteers and drilling the next cereal crop. This gives aphids time to die out rather than simply moving straight from the old crop into the new one.

Look beyond the highest yield on the Recommended List

Variety choice is another useful tool, particularly for growers farming in known BYDV hotspots.

It can be tempting to simply select the highest-yielding variety on the Recommended List (RL), but the variety that delivers the highest yield under ideal conditions isn’t necessarily the one that will perform best when BYDV pressure is high.

Historically, RL trials have not necessarily reflected performance under significant BYDV infection. That makes it important to consider the characteristics of individual varieties alongside their headline yield figures.

The good news is that genetic tolerance and resistance to BYDV are becoming increasingly available. Wheat varieties such as RGT Goldfinch, Griffin, Gorgon and Guardsman, alongside hybrid barley varieties such as SY Kestrel, give growers another tool to help manage the disease.

What our trials tell us

We’ve been putting some of these varieties to the test ourselves.

In a ProCam trial comparing 10 winter wheat varieties under BYDV pressure, the differences were significant. Varieties with proven genetic resistance consistently recorded BYDV infection levels below 10%, while infection in non-resistant varieties ranged from more than 30% to almost 50%.

That difference in infection also translated into yield.

In the insecticide-free trial, RGT Gorgon and RGT Guardsman both produced close to or above 10t/ha, while Champion yielded just over 7t/ha.

It’s an important reminder that variety choice needs to reflect the conditions a crop is actually likely to face. In a BYDV hotspot, a variety with genetic resistance or tolerance may offer considerably more protection against yield loss than simply choosing a variety for its performance under low-pressure conditions.

Monitor, assess and spray when needed

Even with good cultural controls and careful variety selection, growers should continue to monitor crops throughout the autumn.

The AHDB BYDV decision support tool can help growers assess when crops are most at risk from aphid activity and support decisions around insecticide applications.

Where an insecticide is required, product choice also matters. For example, Gocha (25 g/L esfenvalerate) can be considered as part of a BYDV management programme, with a lower impact on beneficial insects such as ladybirds than some other pyrethroids.

The aim shouldn’t be to automatically spray every crop. Instead, insecticide decisions should form part of an integrated approach based on crop development, aphid pressure, variety susceptibility and prevailing conditions.

Take a joined-up approach to BYDV

BYDV is a difficult pest to manage because the risk is influenced by weather, aphid populations, drilling dates, crop establishment and variety choice.

That makes an integrated approach particularly important.

Before drilling, consider:

• Can drilling be delayed to reduce the period of crop exposure?
• Have volunteers and grass weeds been effectively destroyed?
• Has enough time been allowed between removing the green bridge and drilling?
• Is the chosen variety suitable for the BYDV risk on the farm?
• How will aphid activity and crop risk be monitored through the autumn?
• What is the appropriate threshold for intervention?

There may be no way to eliminate BYDV risk completely, but there are plenty of steps growers can take to reduce it.

Speak to your local ProCam agronomist to discuss your BYDV risk this autumn and build a management strategy around your drilling date, variety choice, rotation and local conditions.