BYDV resistance – a ‘massively important’ breakthrough

BYDV pressure may not be as high in TAG agronomist Jon Bellamy’s area as some of the coastal hot spots across southern England, but he is taking no chances with the potentially devastating disease.

The less favourable topography and climate of Oxfordshire and Northamptonshire, together with the move to later drilling to combat blackgrass, reduces the risk of aphid migration into wheat crops but doesn’t remove it. Many crops will need one spray in a typical season.

Indeed, in a mild autumn/early winter almost any cereal-growing area in the UK can suffer damaging infections, and this is exacerbated in areas where early drilling remains the norm, where two or more sprays may be required in some years.

“Severe outbreaks of BYDV can result in large yield losses, but low-level damage can also leach profits,” says Jon. “With so much at stake, it is not surprising that we see an element of insurance spraying to control this virus.

“We are talking big money in terms of investment and there is a lot at risk. Getting hit by BYDV in the spring after spending thousands of pounds on crop establishment and inputs is disastrous.

“This autumn we were getting catches quite late, so it would have been easy to talk oneself into having to spray a second spray this autumn. Whether that would have been the right thing to do remains to be seen.”

Jon always discusses BYDV with his clients every year in some detail. “Most are well informed, but some people have become a bit blasé about it.

“We’ve had neonicotinoid seed dressings for years that gave us good control, and more recently later drilling because of blackgrass has helped, and people have got away with it.

“This winter has probably been cold enough to help us out, and perhaps some growers have been quite lucky in that respect. The trouble with BYDV is you don’t know until it’s too late.”

There are plenty of apps and decision support systems available but these only indicate whether the season is high or low risk.

“They will all inform you when T-sum 170 is reached, when the second generation of aphids is likely to be present,” says Jon.

“It is still up to the grower or their agronomists to check crops for aphids and decide whether to spray or not, it is really difficult and time consuming to inspect fields for aphids and be 100% confident there are none there, so we are back to square one.”

Genetics – the other way

While control of BYDV may appear fairly straightforward, agronomists hate using insecticides, says Jon. “It’s not just us, no farmers want to use an insecticide unless they absolutely have to.

“The first point when giving advice as a BASIS qualified agronomists is to ask whether you need the spray in the first place, or can you do it some other way.

“BYDV resistance in wheat opens the door to another way. It is massively important, not only in terms of management but from an environmental point of view.”

He believes sprays are often applied unnecessarily, not just because they are used as insurance but because probably only 25% of the aphid population is carrying BYDV.

“Spraying crops when there is no need is a real waste of energy, as is making and transporting the plant protection products required for the job,” says Jon.

“And it exposes beneficials and other non-target species to the insecticide, which no-one wants to do.”

Over-exposure of aphid vectors to pyrethroids, the main group of insecticides available to control the aphid vectors, also increases the likelihood of declining efficacy and eventual resistance, he believes. “It is widespread in grain aphids, and there are indications of resistance in bird cherry-oat aphids in Ireland.”

The £45/ha recently made available under stewardship for keeping areas of the farm insecticide free fits well with BYDV-resistant varieties. “I think this is good money and could be quite important,” says Jon. “Some growers might want to use BYDV-resistant varieties to help secure this payment, especially if end users get on board.”

Resistant varieties are a “huge step forward”, Jon concludes. “Everyone I speak in the industry is saying what a great trait to have coming along.

“I can’t wait until we have many more BYDV-resistant varieties. It will be such a help in managing our wheat crops, and so much more efficient too.”