Improved BYDV tool to give cereal growers better control
© Nigel Cattlin/Alamy Stock Photo Winter cereal growers are set to see a more accurate warning system next season for a key aphid-spread disease.
The AHDB’s new Acrobat tool will give a more precise forecast of the risk of barley yellow dwarf virus (BYDV), and could give growers a greater chance of claiming for a new environmental payout, earning an extra £45/ha for the non-use of insecticides.
The Acrobat model is designed to be more accurate than the current T-Sum method to detect a disease which, in bad infestions, can cut winter cereal yields by 1t/ha.
See also: 4 cultural techniques for controlling BYDV in cereals
Crop consultant Adas has been involved in developing the disease test, which the group’s lead entomologist, Dr Mark Ramsden, says is showing promising results from assessing the aphid threat in the autumn.
“Acrobat is a better model than T-Sum for assessing BYDV risk, and is more accurate for telling growers when to go and check their crops for aphids,” he tells Farmers Weekly.
This year’s mild autumn has led to an increased risk of aphids and hence the disease.
Research by Adas at The Morley Agricultural Foundation, in Norfolk, has shown a greater accuracy with the Acrobat system.
Initially, aphids which can transmit BYDV colonise relatively few crop plants, but a second generation of aphids tend to move away from these plants.
Bird cherry aphid infestation © Nigel Cattlin/Alamy Stock Photo
Controlling this generation is a key part of a BYDV management strategy.
On the Morley farm, winter wheat was drilled from 20 September to late October and early-sown crops started to emerge by the beginning of October on the 700ha independent research station, near Wymondham, between Thetford and Norwich, which farms on light sandy loam soils.
Model comparison
The two aphid tests were used side-by-side at Morley in the autumn on early-drilled crops.
The T-Sum test indicated a high risk of aphid flight in the last week of October, so an insecticide was applied on 5 November.
The T-sum assessment is calculated from the accumulated average daily air temperature, above a baseline temperature of 3C, from the date of crop emergence until a target of 170 is reached.
Then growers are advised to check crops for aphids and treat with a pyrethroid insecticide if the numbers are high.
In comparison, the Acrobat model showed a low risk of aphid flight on 3 November, and did not indicate that an insecticide spray might be necessary.
Like T-Sum, Acrobat uses cumulative temperatures, but it also assesses the presence of aphids – and, importantly, whether these aphids carry the virus.
The system uses data from Rothamsted Research, which surveys aphids in the autumn until the end of November.
The early November figure showed that 18% of aphids were carrying the virus.
Mark’s entomologist colleague at Adas, Dr Duncan Coston, says Acrobat is looking more accurate than T-Sum as it did not alert staff at Morley to examine crops in early November and, therefore, prevented non-essential insecticide spraying.
“The Acrobat system gives fewer trigger points for growers to go and observe their crops to evaluate if insecticide spraying is necessary,” he says.
Barley yellow dwarf virus in Craft winter barley © David Jones
Norfolk farm
Morley’s farm manager, David Jones, grows 200ha of winter wheat along with winter barley, winter oats and winter rye, and says the new test has promising potential.
“Acrobat could lead to better decision-making, especially for early-drilled crops,” he says.
Autumn 2023 was seen as a low pressure season for BYDV, with a low number of aphids seen on sticky traps after prolonged wet weather, and therefore no insecticides were deemed necessary.
That season, the UK’s most popular wheat variety Dawsum was compared with the BYDV-resistant variety Grouse.
As expected, Dawsum gave the higher yield, considering its high-yield potential in the absence of BYDV.
BYDV-resistant varieties such as Grouse tend to be lower yielding in the absence of BYDV, and although Grouse is not on the AHDB Recommended List (RL), the only BYDV-resistant RL varieties are Wolverine and Goldfinch, both lower yielding than top yielders.
Results with Grouse were inconclusive at harvest 2024 after a difficult growing year and low BYDV infection.
David is continuing to assess the variety, with 20ha of Grouse in the ground this season.
Most of his 200ha wheat area is in Dawsum and Extase. Only the early-drilled crops this autumn received a pyrethroid spray.
The later-drilled crops, which often followed sugar beet, were not sprayed.
The advent of these new BYDV resistant varieties – which are also resistant to orange wheat blossom midge – means that growers could qualify for the £45/ha a year on offer for non-insecticide use under the Sustainable Farming Incentive (CIPM4).
Barley yellow dwarf virus in oats © Nigel Cattlin/Alamy Stock Photo
Barley yellow dwarf virus
Barley yellow dwarf virus (BYDV) is a complex of viruses spread by aphids – including bird cherry-oat aphids and grain aphids – and is the most widely distributed viral disease of cereals.
The disease affects wheat, barley and oats, and early symptoms include a slight discolouration of the youngest leaves.
The plants grow slowly and the discolouration develops. Yield reductions in the most severe fields can be as much as 50%.
Later in the season, plants are clearly stunted, show extensive tillering, and there is a delay in heading and ripening resulting in grains being shrivelled.
The infection is usually patchy throughout the crop. Once symptoms appear, it is too late for control measures.
The disease was largely controlled by the neonicotinoid seed dressing clothiadin (Deter) until December 2018, when use was banned in cereals.
Other methods of control include:
- Delaying drilling until the main aphid migration period is over
- Cutting the potential source of aphid infection by destroying the green bridge of volunteer cereals and weeds with herbicides
- Using pyrethroid insecticides
- The arrival of new resistant varieties.
Wolverine – the first BYDV-resistant winter wheat variety – emerged a few years ago from plant breeder RAGT.
It was followed by Grouse and now Goldfinch, but they have shown lower yields than other leading varieties, when infection is low or insecticides have been applied.
Morley is the AHDB’s Strategy Cereal Farm East, and all those speaking to Farmers Weekly were attending a meeting at the farm in November 2024.
