Updated: Sep 22, 2021
Bird cherry aphid numbers have been building earlier this season than last, suggesting unprotected winter cereal crops could be at greater threat of barley yellow dwarf virus this autumn.
Latest data from Rothamsted Research’s Insect Survey shows a sharp rise in the numbers caught its nationwide network of 16 suction traps during the week ending 12 September.
“The increase is following the year-on-year trend but is happening a little earlier this year,” says Dr Cathy Hooper, technical sales manager at RAGT.
“In the south and south west, the bird cherry-oat aphid is the main vector for BYDV in winter cereals, so the higher numbers could lead to earlier and perhaps higher BYDV pressure.
“Growers who plan to drill in the next fortnight, or who already have crops in the ground, should keep a close eye out for aphids throughout the autumn, and longer if the weather remains mild.”
BYDV is a serious disease of wheat, barley and oats and, according to AHDB, 82% of the crop area is at risk from BYDV if left untreated. Wheat yield losses average 8% in untreated crops but can be as high as 60%.
“Now that seed treatments are no longer available to control the aphid vectors, growers are reliant on well-timed pyrethroid sprays to prevent infection if numbers reach threshold, unless they are growing a variety with BYDV resistance,” says Cathy.
Currently, the only resistant wheat variety available ln the UK is RGT Wolverine, which is widely available for sowing this autumn.
Resistance comes from the presence of the Bdv2 gene that originates from a wild goat grass. This offers protection from the day the wheat is planted to the day it is cut.
With no spraying necessary, RGT Wolverine growers only have to pay £15/ha for BYDV protection, assuming a seed rate of 175kg/ha, cheaper than buying a pyrethroid and applying it.
“The Bdv2 gene greatly simplifies crop management, removing the need to monitor and control aphid populations with foliar-applied insecticide sprays while benefiting the environment,” says Cathy.
More BYDV-resistant wheat varieties, milling and feed, are now making their way along the RAGT pipeline, she adds.
“These include some that feature orange wheat blossom midge resistance, bringing the prospect of insecticide-free wheat to many growers.”
* To find out more about BYDV resistance in wheats: please click here to see the RAGT fact sheet.