Wheat bulb fly risk higher in north
The wheat bulb fly risk in northern England is higher than last year, but the overall risk in England remains relatively low, according to this year’s HGCA survey.
Wheat bulb fly is a pest that affects all cereals, except oats, and levels vary annually and in bad cases can result in yield losses as high as 50%. Eggs are laid in the summer and larvae hatch between January and March and invade shoots, which eventually die back to show “deadheart” symptoms of damage.
The annual HGCA autumn wheat bulb fly survey involves taking soil samples from 30 fields split across eastern and northern England, where the pest is historically most prevalent.
Of these 30 fields, 7% were classified as “high-risk” as they contained egg numbers greater than the suggested autumn-drilling seed treatment threshold of 250 eggs/sq m.
Caroline Nicholls, HGCA research and knowledge transfer manager, says that although the risk remains relatively low and below the long-term average, all the high-risk fields were in the northern region and growers located here should be a little more cautious this year.
“The survey findings indicated a very low risk to early-drilled crops in the eastern region, but it is important to remember that a lower threshold of 100 eggs/sq m applies when crops are drilled after November.
“In both regions, 40% of monitored sites were above this lower threshold and these sites are likely to benefit from an insecticide seed treatment.”
Eggs are laid in late summer in bare soils and the survey took samples from land that provided a good opportunity for adult wheat bulb flies to lay eggs – such as land previously used for root crops, early harvested crops or fallow.
