Sugar beet growers will not be able to use neonicotinoid-treated seed this spring after cold weather reduced the risk of virus yellows disease.

Low temperatures during February mean that only 8.37% of the national sugar beet area is forecast to be affected by virus yellows by the end of August 2021.

See also: Neonic sugar beet derogation unlikely to be triggered

This is below the 9% trigger threshold for growers to use Cruiser SB neonicotinoid-treated seed to combat the disease.

An independent forecast from Rothamsted Research also predicts that the first aphids which spread the virus will arrive in crops from 18 May.

This is much later than in 2020, when the first aphids were seen in crops in late March – and again means the risk of virus yellows is reduced.

Significant impact

A bulletin from the British Beet Research Organisation said: “Cold weather has had a significant impact on overwintering aphid populations.”

This had reduced aphid numbers and was likely to delay the date of their migration into the 2021 crop, it said on Tuesday (2 March)

“This is a very similar national forecast to that in 2018. Aphids were first recorded in crops in late May 2018. This is very welcome news for crops in 2021.”

Drilling into good seed-beds – as soon as possible after seed arrived on farm – would ensure beet crops established quickly, the bulletin said.

“Consequently, plants will be more mature, resilient, and resistant to the impact of virus when aphids finally arrive.”

Neonicotinoids are banned over concern that they are harmful to pollinating insects, including bees.

But both British Sugar and NFU Sugar had supported an emergency application for growers to use the chemicals as a last resort to combat virus yellows.

‘Best outcome’

British Sugar expects UK sugar production for the current 2020-21 crop to be 900,000t – well down on the previous year’s 1.19m tonnes.

This is due to wet weather and the severe impact of virus yellows which devastated crops.

But British Sugar agriculture director Peter Watson said the emergency situation in 2020 was unlikely to be repeated in 2021.

“Growing the crop without the neonicotinoid seed treatment as a result of the freezing weather is the best outcome,” he said.

“The application for emergency use of the seed treatment was just that – we committed to only treat the seed if the risk to the crop was significant.

“We have followed the science, using a proven model that has been in place for over 55 years, and minimised impact where possible.

“We will continue to work to progress our plans to tackle virus yellows without the need for neonicotinoids in future years.”

Monitoring crops

BBRO scientists will continue to monitor closely for aphids throughout the coming season.

A network of yellow water pan traps will be put in place to help assess aphid numbers related to thresholds that trigger applications of foliar insecticides.

In other news, an emergency authorisation has been issued for the use of Vydate 10G to control free-living nematodes in sugar beet.

The rate of use is 30g/100m for application at drilling up to 30 April 2021 – and growers must abide by label and stewardship scheme conditions.