Sugar beet farmers have been warned that a badly-timed spray of herbicides could damage their potential yields by up to 20pc – or even kill off young plants completely.

The British Beet Research Organisation (BBRO), based at the Norwich Research Park, has issued guidance to growers across East Anglia as part of its Brilliant Basics campaign.

It says chemical spray mixtures and timings must be tailored to the growth stages of individual beet varieties, and as much as 20pc of potential yield can be lost if sugar beet plants are weakened by herbicide damage and subsequent stress from pests, diseases or weather.

Growers were urged to check across their fields to see if the minimum growth stage had been reached before spraying emerging crops, as well as weighing up the risks from other factors including the weather.

Ches Broom, knowledge exchange manager for the BBRO, said: “A lot of people have two or three different varieties in the field, so if they don’t look at the growth stages of different varieties in different places they could do a lot of damage.

“If they just think: ‘It is a lovely sunny day and I am going to go and spray’ – but they have a got a variety with a slow start – they might knock back that variety if they spray too early. So it is about checking the growth of all the plants before you go out with the sprayer.

“You have got to get the timing right to make sure that the crop is ready for it. There are varietal differences in the growth stages, so watch the cotyledon growth in the early stages because any plant you damage early on is going to have a knock-on effect on yield. If you really get your mix wrong, you could burn it off completely and kill the plant because they can be very delicate at that stage.

“Growers also need to mark out where the varieties are in the field. They might change the seed in their drill in the field and off they go, and then they don’t know where the change happened. So put a marker there. Know what variety you have got and watch how it is growing This attention to detail will reap rewards in the future.”