The herbicide Asulox (asulam) has been given an emergency approval for use to control bracken from 1 July 2023, but only for England.
The Bracken Control Group (BCG), which announced the development, said decisions for other parts of the UK had not yet been made.
It is possible that there may be four different decisions, or if any approval is issued there may be different conditions attached in the separate parts of the UK.
An emergency authorisation for the use of Asulox was also issued last year. It mains the only recommended bracken control herbicide.
The details of the England-only approval will be issued later on Monday (19 June) following extensive campaigning by BCG and other industry groups.
It comes after Scottish farm leaders called for the 'urgent approval' of the herbicide this year due to the lack of alternatives.
And Brian Walker, a tenant farmer from Argyll, recently accused the Scottish government of "dragging its heels" on the issue of reauthorisation.
The tenant farmer said he had never before seen more cows coming off the hill this spring covered in ticks.
“The warm temperatures in the dead bracken over the winter months makes it the perfect place for them to survive and breed over winter," he said.
He said this was having a devastating impact on his livestock, adding: "Once an animal becomes a host for ticks, we have to use a chemical – like spot-on treatments used on cats and dogs – to get rid of them.
"If we don’t do this, it could lead to the animals getting seriously ill - redwater disease in cattle and louping ill in sheep are nasty diseases."
