The whole of England and Wales is expected to become a bluetongue protection zone within weeks.
In a move auctioneers said could devastate autumn trade between Scotland and northern England, DEFRA announced the protection zone would be extended shortly to cover Northumberland and Cumbria, the only two regions of England currently outside the area.
However this would not happen before 1 September, unless new outbreaks of the disease were confirmed.
The Welsh Assembly government also announced the whole of Wales would become a protection zone, but this was unlikely to happen before Sunday, 31 August.
DEFRA said the advance notice allowed farmers to order vaccine and plan ahead of movement restriction.
Nigel Gibbens, chief veterinary officer, said the time of year and weather conditions meant there was an increased risk of bluetongue outbreaks in the UK.
“We are urging the industry to remain vigilant, and encouraging keepers to order vaccine as soon as possible,” he said. “Vaccination is the only way to protect your animals during this high-risk period.”
NFU Scotland said it was disappointed with the decision and said it had “significant implications” for cross-border trading in cattle and sheep this autumn.
Trade from Cumbria and Northumberland was very important to Scotland, with tens of thousands of calves traditionally moving across the border in the autumn, a spokesman said.
Traders and markets needed to use the advanced warning to make plans and limit the financial impact the extension of protection zone could have.
“We would have liked to have seen Cumbria and Northumberland enter the zone at the same time as Scotland, which is likely to be in the vector-free period in winter,” the spokesman said.
“However there is small window of opportunity for arrangements to be made to allow trade.
“Traders can move livestock into Scotland now and markets can start making private transactions.”
David Pritchard, Harrison and Hetherington livestock auctioneers operations director, said extension of the zones could devastate trade.
“About 30% of stock purchased in at our Carlisle market goes into Scotland, while the same amount of stock is brought from Scotland to be shown at the Carlisle markets,” he said.
“Some people have moved livestock to provide for specialist sales, but extending the zone in the autumn when a lot of stock gets moved is bound to have an effect on markets.
“We know it will cause a disruption and we can envisage it being a devastating situation.”