Growers could expect demand for classified seed to rise when the new Potato Cyst Nematode (PCN) directive comes into force in July 2010. The changes to the directive, first ratified in Europe in 1969, were agreed in April after 15 years' discussion, explained the Scottish Agricultural Science Agency's Jon Pickup.

"Growers with both seed and ware crops will have to commit to their seed area before they plant as the rules governing a pre-crop soil test for PCN have changed," he said.

Previously only marketed seed required a pre-crop test, and this could not be planted on infested land. Under the new directive all land destined for seed would need testing, unless the seed was planted on the same premises as it was produced.

"This move will go a long way to increase the use of classified seed, since it will restrict the movement of farm-saved seed between holdings within the same business," said Dr Pickup.

Other proposed directive changes would bring fields destined for ware production within the scope of random PCN tests - 0.5% of total ware area must be tested each year.

Sample sizes would also increase, and both changes meant the cost of controls would rocket.

"Currently that's picked up by the taxpayer, but will industry be expected to contribute?" he asked.

The threat of Erwinia chysanthemi - or more specifically the species known as Dickeya dianthicola - might prompt a boost for seed grown under the Safe Haven Accreditation Scheme, suggested SCRI's Ian Toth.

Latest BPC-funded studies into the disease that was devastating crops across Europe showed it had been identified in at least 40 English crops.

"I'm not being over-dramatic about how serious this disease is - experts in at least 10 countries consider it an increasing problem. It's not a problem in Scotland - no cases have yet been found - but it is a threat. The best way to keep it out is to buy Safe Haven seed."