12 January 1996

Brown rot threat makes going Dutch too risky?

By Robert Harris

POTATO growers planning to plant Dutch seed this spring are playing "Russian roulette", accor-ding to an international microbiologist. Not so, says the ministry.

Tom Stones, technical director of Potex in Hanley, Staffs, believes enough tubers are carrying brown rot bacteria to cause widespread infection of soils in the UK. Potato production in areas like East Anglia could be "wiped out", he maintains. "The system of dykes and drains used for irrigation is ideal for spreading the disease."

Although tubers are checked on leaving Holland and again in the UK, Mr Stones says tests are "only 90% sensitive". Enough infected tubers will slip through to pose a real threat, he insists.

He wants to see a ban on imports for at least a year until the degree of infection in Holland is independently assessed.

The ministry insists such a ban is not possible legally and is also unnecessary. "We are fairly satisfied with the restrictions put on at EU level," says a spokesman.

Only seed known to be free of the disease will be "passported" and tested in the Netherlands, and tougher inspections have been introduced. Importers also have to notify MAFF so tests can be conducted in the UK. "As far as I know, fingers crossed, they seem to be working."

The PMB, though not advising growers against using Dutch seed, stresses the test is not foolproof. "We have made the point no test can guarantee stock is free of bacteria," says R&D officer Mike Storey. Only 200 tubers are tested from each consignment of up to 25t. Infected tubers may be missed.

But MAFF is taking "a responsible attitude", he believes. "Individual growers have to decide if the risk is acceptable or not."

Ask seed companies to test seed again when it is delivered, he advises. Under National Assoc-iation of Seed Potato Merchants and Scottish Potato Trade Association conditions of sale there is a defect notification period of 14 days.

&#8226 Get supplier to re-test seed when delivered to farm.

&#8226 Monitor seed for unusual rots – report if found.

&#8226 Check growing crops for early wilting symptoms and test if any suspicions.