Growers were still overwhelmingly reliant on a single crop protection product for controlling sprout suppression in potatoes, an industry expert has warned.

Adrian Cunnington, who welcomed about 100 farmers and growers to a second annual industry storage forum at Sutton Bridge, near King's Lynn, said 1.9m tonnes of potatoes were treated by a single product.

A key sprout suppressant, CIPC, was used on 94pc of 1.85m tonnes of potatoes, which were stored after harvest, and destined mainly for the processing industry.

Mr Cunnington, who heads Sutton Bridge Crop Storage Research where �600,000 has been invested in facilities in the past couple of years, said the product was used on large volumes of the crop grown for processing and for some packing outlets.

'There is no current processing alternative,' he added.

When government challenged the industry's reliance on CIPC as part of the re-registration procedure in 2007, limits were set for minimum residue levels at 10mg per kg. In response, an industry-wide stewardship group was set up to work to retain this key sprout suppressant, said Mr Cunnington.

'CIPC is our strongest solution but it is also our biggest threat.'

The industry has responded by cutting residue limits to 3.6mg per kg active ingredient for the fresh market and for processing at 6.375mg.

'We need to be thinking about timing, we need to be thinking about dosage, about efficient application and disease risks. It is about common sense management and it is crucial,' said Mr Cunnington, who said �2.2m was funding eight projects on sprout suppression.

'We had a project on the use of CIPC in bulk stores and this has given us a huge step forward in reducing residue levels in processing potatoes.'

Other less effective control options included natural dormancy, temperature control in stores, a new formulation of spearmint oil and chemicals, including maleic hydrazide and ethylene.